https://www.coastalwiki.org/w/api.php?action=feedcontributions&user=Katreineblomme&feedformat=atomCoastal Wiki - User contributions [en]2024-03-28T21:36:41ZUser contributionsMediaWiki 1.31.7https://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51596Al Hoceima coast2012-08-07T19:02:35Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
| width="20%" rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
| width="20%" |'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''''Article 10'''''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation values</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
|'''Climate change impacts'''<br />
|'''Article 22'''</br><br />
Natural Hazards<br />
|Within the framework of national strategies for integrated coastal zone management, the Parties shall develop policies for the prevention of natural hazards. To this end, they shall undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters, in particular of climate change.<br />
<br />
|-<br />
|rowspan="3" |'''Cross-cutting issues'''<br />
|'''Article 14'''</br><br />
Participation<br />
|1. With a view to ensuring efficient governance throughout the process of the integrated management of coastal zones, the Parties shall take the necessary measures to ensure the appropriate involvement in the phases of the formulation and implementation of coastal and marine strategies, plans and programmes or projects, as well as the issuing of the various authorizations, of the various stakeholders, including: the territorial communities and public entities concerned; economic operators; non-governmental organizations; social actors; the public concerned.<br />
Such participation shall involve inter alia consultative bodies, inquiries or public hearings, and may extend to partnerships.<br />
<br />
<br />
|-<br />
|'''Article 15'''</br><br />
Awareness-Raising, Training, Education and Research<br />
<br />
|1. The Parties undertake to carry out, at the national, regional or local level, awareness-raising activities on integrated coastal zone management and to develop educational programmes, training and public education on this subject.</br>2. The Parties shall organize, directly, multilaterally or bilaterally, or with the assistance of the Organization, the Centre or the international organizations concerned, educational programmes, training and public education on integrated management of coastal zones with a view to ensuring their sustainable development.</br>3. The Parties shall provide for interdisciplinary scientific research on integrated coastal zone management and on the interaction between activities and their impacts on coastal zones. To this end, they should establish or support specialized research centres. The purpose of this research is, in particular, to further knowledge of integrated coastal zone management, to contribute to public information and to facilitate public and private decision-making.<br />
<br />
<br />
|-<br />
|'''Article 27'''</br><br />
Exchange of Information and Activities of Common Interest<br />
|Define coastal management indicators, taking into account existing ones, and cooperate in the use of such indicators;<br />
|}<br />
<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
|valign="top"|'''Economic Indicator'''</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''</br><br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| valign="top"|'''Governance Indicator (01)'''</br><br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf.<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51595Al Hoceima coast2012-08-07T19:01:06Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
|rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''''Article 10'''''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation values</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
|'''Climate change impacts'''<br />
|'''Article 22'''</br><br />
Natural Hazards<br />
|Within the framework of national strategies for integrated coastal zone management, the Parties shall develop policies for the prevention of natural hazards. To this end, they shall undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters, in particular of climate change.<br />
<br />
|-<br />
|rowspan="3" |'''Cross-cutting issues'''<br />
|'''Article 14'''</br><br />
Participation<br />
|1. With a view to ensuring efficient governance throughout the process of the integrated management of coastal zones, the Parties shall take the necessary measures to ensure the appropriate involvement in the phases of the formulation and implementation of coastal and marine strategies, plans and programmes or projects, as well as the issuing of the various authorizations, of the various stakeholders, including: the territorial communities and public entities concerned; economic operators; non-governmental organizations; social actors; the public concerned.<br />
Such participation shall involve inter alia consultative bodies, inquiries or public hearings, and may extend to partnerships.<br />
<br />
<br />
|-<br />
|'''Article 15'''</br><br />
Awareness-Raising, Training, Education and Research<br />
<br />
|1. The Parties undertake to carry out, at the national, regional or local level, awareness-raising activities on integrated coastal zone management and to develop educational programmes, training and public education on this subject.</br>2. The Parties shall organize, directly, multilaterally or bilaterally, or with the assistance of the Organization, the Centre or the international organizations concerned, educational programmes, training and public education on integrated management of coastal zones with a view to ensuring their sustainable development.</br>3. The Parties shall provide for interdisciplinary scientific research on integrated coastal zone management and on the interaction between activities and their impacts on coastal zones. To this end, they should establish or support specialized research centres. The purpose of this research is, in particular, to further knowledge of integrated coastal zone management, to contribute to public information and to facilitate public and private decision-making.<br />
<br />
<br />
|-<br />
|'''Article 27'''</br><br />
Exchange of Information and Activities of Common Interest<br />
|Define coastal management indicators, taking into account existing ones, and cooperate in the use of such indicators;<br />
|}<br />
<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
|valign="top"|'''Economic Indicator'''</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''</br><br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| valign="top"|'''Governance Indicator (01)'''</br><br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf.<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51594Al Hoceima coast2012-08-07T18:59:51Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
|rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''''Article 10'''''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation values</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
|'''Climate change impacts'''<br />
|'''Article 22'''</br><br />
Natural Hazards<br />
|Within the framework of national strategies for integrated coastal zone management, the Parties shall develop policies for the prevention of natural hazards. To this end, they shall undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters, in particular of climate change.<br />
<br />
|-<br />
|rowspan="3" |'''Cross-cutting issues'''<br />
|'''Article 14'''</br><br />
Participation<br />
|1. With a view to ensuring efficient governance throughout the process of the integrated management of coastal zones, the Parties shall take the necessary measures to ensure the appropriate involvement in the phases of the formulation and implementation of coastal and marine strategies, plans and programmes or projects, as well as the issuing of the various authorizations, of the various stakeholders, including: the territorial communities and public entities concerned; economic operators; non-governmental organizations; social actors; the public concerned.<br />
Such participation shall involve inter alia consultative bodies, inquiries or public hearings, and may extend to partnerships.<br />
<br />
<br />
|-<br />
|'''Article 15'''</br><br />
Awareness-Raising, Training, Education and Research<br />
<br />
|1. The Parties undertake to carry out, at the national, regional or local level, awareness-raising activities on integrated coastal zone management and to develop educational programmes, training and public education on this subject.</br>2. The Parties shall organize, directly, multilaterally or bilaterally, or with the assistance of the Organization, the Centre or the international organizations concerned, educational programmes, training and public education on integrated management of coastal zones with a view to ensuring their sustainable development.</br>3. The Parties shall provide for interdisciplinary scientific research on integrated coastal zone management and on the interaction between activities and their impacts on coastal zones. To this end, they should establish or support specialized research centres. The purpose of this research is, in particular, to further knowledge of integrated coastal zone management, to contribute to public information and to facilitate public and private decision-making.<br />
<br />
<br />
|-<br />
|'''Article 27'''</br><br />
Exchange of Information and Activities of Common Interest<br />
|Define coastal management indicators, taking into account existing ones, and cooperate in the use of such indicators;<br />
|}<br />
<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
| '''Economic Indicator'''</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''</br><br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| '''Governance Indicator (01)'''</br><br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf.<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51593Al Hoceima coast2012-08-07T18:57:04Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
|rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''''Article 10'''''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation values</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
|'''Climate change impacts'''<br />
|'''Article 22'''</br><br />
Natural Hazards<br />
|Within the framework of national strategies for integrated coastal zone management, the Parties shall develop policies for the prevention of natural hazards. To this end, they shall undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters, in particular of climate change.<br />
<br />
|-<br />
|rowspan="3" |'''Cross-cutting issues'''<br />
|'''Article 14'''</br><br />
Participation<br />
|1. With a view to ensuring efficient governance throughout the process of the integrated management of coastal zones, the Parties shall take the necessary measures to ensure the appropriate involvement in the phases of the formulation and implementation of coastal and marine strategies, plans and programmes or projects, as well as the issuing of the various authorizations, of the various stakeholders, including: the territorial communities and public entities concerned; economic operators; non-governmental organizations; social actors; the public concerned.<br />
Such participation shall involve inter alia consultative bodies, inquiries or public hearings, and may extend to partnerships.<br />
<br />
<br />
|-<br />
|'''Article 15'''</br><br />
Awareness-Raising, Training, Education and Research<br />
<br />
|1. The Parties undertake to carry out, at the national, regional or local level, awareness-raising activities on integrated coastal zone management and to develop educational programmes, training and public education on this subject.</br>2. The Parties shall organize, directly, multilaterally or bilaterally, or with the assistance of the Organization, the Centre or the international organizations concerned, educational programmes, training and public education on integrated management of coastal zones with a view to ensuring their sustainable development.</br>3. The Parties shall provide for interdisciplinary scientific research on integrated coastal zone management and on the interaction between activities and their impacts on coastal zones. To this end, they should establish or support specialized research centres. The purpose of this research is, in particular, to further knowledge of integrated coastal zone management, to contribute to public information and to facilitate public and private decision-making.<br />
<br />
<br />
|-<br />
|'''Article 27'''</br><br />
Exchange of Information and Activities of Common Interest<br />
|Define coastal management indicators, taking into account existing ones, and cooperate in the use of such indicators;<br />
<br />
|}<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
| '''Economic Indicator'''</br><br />
</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''<br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| '''Governance Indicator (01)'''<br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51592Al Hoceima coast2012-08-07T18:55:28Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
|rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''''Article 10'''''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation values</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
|'''Climate change impacts'''<br />
|'''Article 22'''</br><br />
Natural Hazards<br />
|Within the framework of national strategies for integrated coastal zone management, the Parties shall develop policies for the prevention of natural hazards. To this end, they shall undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters, in particular of climate change.<br />
<br />
|-<br />
|rowspan="3" |'''Cross-cutting issues'''<br />
|'''Article 14'''</br><br />
Participation<br />
|1. With a view to ensuring efficient governance throughout the process of<br />
the integrated management of coastal zones, the Parties shall take the necessary measures to ensure the appropriate involvement in the phases of the formulation and implementation of coastal and marine strategies, plans and programmes or projects, as well as the issuing of the various authorizations, of the various stakeholders, including: the territorial communities and public entities concerned; economic operators; non-governmental organizations; social actors; the public concerned.<br />
Such participation shall involve inter alia consultative bodies, inquiries or public hearings, and may extend to partnerships.<br />
<br />
<br />
|-<br />
|'''Article 15'''</br><br />
Awareness-Raising, Training, Education and Research<br />
<br />
|1. The Parties undertake to carry out, at the national, regional or local level, awareness-raising activities on integrated coastal zone management and to develop educational programmes, training and public education on this subject.</br>2. The Parties shall organize, directly, multilaterally or bilaterally, or with the assistance of the Organization, the Centre or the international organizations concerned, educational programmes, training and public education on integrated management of coastal zones with a view to ensuring their sustainable development.</br>3. The Parties shall provide for interdisciplinary scientific research on integrated coastal zone management and on the interaction between activities and their impacts on coastal zones. To this end, they should establish or support specialized research centres. The purpose of this research is, in particular, to further knowledge of integrated coastal zone management, to contribute to public information and to facilitate public and private decision-making.<br />
<br />
<br />
|-<br />
|'''Article 27'''</br><br />
Exchange of Information and Activities of Common Interest<br />
|Define coastal management indicators, taking into account existing ones, and cooperate in the use of such indicators;<br />
<br />
|}<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
| '''Economic Indicator'''</br><br />
</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''<br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| '''Governance Indicator (01)'''<br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51591Al Hoceima coast2012-08-07T18:52:39Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
|rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''''Article 10'''''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
|'''Climate change impacts'''<br />
|'''Article 22'''</br><br />
Natural Hazards<br />
|Within the framework of national strategies for integrated coastal zone management, the Parties shall develop policies for the prevention of natural hazards. To this end, they shall undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters, in particular of climate change.<br />
<br />
|-<br />
|rowspan="3" |'''Cross-cutting issues'''<br />
|'''Article 14'''</br><br />
Participation<br />
|1. With a view to ensuring efficient governance throughout the process of<br />
the integrated management of coastal zones, the Parties shall take the necessary measures to ensure the appropriate involvement in the phases of the formulation and implementation of coastal and marine strategies, plans and programmes or projects, as well as the issuing of the various authorizations, of the various stakeholders, including: the territorial communities and public entities concerned; economic operators; non-governmental organizations; social actors; the public concerned.<br />
Such participation shall involve inter alia consultative bodies, inquiries or public hearings, and may extend to partnerships.<br />
<br />
<br />
|-<br />
|'''Article 15'''</br><br />
Awareness-Raising, Training, Education and Research<br />
<br />
|1. The Parties undertake to carry out, at the national, regional or local level, awareness-raising activities on integrated coastal zone management and to develop educational programmes, training and public education on this subject.</br>2. The Parties shall organize, directly, multilaterally or bilaterally, or with the assistance of the Organization, the Centre or the international organizations concerned, educational programmes, training and public education on integrated management of coastal zones with a view to ensuring their sustainable development.</br>3. The Parties shall provide for interdisciplinary scientific research on integrated coastal zone management and on the interaction between activities and their impacts on coastal zones. To this end, they should establish or support specialized research centres. The purpose of this research is, in particular, to further knowledge of integrated coastal zone management, to contribute to public information and to facilitate public and private decision-making.<br />
<br />
<br />
|-<br />
|'''Article 27'''</br><br />
Exchange of Information and Activities of Common Interest<br />
|Define coastal management indicators, taking into account existing ones, and cooperate in the use of such indicators;<br />
<br />
|}<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
| '''Economic Indicator'''</br><br />
</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''<br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| '''Governance Indicator (01)'''<br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51590Al Hoceima coast2012-08-07T18:48:07Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
|rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''''Article 10'''''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
|'''Climate change impacts'''<br />
|'''Article 22'''</br><br />
Natural Hazards<br />
|Within the framework of national strategies for integrated coastal zone management, the Parties shall develop policies for the prevention of natural hazards. To this end, they shall undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters, in particular of climate change.<br />
|}<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
| '''Economic Indicator'''</br><br />
</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''<br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| '''Governance Indicator (01)'''<br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51589Al Hoceima coast2012-08-07T18:46:34Z<p>Katreineblomme: </p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
|rowspan="3" |'''Urban sprawl and Coastal Planning'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
|(f) The formulation of land use strategies, plans and programmes covering urban development and socio-economic activities, as well as other relevant sectoral policies, shall be required.<br />
<br />
|-<br />
<br />
|'''''Article 11'''''<br />
Coastal Landscapes<br />
|1. The Parties, recognizing the specific aesthetic, natural and cultural value of coastal landscapes, irrespective of their classification as protected areas, shall adopt measures to ensure the protection of coastal landscapes through legislation, planning and management.<br />
<br />
|-<br />
|'''''Article 23'''''<br />
Coastal Erosion<br />
|2. The Parties, when considering new activities and works located in the coastal zone including marine structures and coastal defence works, shall take particular account of their negative effects on coastal erosion and the direct and indirect costs that may result. In respect of existing activities and structures, the Parties should adopt measures to minimize their effects on coastal erosion.<br />
<br />
|-<br />
|rowspan="3"|'''Coastal resources management'''<br />
|'''''Article 6'''''</br><br />
General Principles of Integrated Coastal Zone Management<br />
<br />
|(i) Preliminary assessments shall be made of the risks associated with the various human activities and infrastructure so as to prevent and reduce their negative impact on coastal zones.</br>(ii) to ensure that fishing practices are compatible with sustainable use of natural marine resources;</br>(b) All elements relating to hydrological, geomorphological, climatic, ecological, socio-economic and cultural systems shall be taken into account in an integrated manner, so as not to exceed the carrying capacity of the coastal zone and to prevent the negative effects of natural disasters and of development.</br>(d) Appropriate governance allowing adequate and timely participation in a transparent decision-making process by local populations and stakeholders in civil society concerned with coastal zones shall be ensured.</br> <br />
<br />
|-<br />
|'''Article 9'''</br><br />
Economic Activities<br />
<br />
|(d) ensure that the coastal and maritime economy is adapted to the fragile nature of coastal zones and that resources of the sea are protected from pollution;</br>(d) Tourism, sporting and recreational activities,</br>(i) to encourage sustainable coastal tourism that preserves coastal ecosystems, natural resources, cultural heritage and landscapes;</br>(ii) to promote specific forms of coastal tourism, including cultural, rural and ecotourism, while respecting the traditions of local populations;</br>(e) Utilization of specific natural resources, to regulate the extraction of sand, including on the seabed and river sediments or prohibit it where it is likely to adversely affect the equilibrium of coastal ecosystems;</br>(iii) to monitor coastal aquifers and dynamic areas of contact or interface between fresh and salt water, which may be adversely affected by the extraction of underground water or by discharges into the natural environment.</br><br />
<br />
|-<br />
|'''Article 10'''<br />
Specific Coastal Ecosystems<br />
|2. Marine habitats</br><br />
(a) adopt measures to ensure the protection and conservation, through<br />
legislation, planning and management of marine and coastal areas, in<br />
particular of those hosting habitats and species of high conservation</br>3. Coastal forests and woods</br><br />
The Parties shall adopt measures intended to preserve or develop coastal forests and woods located, in particular, outside specially protected areas.</br> <br />
4. Dunes</br><br />
The Parties undertake to preserve and, where possible, rehabilitate in a sustainable manner dunes and bars. <br />
<br />
<br />
<br />
|-<br />
<br />
|}<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
| '''Economic Indicator'''</br><br />
</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''<br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| '''Governance Indicator (01)'''<br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Al_Hoceima_coast&diff=51588Al Hoceima coast2012-08-07T18:33:49Z<p>Katreineblomme: table</p>
<hr />
<div>[[Image:Al_Hoceima_Coast_map.jpg|380px|thumb|left]]<br />
<br />
<br />
<br />
<u>'''CASE description'''</u> <br />
<br />
The coast of Al Hoceima is located in the central part of the northern of Morocco, along the Mediterranean Sea. Two large units can be distinguished within the Coast: <br />
Al Hoceima Bay (marked by a large alluvial plain),<br />
Al-Hoceima National park, (45 kilometres of coastline) characterised by some of the highest rocky cliffs in the whole of the Mediterranean.<br />
<br />
[[Image:Al_Hoceima_Coast1.jpg|300px|thumb|right|Coastal erosion (Author: Mohamed El Andaloussi)]]<br />
<br />
<br />
<u>'''ICZM phase'''</u><br />
<br />
[[ICZM_Process_diagram/Setting the vision|Setting the vision]]<br />
<br />
<br />
<br />
<br />
<br />
<br />
<u>'''Main coastal issues'''</u><br />
<br />
* Urban sprawl and Coastal Planning<br />
<br />
* Coastal resources management<br />
<br />
* Climate change impacts<br />
<br />
<br />
<u>'''Relation between coastal issues and the ICZM protocol principles and articles.'''</u><br />
<br />
The following articles and principles of the ICZM protocol are relevant for the work carried out in our CASE:<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
!Issue<br />
!Articles<br />
!Principles<br />
<br />
|-<br />
<br />
|}<br />
<u>'''Relevance of coastal issues'''</u><br />
<br />
The diagnosis established during the previous steps has highlighted that the major economic activities in the area are tourism, fisheries and agriculture. The three identified issues are significant for productivity and sustainability of all these sectors. Indeed, the degradation and decline of coastal resources has affected the well being of the local population and has led to an increase of unemployment and to a large migration to Europe. The predictive impacts of climate change and sea-level rise is likely to exacerbate these impacts.<br />
<br />
Previous studies carried-out at Al Hoceima coast and its National Park within the context of the CAMP-Morocco project has retained the following Sustainability indicators, according to the availability of data and based on a participatory process, proxies and expert judgment:<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;" <br />
| '''Economic Indicator'''</br><br />
</br><br />
1. Amount of fisheries</br><br />
2. Value of fishery products</br><br />
3. Number of tourist arrivals</br><br />
4. Number of tourist nights</br><br />
5. Average length of stay of tourists</br><br />
6. Duration of the tourist season</br><br />
<br />
| '''Environmental Indicator (13)'''</br><br />
7. Forest cover</br><br />
8. Quality of bathing water</br><br />
9. % of beaches prohibited to bathing</br><br />
10. Coastal erosion (shoreline retreat)</br><br />
11. Access rate to drinking water</br><br />
12. % Connection to sewerage network in urban areas</br><br />
13. % of treated wastewater</br><br />
14. % of waste collected</br><br />
15. % of waste collected and recycled</br><br />
16. Urbanization rate</br><br />
17. Sensitive marine species</br><br />
18. Weighted score of marine sites</br><br />
19. Weighted score of sensitive habitats</br><br />
<br />
<br />
|-<br />
<br />
| '''Socio-cultural Indicator (07)'''<br />
7. International emigration of local people</br><br />
8. Internal emigration</br><br />
9. Rate of coastal development</br><br />
10. Urbanized coastline</br><br />
11. Population density</br><br />
12. Rate of population growth</br><br />
13. Human Development Index (HDI)</br><br />
<br />
| '''Governance Indicator (01)'''<br />
Number of environmental projects</br><br />
<br />
|}<br />
<br />
For more details on this report please visit: <br />
http://www.pap-thecoastcentre.org/pdfs/WEB%20Analyse%20de%20Durabilite.pdf<br />
These indicators will be confronted with the selected PEGASO set of indicators<br />
<br />
<br />
<u>'''Objectives'''</u><br />
<br />
<br />
* To remediate to the coastal degradation in order to sustain common ecosystem services supporting economic welfare and social wellbeing.<br />
<br />
* To elaborate future Scenarios based on a participatory process and using quantified Indicators.<br />
<br />
* To assess coastal vulnerability to climate change and propose adaptation strategies.<br />
<br />
* To help decision makers in their decisions regarding the implementation of the ICZM protocol through the integration of all the tools results, the use of Multi-Criteria Analysis and the production of integrative maps (GIS) easily readable by the stakeholders.<br />
<br />
<br style="clear:both;"/><br />
<br />
[[Image: Al_Hoceima_Coast2.jpg|300px|thumb|left|Landscape values (Author: Hocein Bazaïri)]]<br />
<br />
<u>'''End Products'''</u><br />
<br />
<br />
* Diagnosis analysis <br />
<br />
* Environmental Territorial Diagnosis (ETD) <br />
<br />
* Set of ICZM Indicators<br />
<br />
* Vulnerability maps to sea-level rise<br />
<br />
* Prospective analysis using scenarios and indicators<br />
<br />
* Designation of a DSS for coastal managers and planners, using a Multi-Criteria Analysis (MCA)<br />
<br />
<br />
<u>'''Tools developed and used'''</u><br />
<br />
Indicators - Participation <br />
<br />
<u>'''Other tools to be applied'''</u><br />
<br />
Vulnerability assessment <br />
<br />
<u>'''CASE Responsibles'''</u> <br />
<br />
Maria Snoussi, Hocein Bazaïri - University Mohamed V – Agdal <br />
<br />
email: ma_snoussi@yahoo.fr - hoceinbazairi@yahoo.fr<br />
<br />
<br />
<span style="color: Blue"><small>Elaboration: Stefano Soriani, Fabrizia Buono, Monica Camuffo, Marco Tonino, University Ca’ Foscari of Venice.</small></span></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Bathing_suitablility_test.jpg&diff=50439File:Bathing suitablility test.jpg2012-07-30T07:12:56Z<p>Katreineblomme: </p>
<hr />
<div></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Water_quality.jpg&diff=50289File:Water quality.jpg2012-07-25T08:54:16Z<p>Katreineblomme: uploaded a new version of "Image:Water quality.jpg"</p>
<hr />
<div></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Water_quality.jpg&diff=50288File:Water quality.jpg2012-07-25T08:53:42Z<p>Katreineblomme: uploaded a new version of "Image:Water quality.jpg"</p>
<hr />
<div></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Boat_traffic_.jpg&diff=50275File:Boat traffic .jpg2012-07-25T08:41:59Z<p>Katreineblomme: </p>
<hr />
<div></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Fisheries.jpg&diff=50274File:Fisheries.jpg2012-07-25T08:39:58Z<p>Katreineblomme: </p>
<hr />
<div></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Water_quality.jpg&diff=50272File:Water quality.jpg2012-07-25T08:37:17Z<p>Katreineblomme: </p>
<hr />
<div></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Urban_sprawl.jpg&diff=50269File:Urban sprawl.jpg2012-07-25T08:31:26Z<p>Katreineblomme: </p>
<hr />
<div></div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50265Biogenic reefs of Europe and temporal variability2012-07-25T08:21:35Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
[[Image:coastal and shelf habitats.jpg|thumb|center|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
<br />
'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see Figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa |more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. ''Sabellaria spinulosa'' reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
<br />
</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
<br />
<br />
<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on ''Sabellaria alveolata'' maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''''S. alveolata abundance'''''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50264Biogenic reefs of Europe and temporal variability2012-07-25T08:18:06Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
[[Image:coastal and shelf habitats.jpg|thumb|center|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
<br />
'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see Figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa |more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. ''Sabellaria spinulosa'' reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
<br />
</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
<br />
<br />
<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on ''Sabellaria alveolata'' maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''''S. alveolata abundance'''''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50263Biogenic reefs of Europe and temporal variability2012-07-25T08:17:16Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
[[Image:coastal and shelf habitats.jpg|thumb|center|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
<br />
'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see Figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa |more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. Sabellaria spinulosa reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
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</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
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<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
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<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on ''Sabellaria alveolata'' maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''''S. alveolata abundance'''''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50262Biogenic reefs of Europe and temporal variability2012-07-25T08:16:08Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
[[Image:coastal and shelf habitats.jpg|thumb|center|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
<br />
'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see Figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa |more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. Sabellaria spinulosa reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
<br />
</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
<br />
<br />
<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on ''Sabellaria alveolata'' maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''S. alveolata abundance'''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
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{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Changing_occurence.jpg&diff=50261File:Changing occurence.jpg2012-07-25T08:06:04Z<p>Katreineblomme: uploaded a new version of "Image:Changing occurence.jpg"</p>
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<div>Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010.</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Changing_occurence.jpg&diff=50260File:Changing occurence.jpg2012-07-25T08:05:13Z<p>Katreineblomme: uploaded a new version of "Image:Changing occurence.jpg": Reverted to version as of 08:03, 25 July 2012</p>
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<div>Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010.</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Changing_occurence.jpg&diff=50259File:Changing occurence.jpg2012-07-25T08:04:38Z<p>Katreineblomme: uploaded a new version of "Image:Changing occurence.jpg": Reverted to version as of 08:03, 25 July 2012</p>
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<div>Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010.</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Changing_occurence.jpg&diff=50258File:Changing occurence.jpg2012-07-25T08:04:14Z<p>Katreineblomme: uploaded a new version of "Image:Changing occurence.jpg": Reverted to version as of 08:03, 25 July 2012</p>
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<div>Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010.</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Changing_occurence.jpg&diff=50257File:Changing occurence.jpg2012-07-25T08:03:37Z<p>Katreineblomme: uploaded a new version of "Image:Changing occurence.jpg": Reverted to version as of 08:21, 5 July 2012</p>
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<div>Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010.</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Changing_occurence.jpg&diff=50256File:Changing occurence.jpg2012-07-25T08:03:26Z<p>Katreineblomme: uploaded a new version of "Image:Changing occurence.jpg"</p>
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<div>Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010.</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50252Dynamics, threats and management of biogenic reefs2012-07-25T07:19:53Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
<br />
Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
<br />
Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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</br><br />
[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|Figure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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</br><br />
==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
<br />
Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
<br />
</br><br />
==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
<br />
Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of ''M. edulis'' are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
<br />
</br><br />
==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). ''M. modiolus'' in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
<br />
</br><br />
<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
<br />
</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
<br />
The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
<br />
</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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===='''''Sabellaria spinulosa'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
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===='''''Sabellaria alveolata'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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===='''''Mytilus spp.'''''====<br />
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Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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===='''''Modiolus modiolus'''''====<br />
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In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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== SEE ALSO ==<br />
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[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
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[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
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[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
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==REFERENCES ==<br />
<references/><br />
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[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
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{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50251Dynamics, threats and management of biogenic reefs2012-07-25T07:18:38Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
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==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
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As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
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Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
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Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|Figure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata (L.)''. '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
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Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
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''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of ''M. edulis'' are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
<br />
</br><br />
==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). ''M. modiolus'' in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
<br />
</br><br />
<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
<br />
</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
<br />
The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
<br />
</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
<br />
</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50249Dynamics, threats and management of biogenic reefs2012-07-25T07:17:47Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
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==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
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As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
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Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
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Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|Figure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata (L.)''. '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
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Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
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''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of ''M. edulis'' are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
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''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
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==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
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''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
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</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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There is insufficient information available on chemical threats to ''M. modiolus''. <br />
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</br><br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
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</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
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In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
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The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
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Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
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===CURRENT MANAGEMENT PRACTICES===<br />
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Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
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In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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</br><br />
===='''''Sabellaria spinulosa'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
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</br><br />
===='''''Sabellaria alveolata'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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</br><br />
===='''''Mytilus spp.'''''====<br />
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Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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</br><br />
===='''''Modiolus modiolus'''''====<br />
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In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
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[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50247Dynamics, threats and management of biogenic reefs2012-07-25T07:16:47Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
<br />
Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
<br />
Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
<br />
</br><br />
[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|Figure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata (L.)''. '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
<br />
Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
<br />
Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
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==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
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==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
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In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
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'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
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'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
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'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
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===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
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''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
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{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
<br />
</br><br />
<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
<br />
</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
<br />
The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
<br />
</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50246Dynamics, threats and management of biogenic reefs2012-07-25T07:16:10Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
<br />
Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
<br />
Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
<br />
</br><br />
[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|Figure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
<br />
</br><br />
==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata (L.)''. '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
<br />
Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
<br />
</br><br />
==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
<br />
Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
<br />
</br><br />
==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
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</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
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In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
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The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
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Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
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</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50245Dynamics, threats and management of biogenic reefs2012-07-25T06:58:42Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
<br />
Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
<br />
Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|Figure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
<br />
Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
<br />
</br><br />
==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
<br />
</br><br />
<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
<br />
</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
<br />
The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
<br />
</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
<br />
</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
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[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
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==REFERENCES ==<br />
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[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
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{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50244Dynamics, threats and management of biogenic reefs2012-07-25T06:57:42Z<p>Katreineblomme: </p>
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==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
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As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
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Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
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Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|FFigure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
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Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
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''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
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''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
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==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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There is insufficient information available on chemical threats to ''S. alveolata''.<br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
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</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
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</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
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</br><br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
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</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
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The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
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</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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</br><br />
===='''''Sabellaria spinulosa'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50243Dynamics, threats and management of biogenic reefs2012-07-25T06:57:26Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
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As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). ''S. spinulosa'' occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
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Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
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Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|FFigure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
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Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
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''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
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''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
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==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
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''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
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</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
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</br><br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
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</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
<br />
The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
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</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
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Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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</br><br />
===='''''Sabellaria spinulosa'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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</br><br />
===='''''Mytilus spp.'''''====<br />
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Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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</br><br />
===='''''Modiolus modiolus'''''====<br />
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In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=File:Figure_salt-marsh_zonation.JPG&diff=50234File:Figure salt-marsh zonation.JPG2012-07-24T17:48:38Z<p>Katreineblomme: uploaded a new version of "Image:Figure salt-marsh zonation.JPG"</p>
<hr />
<div>Typical salt-marsh zonation (modified from Bertness ''et al.'', 2002. Species along the tidal elevation gradient are adapted to the inundation frequency, including extreme flooding and storm events.</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50233Biogenic reefs of Europe and temporal variability2012-07-24T14:32:17Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
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Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
[[Image:coastal and shelf habitats.jpg|thumb|center|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
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'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see Figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa |more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. Sabellaria spinulosa reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
<br />
</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
<br />
<br />
<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on Sabellaria alveolata maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''S. alveolata abundance'''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50232Dynamics, threats and management of biogenic reefs2012-07-24T14:22:07Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
<br />
</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
<br />
''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
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As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). S. spinulosa occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
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Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
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Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|FFigure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
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Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
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''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
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''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
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==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
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''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from ([http://www.marlin.ac.uk the Marine Life Information Network website]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
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</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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There is insufficient information available on chemical threats to ''M. modiolus''. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
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</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
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In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
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The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
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Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
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===CURRENT MANAGEMENT PRACTICES===<br />
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Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
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In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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</br><br />
===='''''Sabellaria spinulosa'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
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</br><br />
===='''''Sabellaria alveolata'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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</br><br />
===='''''Mytilus spp.'''''====<br />
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Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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</br><br />
===='''''Modiolus modiolus'''''====<br />
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In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
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[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
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==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50231Dynamics, threats and management of biogenic reefs2012-07-24T14:18:48Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). S. spinulosa occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
<br />
Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
<br />
Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
<br />
</br><br />
[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|FFigure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
<br />
Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
<br />
Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
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==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
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==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
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In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from the Marine Life Information Network website ([http://www.marlin.ac.uk]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
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'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
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'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
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'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
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===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
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''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
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{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
<br />
</br><br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
<br />
</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
<br />
The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
<br />
</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50230Dynamics, threats and management of biogenic reefs2012-07-24T14:15:31Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). S. spinulosa occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
<br />
Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
<br />
Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
<br />
</br><br />
[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|FFigure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
<br />
</br><br />
==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
<br />
Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
<br />
</br><br />
==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
<br />
Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
<br />
</br><br />
==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from the Marine Life Information Network website ([http://www.marlin.ac.uk]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
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===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
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In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
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The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
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Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
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===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
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In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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===='''''Sabellaria spinulosa'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
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</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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</br><br />
===='''''Modiolus modiolus'''''====<br />
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In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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</br><br />
== SEE ALSO ==<br />
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[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
<br />
==REFERENCES ==<br />
<references/><br />
</br><br />
</br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50229Dynamics, threats and management of biogenic reefs2012-07-24T14:14:09Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
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==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). S. spinulosa occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
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Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
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Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|FFigure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
<br />
Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36 (3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
<br />
''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
<br />
</br><br />
==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
<br />
''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from the Marine Life Information Network website ([http://www.marlin.ac.uk]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
<br />
The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
<br />
The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
<br />
</br><br />
====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''M. modiolus''. <br />
<br />
</br><br />
<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
<br />
</br><br />
===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
<br />
In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
<br />
The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
<br />
Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
<br />
Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
<br />
</br><br />
<br />
===CURRENT MANAGEMENT PRACTICES===<br />
<br />
Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
<br />
In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<br />
Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
<br />
</br><br />
== SEE ALSO ==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
<br />
[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
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==REFERENCES ==<br />
<references/><br />
</br><br />
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[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
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{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50228Biogenic reefs of Europe and temporal variability2012-07-24T14:03:55Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
[[Image:coastal and shelf habitats.jpg|thumb|right|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
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Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
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[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see Figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa |more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
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The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
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[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
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''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
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''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. Sabellaria spinulosa reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
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'''''Intertidal Mytilus edulis'''''</br><br />
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The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
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</br><br />
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[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
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''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
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==Examples of temporal variability==<br />
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'''''Sabellaria alveolata'''''<br />
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Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
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Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
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{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on Sabellaria alveolata maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''S. alveolata abundance'''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
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Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
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<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50226Biogenic reefs of Europe and temporal variability2012-07-24T14:01:49Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
[[Image:coastal and shelf habitats.jpg|thumb|right|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see Figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. Sabellaria spinulosa reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
<br />
</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
<br />
<br />
<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on Sabellaria alveolata maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''S. alveolata abundance'''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
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[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
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Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_dunes&diff=50225Dynamics, threats and management of dunes2012-07-24T13:55:26Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
==Processes and mechanisms driving natural dynamics & ecosystem development==<br />
[[Image: sand dunes.JPG|thumb|right|350px| Figure 1: Dune section.]]<br />
<br />
Coastal sand [[dunes]] are aeolian landforms, found along the majority of the world’s [[coast]]. This [[ecosystem]] located at the spatial transition between terrestrial and marine environments, can be found in coastal areas where a supply of sand‐sized material (within the size range 0.2-2.0 mm) is available to be transported by winds. The coastal dune system is composed of the 3 compartments: the submerged beach, the emerged beach and the dune. These 3 compartments, under permanent exchanges, must be considered as a whole (Figure 1). Coastal morphodynamic variability is caused by a variety of factors ranging from climate and climate variability, relative sea level, [[sediment]] supply, vegetation, and coastal dynamics at global, regional, and local scales. Due to these factors, the coastal zone is a highly dynamic environment at temporal scales ranging from wind bursts and wave breaking (seconds to minutes), to storm and growing seasonal variability (days to seasons), to interannual climate variability and sea level fluctuations (years to centuries, etc). The genesis of an aeolian dune is divided in three phases (Clemmensen ''et al.'', 2001<ref name= "Clem" >CLEMMENSEN L. B., PYE K., MURRAY A., and HEINEMEIER J., 2001. Sedimentology, stratigraphy, and landscape evolution of a Holocene coastal dune system, Lodbjerg, NW Jutland, Denmark. ''Sedimentology'', '''48''': 3-27.</ref>): (1) dune field formation; (2) accumulation of sediment deposits; and (3) preservation of the deposited sediments. In order for coastal dune formation to begin, there must be both adequate sediment availability and sufficient wind energy capable of transporting this sand landward (Aagard ''et al.'', 2007<ref>AAGARD T., ORFORD J., and MURRAY A.S., 2007. Environmental controls on coastal dune formation; Skallingen Spit, Denmark. ''Geomorphology''. '''83''', 29-47.</ref>). After the initial formation of the dune field deposits, accumulation of sand occurs when the influx of sediment is greater than the losses, creating a positive sediment budget. Finally, the third phase of preservation of sediments occurs when the dune system is stabilized either by the ground‐water table rising or the growth of vegetation (Clemmensen ''et al.'', 2001<ref name= "Clem"/>), or a change in other climatic factors (Tsoar, 2005<ref>TSOAR H., 2005. Sand dunes mobility and stability in relation to climate. ''Physica A'', '''357''': 50‐56. </ref>). Vegetation is necessary to trap the sand in order to make for dune growing, but also to stabilize the ground. The pioneer [[species]], by this action, will facilitate the establishment of other species (less tolerant of salinity, wind…), increasing [[biodiversity]] richness (flora and fauna). A variety of factors affect the availability of sediment for dune formation, including changes in sea level, changes in sediment transport from continental and oceanic sources, and the presence of vegetation, as well as the impacts of human activities. In addition, the variability of the wind, both in the direction and magnitude, can play an important role in the mobilization and landward transport of sediment. The interactions between all of these forcing factors produce a variety of different environments in which dune formation may occur. <br />
<br />
<br />
==Vulnerability & threats==<br />
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During the last thirty years, almost 75% of Mediterranean coastal [[dunes]] have been damaged or destroyed, principally by [[tourism]] (Géhu, 1985; Salman & Strating, 1992; in Van Der Meulen & Salman, 1993<ref>Salman, Strating, 1992. '''In:''' VAN DER MEULEN F. And SALMAN A.H.P.M., 1993. Gestion des dunes côtières de Méditerranée. ''The first International Conference on the Mediterranean Coastal Environment''. 167‐183.</ref>). There are different kinds of destruction causes. First, the natural vents which are eroded by storms or/and [[sea level rise]], overwash, and sea flooding events. The [[vulnerability]] of coastal dunes to flooding depends on the characteristics of the dune system itself: height, width, conservation status etc. It also depends on the intensity and impact of the event (e.g. sea level rise, storm intensity). The taller dunes are more resistant to flooding but possibly more susceptible to erosion while the shorter dunes might be more vulnerable to flooding. In the next century, climate change will lead to a rise of mean sea‐level, a likely increase of storms intensity and frequency and a more contrasted distribution of wetness between winter and summer (GIECC 2001, 2007, in Vinchon ''et al.'', 2008<ref>GIECC 2001, 2007. '''In:''' VINCHON C., BALOUIN Y., IDIER D., GARCIN M., MALLET C., 2008. La réponse du trait de côte au changement climatique: Evolution des risqué côtiers en Aquitaine et en Languedoc‐Roussillon dans le siècle à venir. The littoral : challenge, dialogue, action. Lille-France. 11pp.</ref>). These changes will modify the coastal erosion and sea‐flooding hazards. Dune dynamics are driven by naturally occurring disturbances, which can be both common and recurrent. However, when these disturbances increase in intensity or frequency or when they are removed, there can be substantial alterations in community dynamics (Martinez and Psuty, 2004<ref>MARTINEZ M.L. and PSUTY N.P., 2004. Coastal Dunes. Ecology and Conservation. ''Ecological Studies''. '''171''', 386pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70677 ww.vliz.be/imis]</ref>). Dunes are thought to be fragile because only a slight disruption (either natural or human induced) may lead to change and long‐term progressive alteration (Carter, 1988<ref>CARTER R.W.G., 1988. Coastal environments. An introduction to the physical, ecological and cultural systems of the coastlines. Academic Press, New York.617pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=11046 ww.vliz.be/imis]</ref>) and their natural diversity might be compromised easily.</br><br />
<br />
For thousands of years, human activities have been impacting the coastal environment of the Mediterranean Basin through agriculture, husbandry and the deliberate use of fire. In recent decades, tourism has caused important damages on coastal landscapes with the urbanization of the coast, the increase of summer visitors, and the introduction of invasive or exotic species. The most heavily affected [[habitats]] are the sandy coastal systems and coastal dunes in particular (Tzatzanis ''et al.'', 2003<ref>TZATZANIS M., WRBKA T., SAUBERER N., 2003. Landscape and vegetation responses to human impact in sandy coasts of Western Crete, Greece. J. Nat. Conserv. '''11''', 187‐195.</ref>). The pedestrian and motorized pathways all over dunes lead to vegetation destruction and therefore enhanced weathering and erosion (Moulis and Barbel, 1999<ref>MOULIS D., and BARBEL P., 1999. Restauration des dunes. Réhabilitation et gestion des dunes littorals Méditerranéennes Françaises. Collection: Manuels et Méthodes. BRGM Ed., 75-91.</ref>). Waste deposits and [[invasive species]] introduction are also destruction factors. The potential for dune recovery is dependent on the sediment supply in each area and on the intensity of human impact. Dune plants are especially sensitive to disturbance and are heavily affected by humans. Without dune plants, the integrity and preservation of a stable dune complex cannot exist. [[Anthropogenic]] impacts combined with the natural regression process of the coastline induce the acceleration of the destruction of the dune vegetation (Araujo ''et al.'', 2002<ref>ARAUJO R., HONORADO J., GRANJA H. M., NEVES DE PINTO S., BARRETO CALDA F., 2002. Vegetation complexes of coastal sand dunes as an evaluation instrument of geomorphologic changes in the coastline. Littoral 2002, The changing Coast: 337-339. EUROCOAST/EUCC, Porto-Portugal : 337‐339.</ref>) ultimately leading to to dune destruction.<br />
<br />
<br />
==Key processes to focus on for maintaining ecosystems integrity==<br />
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Damaged coastlines are not attractive locations for tourism or leisure. Dune system vulnerability is defined as a set of conditions producing an acceleration of the erosion rhythm and system degradation. It is really important to not block natural processes which could destroy the system (Bodéré ''et al.'', 1991<ref>BODERE J.C., CRIBB R., CURR R., DAVIES P., HALLEGOUET B., MEUR C., PIRIOU N., WILLIAMS A., YONI C., 1991. La gestion des milieux dunaires littoraux. Evaluation de leur vulnérabilité à partir d’une liste de contrôle. Etude de cas dans le sud du Pays de Galles et en Bretagne occidentale. Norois n°151. Poitiers-France. 279‐298.</ref>) and to take into consideration the entire dune system with [[beach]] and [[foreshore]]. The natural dune- rebuilding process can take several years, and it may be desirable to rebuilding a storm-eroded dune quicker than natural processes O’Connell, 2008). Dune damaging accelerates sand transit inland and then this sand cannot nourish the beach anymore (Pinot, 1998). <br />
<br />
There are different ways to protect or restore dunes. Firstly, the protection of wildlife is important because fauna and flora are an integral part of dune system: vegetation stabilizes sand, whereas fauna control plant growth and interactions. Sand dunes provide a unique wildlife habitat. We must limit the trampling of visitors by paths and beach access setting up with fences. People walk through the dune because it is difficult to go on the sand. As they are looking for a hard surface to walk, we must provide them one. A marked pathway (by fences and why not with educative panels) is already a dissuasion.</br><br />
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In case of dune landscape restoration, totally or partially destroyed, it could be necessary to stimulate natural vegetation regeneration by planting indigenous species, and preferably plants characteristic for the first step of dune colonisation: builder sand plants like ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=403902 Ammophila arenaria]'', or ''Elymus fractus'' because they permit sand stabilization and input. Moreover, it is fundamental to avoid invasive species and to limit them when there are already here.</br><br />
<br />
The protection of implanted root native vegetation against wind erosion with weed permeable fences (“ganivelles”) and biodegradable geotextiles (Heurtefeux ''et al.'', 2007)<ref name= "Heurt">HEURTEFEUX H., GROSSET S., RICHARD P., SIRE E., 2007. Restoring a highly damaged site: Canet-en-Roussillon (Western French Mediterranean coast). ''ICCD'', 2007. Montpellier-France. 7pp.</ref><ref name= "Heurt2">HEURTEFEUX H., GROSSET S., VALANTIN P.‐Y., 2007. Une approche alternative de la gestion des risqué côtiers, l’exemple de la Petite Camargue. Territoires en movement 2007‐1. Les risqué côtiers. 11pp.</ref> is also a priority.</br><br />
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Another action of dune rehabilitation could be sand input to ensure dune system dynamics. The nourishment of the lowest part of the white dune will restore a homogeneous altimetry of the dune barriers in order to make it less sensitive to natural aggressions (waves and marine wind), and to limit the risk of marine submersion. This must be adapted to the [[morphology]] of the dune with consideration for the [[sensitivity]] of the natural environment (Heurtefeux ''et al.'', 2007<ref name= "Heurt"/><ref name= "Heurt2"/>).</br> <br />
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<br />
==Current management practises==<br />
[[Image: Policy options.JPG|thumb|right|350px| Figure 2: Policy options for coastal management (European Commission, 2004 ; in Heurtefeux ''et al.'', in press<ref name= "in press">HEURTEFEUX H., SAUBOUAP., LANZELLOTTIP., BICHOT A., 2011, in press. Coastal risk management modes: The managed realignment as a risks conception more integrated. Montpellier-France.)</ref>]]<br />
<br />
According to Heurtefeux ''et al.'' (in press)<ref name= "in press"/>, there are different coastal management modes which have been used and are yet to be employed. In the last twenty years, four global approaches to manage coasts have been developed (Figure 2). First, there is the approach by holding the line. It has persisted to be used. Traditionally, the goal is to protect developed area by using hard structures (Klein ''et al.'', 2001). The “do the minimum” approach corresponds to the use of natural processes to reduce risks but permitting coast natural changes. Some of the techniques used with this approach attempt to limit rather than to stop coastal erosion and cliff’s retreat. The “do nothing“ approach, which is rare but can be found is one of the more famous cases of “do nothing” approach is the municipality of Happisburg, in the county of North Norfolk (UK). The storm waves reached the coast with important damages on the bottom of the cliff, the cliff fell with major impact on the houses which were totally destroyed. Do nothing is one of the policies adopted when it is too late, when any decision has been thought of before, when the cost benefit analysis shows than the defence front to the sea exceeds the value of the properties. Finally, the Managed Realignment (M.R.) approach is quite recent. Its definitions and its particularities will be presented below.</br><br />
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The M.R.’s aim is to avoid heavy structures to respect dune‐beach system and its intrinsic transfers in order not to damage ecosystem functionalities. It’s necessary to consider dune-beach system in its totality, and thus its natural capacity to return at an initial state after a perturbation.</br><br />
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There are many special features of Managed Realignment. One of these features is to move back the economic assets on the coast to the hinterland. It is also to create a new defence line behind the beach and facing the sea to restore natural areas and to create a buffer between the sea and the economic assets. Another feature is to avoid the construction of new economic assets in areas where they would be vulnerable (Heurtefeux ''et al.'', in press<ref name= "in press"/>).</br><br />
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==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
<br />
[[dune erosion]]<br />
<br />
[[Dune stabilisation]]<br />
<br />
[[Sand_dunes |Sand dunes in Europe]]<br />
==References==<br />
<references/></br><br />
<br />
<br />
[[Category: Coastal defence]]<br />
[[Category: Biodiversity and habitat loss]]<br />
[[Category:Sand dunes]]<br />
<br />
<br />
{{ 4Authors<br />
|AuthorID1=15248<br />
|AuthorFullName1= Heurtefeux, Hugues<br />
|AuthorID2=20727<br />
|AuthorFullName2= Milor, Mercedes<br />
|AuthorID3=24380<br />
|AuthorFullName3=Bichot, Amandine<br />
|AuthorID4=20726<br />
|AuthorFullName4= Grosset, Stéphanie<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50223Biogenic reefs of Europe and temporal variability2012-07-24T13:50:55Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
[[Image:coastal and shelf habitats.jpg|thumb|right|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria alveolata'''''</br><br />
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''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. Sabellaria spinulosa reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
<br />
</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
<br />
<br />
<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on Sabellaria alveolata maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''S. alveolata abundance'''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
'''''Sabellaria spinulosa'''''<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Biogenic_reefs_of_Europe_and_temporal_variability&diff=50222Biogenic reefs of Europe and temporal variability2012-07-24T13:49:57Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
== European-scale distribution of biogenic reefs==<br />
[[Image:coastal and shelf habitats.jpg|thumb|right|250px|Figure 1: Map taken from the OSPAR Status Report 2010 <ref name= "OSPAR"/> depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]<br />
<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms. They do not share an uniform structure and are found at variable spatial scales. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', <br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'',<br />
''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140480 Mytilus edulis]''. Many [[Natural_barriers#Biogenic_reefs|biogenic reefs]] habitats are currently threatened and/or are in decline in Europe as a result of various natural and [[anthropogenic]] pressures (OSPAR 2010<ref name= "OSPAR"> OSPAR, 2010. Quality Status Report 2010. OSPAR Commission. London. 176 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=198817 www.vliz.be/imis]</ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br><br />
<br />
<br />
[[Image:S. salveolata .jpg|thumb|right|250px|Figure 3: Current OBIS distribution data for ''S. alveolata'' in Europe (data from OBIS, July 2012) showing distributions and unconfirmed records: red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria alveolata'''''</br><br />
<br />
''Sabellaria alveolata'' (or honeycomb worm) is a sedentary tube-dwelling polychaete (or annelid worm). They use suspended sediment to construct their tubes, see figure 2 (Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. ''Journal of the Marine Biological Association of the UK''. '''51''', 509-580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis]</ref>). This polychaete is most commonly found in colonies. There are two major forms of colonies: veneers sand reefs ([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]].)<br />
[[Image:Sabellaria salveolata .jpg|thumb|center|250px|Figure 2: Sabellaria alveolata<ref>[http://www.marinespecies.org/aphia.php?p=image&pic=1769 worms-website]</ref>.]]<br />
<br />
The records of ''Sabellaria alveolata'' throughout Europe are greater in northern latitudes (Figure 3). This is an obvious artifact of data reporting to OBIS as ''S. alveolata'' has been reported to be widely distributed in the France, Spain and Portugal and extends as far south as Morocco (Gruet, 1982<ref name ="Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata (Linné)'', Université des Sciences et Techniques, Nantes, France. PhD </ref>; Cunningham ''et al.'', 1984<ref name = "Cunning">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of ''Sabellaria alveolata'' (L.) in England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on ''Sabellaria alveolata'' colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22. </ref>). It reaches its northern limits in Britain but is restricted to the warmer waters off the west coast, as growth is inhibited below 5°C (Crisp, 1964<ref>CRISP D.J. 1964. The effects of the severe winter of 1962-63 on marine life in Britain. ''Journal of Animal Ecology.'' '''33''', 165-210.</ref>). The current confirmed northern limit is the Dumfriesshire coast of SW Scotland with records needing confirmation from the Firth of Clyde and Outer Hebrides. This species builds the largest reefs on the European coast; in particular the “Les Hermelles” reef in the Saint-Michael Bay in France, which is over 100 ha and is considered the largest reef in Europe (Gruet, 1982<ref name= "Gruet"/>; Marchand and Cazoulat, 2003 <ref>MARCHAND Y., CAZOULAT R., 2003. Biological reef survey using spot satellite data classification by cellular automata method ‐Bay of Mont Saint‐Michel (France). ''Computers & Geosciences''. '''29''', 413‐421.</ref>). <br />
</br><br />
<br />
<br />
[[Image:S. spinulosa .jpg|thumb|right|250px|Figure 4: Current OBIS distribution data for ''S. spinulosa'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Sabellaria spinulosa'''''</br><br />
<br />
''Sabellaria spinulosa'' (or Ross worm) is a tube-dwelling polychaeta closely related to ''Sabellaria alveolata''. It is a relatively disturbance-tolerant pioneers species (Jackson and Hiscock, 2008<ref>ckson, A., Hiscock, K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 28/04/2010]. Available from:[http://www.marlin.ac.uk/speciessensitivity.php?speciesID=4278 www.marlin.ac.uk]</ref>). In contrast to ''Sabellaria alveolata'', it mostly occurs in solitary or small aggregations. However, it can be gregarious under favorable conditions, forming large reef-structures (upto 30 cm high) (Hendrick and Foster-Smith, 2006<ref>Hendrick, V.J., Foster-Smith, R.L., 2006. ''Sabellaria spinulosa'' reef: a scoring system for evaluating 'reefiness' in the context of the Habitats Directive. ''Journal of the Marine Biological Association of the United Kingdom''. '''86''', 665-677.</ref>). The tubes are upright and typically consist of several layers of sediment particles([[Natural_barriers#Biogenic reefs#Species and Characteristics#Sabellaria spinulosa | more info]]). <br />
<br />
''Sabellaria spinulosa'' reefs are known from all European coasts, except the Baltic and the waters of the Kattegat and Skagerrak, but are typically limited to areas with very high levels of suspended sediment (OSPAR 2010 <ref name= "OSPAR" />, Figure 4). In the UK aggregations of ''S. spinulosa'' are reported to occur at a number of locations around the British Isles (Holt ''et al.'', 1998<ref name= "Holt"> HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. ''Scottish Association for Marine Science'' (UK Marine SACs Project). 170 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=142113 www.vliz.be/imis]</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology.'' '''370''', 35-40. </ref>). Perhaps the best known example of an ''S. spinulosa'' reef in the UK is found in the mouth of the Wash (east coast of England), where reefs are elevated above the seafloor and have been found to extend over hundreds of square meters within the Norfolk Coast SAC (Foster‐Smith and Hendrick, 2003<ref>FOSTER‐SMITH R.L., HENDRICK V.J., 2003. Sabellaria spinulosa reef in The Wash and North Norfolk cSAC and its approaches: Part III, Summary of knowledge, recommended monitoring strategies and outstanding research requirements. ''English Nature Research Reports'' Number 543. </ref>). Relatively few records have been found in Scotland (Figure 4). Not all of these aggregations could be described as “reefs”, for instance where the species may only form superficial crusts on mixed substrata. On the German coast, [[intertidal]] and [[subtidal]] reefs have been reported from the Wadden Sea (Berghahn and Vorberg, 1993<ref>BERGHAHN R., VORBERG R., 1993. Effects of the shrimp fisheries in the Wadden Sea. '''In''': Influence of fisheries upon Marine Ecosystems. Einfluss Der Fischerei Auf Marine Oekosysteme Lukowicz, M., 103-126.</ref>) and from the southern [[North Sea]] where Linke (1951)<ref> LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u. Volk.'' '''81''', 77‐84. </ref> reported reefs up to 60 cm thick, 8 m wide and 60 m long. ''S. spinulosa'' has also been reported from the French coast, but without precise locations (Holt ''et al.'', 1998 <ref name= "Holt"/>). <br />
<br />
</br><br />
<br />
'''''Intertidal Mytilus edulis'''''</br><br />
<br />
The distribution of ''Mytilus edulis'' (or common mussel) is circumpolar in boreal and temperate waters, in both the southern and northern hemispheres extending from the Arctic to the Mediterranean in the north‐east Atlantic (Soot‐Ryen 1955<ref>SOOT‐RYEN T., 1955. A report on the family Mytilidae. Allan Hancock Pacific Expedition. '''20''', 1-154.</ref>). The majority of intertidal beds are found in the Wadden Sea (Netherlands, Germany and Denmark) where a 2007 inventory reported an estimated coverage of 1865 hectares in the Dutch sector (Goudswaard ''et al.'', 2007 <ref>GOUDSWAARD P.C., JANSEN J.M.J., VAN ZWEEDEN C., KESTELOO J.J., VAN STRAALEN M.R., 2007. Het mosselbestand en het areaal aan mosselbanken op de droogvallende platen in de Waddenzee in het voorjaar van 2007. ''Wageningen IMARES'', December 2007. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=118353 www.vliz.be/imis]</ref>). It is also present in British coastal waters, Ireland (Jones ''et al.'', 2000 <ref name= "Jones">JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>) and there is a large bed (covering approximately 200 ha) in southern Brittany in France (Rollet ''et al.'', 2005 <ref>ROLLET C., BONNOT-COURTOIS C., FOURNIER J., 2005. Cartographie des habitats benthiques médiolittoraux à partir des orthophotographies littorales. Fiche technique-Projet REBENT FT13-2005-01, Ifremer, Brest. 18pp. </ref>).<br />
<br />
</br><br />
<br />
[[Image:Modiolus modiolus .jpg|thumb|right|250px|Figure 5: Current OBIS distribution data for ''Modiolus modiolus'' in Europe (data from OBIS, July 2012): red>101; orange=51-100; yellow=11-50; green=6-10; blue=1-5. Please note that older records and those from southern Europe are probably missing.]]<br />
'''''Modiolus modiolus'''''</br><br />
<br />
''Modiolus modiolus'' (or horse mussel) is an Arctic-boreal species that is limited in distribution by warmer temperatures to the south, but occasionally specimens have been reported as far south as Northwest Africa. It occurs from the Bay of Biscay to northern Norway, with occurrences off Iceland and the Faeroes (Tebble, 1966<ref>TEBBLE N., 1966. British bivalve seashells. Natural History Museum, London. pp 212.</ref>; Poppe & Gotö, 1993<ref>POPPE G., GOTO Y., 1993. ''European seashells''. Volume:2 (Scaphopoda, Bivalvia, Cephalopoda). Conchbooks, Haekenheim. 221 pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21430 www.vliz.be/imis]</ref>). It is found throughout British waters, but has most frequently been reported in northern and western areas (Figure 5). Extensive horse mussel beds are found only in parts of north and western Scotland, the Ards Peninsula, Strangford Lough, the Isle of Man, north-west Anglesey and north of the Lleyn Peninsula. <br />
<br />
Descriptions of ''M. modiolus'' usually state the presence of aggregated clumps on mud or muddy‐gravel sediments, although the vast majority of these will not fall into the definition of biogenic reef, due to low density and coverage. However, several areas do contain large beds definable as biogenic reef including beds in Strangford Lough (Roberts, 1975), the Isle of Man (Jones, 1951; unpublished references in Holt ''et al.'', 1998<ref name= "Holt"/>), Scottish waters (Comely 1978 <ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167‐193.</ref>; Howson ''et al.'', 1994<ref>HOWSON C., CONNOR D., HOLT R., 1994. The Scottish sealochs - an account of surveys undertaken for the Marine Nature Conservation Review. ''Joint Nature Conservation Committee Report'', No. 164.</ref>) and within the Lleyn Peninsula (Lindenbaum ''et al.'', 2008<ref>LINDENBAUM C., BENNELL J., REES E., MCCLEAN D., COOK W., WHEELER A., SANDERSON W., 2008. Small-scale variation within a ''Modiolus modiolus'' (Mollusca: Bivalvia) reef in the Irish Sea: I. Seabed mapping and reef morphology. ''Journal of the Marine Biological Association of the UK''. '''88''', 133-141.</ref>). One notable area of horse mussel beds that has received significant research are those within the Bay of Fundy on the Scotian Shelf, Canada (see Wildish ''et al.'',2009 <ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157 170.</ref>).<br />
<br />
<br />
<br />
==Examples of temporal variability==<br />
<br />
'''''Sabellaria alveolata'''''<br />
<br />
Cunningham ''et al.'' (1984)<ref name= "Cunning"/> reviewed the distribution and local abundance of ''S. alveolata'' in Britain. This review used past records from the literature, data from new shore surveys and reports via correspondence from other marine scientists. As a result of this exercise, changes in the extent of ''S. alveolata'' distribution over a period of approximately 100 years were documented. In order to evaluate the long-term temporal variability in ''S. alveolata'' distribution and abundance, the data were divided into three arbitrary periods: pre-1963 (before the cold winter of 1962/1963), 1964-1979 and 1980-1984 (Cunningham ''et al.'', 1984<ref name= "Cunning"/>). </br><br />
<br />
Frost ''et al.'' (2005)<ref name ="Frost">FROST M.T., LEAPER R., MIESZKOWSKA N., MOSCHELLA P., MURUA J., SMYTH C., HAWKINS S.J., 2005. Recovery of a Biodiversity Action Plan Species in Northwest England: possible role of climate change, artificial habitat and water quality amelioration. A report submitted to ''English Nature'', spring 2004.</ref> carried out a series of broadscale and focused mapping studies of ''S. alveolata'' in NW England and North Wales in 2003/04. This comprised a resurvey of sites that had been previously surveyed in the 1980s (Cunningham ''et al.'' 1984<ref name= "Cunning"/>). ''S. alveolata'' was found to be present at most of the sites where it had previously been recorded (e.g. Cunningham, 1984<ref name= "Cunning"/>) and at many of these sites it appears also to have increased in [[abundance]] (Table 1). ''S. alveolata'' had re-appeared in areas where it has been absent for many years (Table 1: Hilbre Island and Colwyn Bay) and had spread to areas for which there are no known previous records (Table 1: North Wirral, Rossal Point).</br><br />
<br />
Hawkins (1993) suggested that ''S. alveolata'' was declining along the Cumbrian coast, but the present study found it to be abundant or super‐abundant at most sites. The records from the present study therefore seem to confirm the observation made by others that ''S. alveolata'' shows a great deal of temporal variability within a fairly constant geographic range (e.g. Cunningham et. al., 1984<ref name= "Cunning"/>). Even on a shore where ''S. alveolata'' is continually present, there is a great deal of variability in terms of abundance and ‘within shore’ distribution. For example, long term studies at Duckpool in North Cornwall (Wilson 1971<ref name= "Wilson71"/>; 1974<ref>WILSON D.P., 1974. ''Sabellaria'' Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393-436.</ref>; 1976<ref>WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the<br />
Marine Biological Association of the United Kingdom''. '''56''', 305-310. <br />
</ref>) and in Normandy, France (Gruet, 1986<ref>GRUET Y., 1986. Spatio‐temporal changes of Sabellarian reefs built by the sedentary polychaete ''Sabellaria alveolata'' (Linn6) P.S.Z.N.I. ''Mar. Ecol.'' '''7'''(4), 303‐319.</ref>) have revealed a great deal of variability over the years in the distribution and abundance of'' S. alveolata'' colonies within sites.<br />
<br />
<br />
<br />
{|border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 1: Past data on Sabellaria alveolata maximum abundance in Northwest England and Wales, with recent resurveys included. N = absent, R = rare, O = occasional, F = frequent, C = common, A = abundant and SA = super-abundant (massive reefs). P = recorded as present but abundance not known. From Cunningham ''et al.'' (1984)<ref name= "Cunning"/> and Frost ''et al.'' 2005)<ref name= "Frost"/>.'''</span><br />
|-<br />
! style="text-align: left;" |Location<br />
! colspan="4" |'''S. alveolata abundance'''<br />
<br />
|-<br />
<br />
| <br />
|'''Pre-1963'''<br />
|'''1964-1979'''<br />
|'''1980-1984'''<br />
|'''2003-2004'''<br />
<br />
|-<br />
<br />
| Penmon <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Great Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Little Orme’s Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Rhos-on-Sea <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Colwyn Bay <br />
|P<br />
|<br />
|N<br />
|R<br />
<br />
|-<br />
<br />
| Hilbre Island <br />
|A<br />
|R<br />
|N<br />
|A<br />
<br />
|-<br />
<br />
| Wirral Foreshore <br />
|<br />
|<br />
|<br />
|A<br />
<br />
|-<br />
<br />
| Lytham Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| St Annes Pier <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Fleetwood,Rossall Pt <br />
|<br />
|<br />
|N<br />
|F<br />
<br />
|-<br />
<br />
| Heysham* <br />
|F-O<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
| Holme Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Humphrey Head <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Wadhead, Scar <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Walney Island <br />
|<br />
|<br />
|N<br />
|N<br />
<br />
|-<br />
<br />
| Annaside Bank <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Tarn Bay <br />
|<br />
|<br />
|A-SA<br />
|SA<br />
<br />
|-<br />
<br />
| Drigg <br />
|<br />
|<br />
|A<br />
|SA<br />
<br />
|-<br />
<br />
| Seascale <br />
|<br />
|<br />
|O<br />
|SA<br />
<br />
|-<br />
<br />
<br />
| Sellafield <br />
|<br />
|<br />
|O<br />
|A-SA<br />
<br />
|-<br />
<br />
| Nethertown <br />
|<br />
|<br />
|A<br />
|A<br />
<br />
|-<br />
<br />
| St. Bees <br />
|<br />
|<br />
|O<br />
|C-A<br />
|-<br />
|}<br />
</br><br />
<br />
<br />
'''''Sabellaria spinulosa'''''<br />
[[Image:Changing occurence.jpg|thumb|right|300px|Figure 6: Changing occurrences of ''S. spinulosa'' reefs in the Wadden Sea (Wadden Sea Secretariat, 2005). Figure adapted from OSPAR 2010 <ref name= "OSPAR"/>.]]<br />
<br />
Subtidal ''S. spinulosa'' reefs have been reported to have been lost in at least five areas of the northeast Atlantic (Jones ''et al.'', 2000<ref name= "Jones"/>). During the 1920s large reefs of ''S. spinulosa'' were common in the German Wadden Sea (Hagmeier and Kändler, 1927<ref>HAGMEIER A., KANDLER R., 1927. Neue Untersuchungen im nordfriesischen Wattenmeer und auf den fiskalischen Austernbanken.-Wiss. ''Meeresunters''. (Abt. Helgoland). '''16''', 1-90.</ref>) but most have since been lost. Similar records of loss have been recorded from the Lister Ley (Island of Sylt) and the Norderau area (Riesen and Reise, 1982<ref>RIESEN W., REISE K., 1982. Macrobenthos of the subtidal Wadden Sea: Revisited after 55 years, ''Helgolander Meeresuntersuchungen''. '''35''', 409‐423.</ref>; Reise and Schubert, 1987<ref>REISE K., SCHUBERT A., 1987. Macrobenthic turnover in the subtidal Wadden Sea: The Norderaue revisited after 60 years. ''Helgolander Meeresuntersuchungen''. '''41''', 69-82.</ref>). Only three living reefs were found during surveys in the early 1990s compared to 24 during the 19th century (Figure 6). In the late 1990s, samples taken from the subtidal reefs in the German Wadden Sea consisted largely of compact lumps of empty tubes. In 2000, one of these reefs had diminished drastically in extent with the remainder in poor condition although dredge samples were occupied by many tiny tubes with living worms inside. A third reef which had previously extended over ~18 hectares could not be<br />
located during repeat surveys in 2002. In the UK there are reports of reefs being lost in Morecambe Bay (Taylor and Parker, 1993<ref>TAYLOR P.M., PARKER J.G., 1993. An Environmental Appraisal: The Coast of North Wales and North West England, Hamilton Oil Company Ltd, 80 pp.</ref>), the Wash and the Thames (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp Pandalus montagui, in the estuary of the River Crouch, England. ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>). In the western North Sea report comparing records from 1986 and 2000 suggest an increase in distribution and densities in the western North Sea (Rees, 2007<ref>REES, H.L.; EGGLETON, J.D.; RACHOR, E.; VANDEN BERGHE, E. (Ed.) (2007).Structure and dynamics of the North Sea benthos. ''ICES Cooperative Research Report'', 288. ICES: Copenhagen. ISBN 87-7482-058-3. III, 258 + annexes pp. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114857 www.vliz.be/imis]</ref>).<br />
<br />
<br />
<br />
'''''Modiolus modiolus'''''<br />
<br />
Only a few beds are known have been surveyed over long enough time spans for evidence of change to be apparent. In the Irish Sea, south of the Isle of Man, an extensive bed was almost completely lost due to scallop [[dredging]] (Veale ''et al.'', 2000<ref>VEALE L.O., HILL A.S., HAWKINS S.J., BRAND A.R., 2000. Effects of long-term physical disturbances by commercial scallop fishing on subtidal epifaunal assemblages and habitats. ''Marine Biology.'' '''137''', 325-337.</ref>). For similar reasons, beds in Strangford Lough (Northern Ireland) also showed severe declines (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151-1164.</ref>). Recently, beds in North Anglesey (Wales) have been destroyed by fishing activity (Holt, 2008<ref>HOLT 2008, ''Countryside Council for Wales'', pers. comm.</ref>, Countryside Council for Wales, pers. comm.). By contrast, in an Icelandic bay ''Modiolus modiolus'' was still the dominant by‐catch species in scallop dredges 30 years after scallop dredging began (Garcia and Ragnarsson, 2007<ref>GARCIA, E. G., & RAGNARSSON, S. A. 2007. Impact of scallop dredging on macrobenthic communities in Breidafjordur, West Iceland. In: GARCIA, E. G., RAGNARSSON, S.A,, STEINGRIMSSON S. A, NAEVESTADD., HARALDSON H. P., FOSSA J. H., TENDAL, O. S,, & ERIKSSON H. (eds) Bottom Trawling and Scallop Dredging in the Arctic: Impacts of fishing on non‐target species, vulnerable habitats and cultural heritage. Nordic Council of Ministers, Copenhagen, Chapter 2.2.</ref>). In Sullom Voe (Shetland) a bed coincident with a pipeline showed signs of recovery, with some re‐colonisation of disturbed sediment after a few years (Mair ''et al.'' 2000<ref>MAIR J. M., MOORE C. G., KINGSTON P. F. & HARRIES D. B., 2000. A review of the status, ecology and conservation of horse mussel ''Modiolus modiolus'' beds in Scotland. Scottish Natural Heritage, Edinburgh (Commissioned Report F99PA08).</ref>). On the legs of an oil platform in the North Sea a substantial [[population]] was present 10 years after installation, but in this situation the young mussels would have been free of much predation (Anwar ''et al.'' 1990<ref>ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel ''Modiolus modiolus''. ''Journal of the Marine Biological Association of the United Kingdom.'' '''70''', 441‐457.</ref>). As a species it appears to have declined in the North Sea. Comparing occurrences by [[International_Council_for_the_Exploration_of_the_Sea_(ICES)| ICES]] Rectangles Callaway ''et al.'' (2007)<ref>CALLAWAY R., ENGELHARD G. H., DANN J, COTTER J., & RUMHOR H., 2007. A century of North Sea epibenthos and trawling comparisons between 1902‐1912, 1982-1895 and 2000. ''Marine Ecology Progress Series.'' '''346''', 27-43.</ref> showed that the species had been found in 11 rectangles in the 1982‐85 period, but comparable international surveys in 2000 found it in only 1 rectangle.<br />
<br />
<br />
'''''Mytilus edulis'''''<br />
<br />
Surveys covering the whole littoral of Niedersachsen, in Germany, revealed a decrease in the extent of ''M. edulis'' (5000 hectares in the late 1950s, 2700 ha in 1989/91, 1300 ha in 1994 to 170 ha in 1996). Mussel beds in the Ameland region have also disappeared after intensive fishing in the region (Dankers 1993<ref>DANKERS N., 1993. Integrated estuarine management-obtaining a sustainable yield of bivalve resources while maintaining environmental quality. In: DAME R. R. (ed) Bivalve filter feeders in estuarine and ecosystem processes. ''Springer'', Berlin, 479-511. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145584 www.vliz.be/imis]</ref>). In the Netherlands, Higler ''et al.'' (1998<ref>HIGLER B., DANKERS N., SMAAL A.,DE JONGE V.N., 1998. Evaluatie van de ecologische effecten van het reguleren van schlpdievisserij in Waddenzee en Delta op bodemorganismen en vogels. In: VAN DIJK J.J. and R. HEILING (eds.) Structuurnota Zee- en Kustvisserij, van de maatregelen in de kustvisserij gedurende de eerste fase (1993–1997). Appendix 5, pp. 17.</ref>) observed a serious decline in the populations of mussels between 1988 and 1990, mainly caused by fisheries. The extent of mussel beds decreased from the 1970s to the 1990s. In Denmark, intensive fisheries during 1984 to 1987 almost led to a complete disappearance of the mussel population (Kristensen, 1995<ref>KRISTENSEN P.S., 1995. Aerial surveys, biomass estimates, and elimination of the mussel population (''Mytilus edulis'' L.), in the Danish Wadden Sea, 1991±1994. ICES C.M. 1995/K:44, 22 pp. Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=125450 www.vliz.be/imis]</ref>).</br><br />
<br />
<br />
==See also==<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Natural_barriers#Biogenic_reefs |Natural barriers_ Biogenic reefs]]<br />
<br />
[[Dynamics%2C_threats_and_management_of_biogenic_reefs |Dynamics, threats and management of biogenic reefs action]]<br />
<br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Marine habitats and ecosystems]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=8391<br />
|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_salt_marshes&diff=50221Dynamics, threats and management of salt marshes2012-07-24T13:46:08Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
<br />
Coastal areas, like [[estuaries]], are high energetic environments where organisms are exposed to hydrodynamic forces from waves and tidal [[currents]]. Ecosystem engineering species (Jones ''et al.'', 1997) play an important role in shaping the [[intertidal]] landscape (Temmerman ''et al.'', 2007<ref name= "Temmerman">TEMMERMAN, S.; BOUMA, T.J.; VAN DE KOPPEL, J.; VAN DER WAL, D.; DE VRIES, M.B.; HERMAN, P.M.J.(2007). Vegetation causes channel erosion in a tidal landscape. ''Geology''. '''35(7)''', 631-634. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114118 www.vliz.be/imis]</ref>; Weerman ''et al.'', 2010). Coastal vegetation, like [[salt marsh]] vegetation, are ecosystem engineers in that they can strongly attenuate hydrodynamic energy from tidal current and [[waves]] (Bouma ''et al.'', 2005<ref name= "Bouma05">BOUMAT.J.,DE VRIES M.B., LOW E., PERALTA G., TNCZOSI.C.,VANDEKOPPELJ., HERMAN P. M. J., 2005. Trade‐offs Related to Ecosystem Engineering: A Case Study on Stiffness of Emerging Macrophytes. ''Ecology''. '''86''', 2187‐2199.</ref>, 2007<ref name= "Bouam07">BOUMA, T.J.; VAN DUREN, L.A.; TEMMERMAN, S.; CLAVERIE, T.; BLANCO-GARCIA, A.; YSEBAERT, T.J.; HERMAN, P.M.J. (2007). Spatial flow and sedimentation patterns within patches of epibenthic structures. ''Cont. Shelf Res.''. '''27(8)''': 1020-1045. dx.doi.org/10.1016/j.csr.2005.12.019<br />
Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=114437 www.vliz.be/imis]</ref>, 2010). This has a positive effect on sediment accretion rates, and hence results in increased sediment elevation. In turn, increased sediment elevation stimulates plant growth because the inundation duration for the vegetation is shortened. This results in positive feedbacks between plant growth and sediment accretion. Implications of this feedback can be observed in the field in the form of dome shaped hummocks of cord‐grass (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina spp.]''). They can be found on the [[Tidal flats from space|mud flats]] seaward of the salt marsh edge (Figure 1), where the salt marsh is developing.<br />
<br />
Feedbacks between hydrodynamic forces, sediment accretion and vegetation are key processes in shaping salt marshes (Temmerman ''et al.'', 2007<ref name= "Temmerman"/>; van Wesenbeeck ''et al.'', 2008). Locally the canopy of a vegetation stand can attenuate currents and waves which result in a net [[sedimentation]]. However, the same canopy also obstructs the flow, thereby diverting it and increasing flow velocities in the areas adjacent to the canopy because of conservation of mass and energy (Bouma ''et al.'', 2009). This biomechanical stress diversion can result in negative feedbacks on vegetation settlement and growth at some distance from the canopy (van Wesenbeeck ''et al.'', 2008). However, the outcome of these feedbacks may be dependent on the local context, seeing as these kinds of feedbacks are density‐dependent (Bouma ''et al.'', 2009). In other words, the strength of these negative feedbacks may vary with vegetation age, composition, or even the sediment type it is growing in (van Hulzen ''et al.'', 2006<ref name= "van Hulzen">VAN HULZEN J.,VAN SOELEN J.,HERMAN P.M.J., BOUMA T.J., 2006.The significance of spatial andtemporal patterns of algal mat deposition in structuring salt marsh vegetation. ''J Veget Sci.''. '''17''', 291‐298.</ref>). Overall these feedbacks cause complex patterns of gullies and hummocks until eventually a mature marsh arises, dissected by a complex drainage system (Kirwan and Murray, 2007; Temmerman ''et al.'', 2007<ref name= "Temmerman"/>).<br />
<br />
Many marshes are characterized by a cyclic nature, where marsh formation is followed by destruction (Figure 2). After a period of lateral extension, large scale lateral erosion of salt marshes can set in when the marsh edge becomes disturbed, a phenomenon often referred to as cliff erosion (see Figure 1.a, Figure 2.B.b; Allen, 2000<ref name= "Allen">ALLEN J.R.L., 2000. Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe. ''Quaternary Science Reviews''. '''19''', 1155-1231.</ref>; Adam 2002<ref name= "Adam">ADAM P., 2002. Salt marshes in a time of change. ''Environmental Conservation''. '''29''', 39‐61</ref>). For example, a disturbance from a [[storm surge]] can initialize this erosion process by forming a steep slope. At the disturbed edge, sediment is more vulnerable to wave action and currents. So once a cliff starts to erode, this process will not easily be stopped. Thus the steep slope remains particularly vulnerable for waves and currents until it is protected by new marsh vegetation emerging in front of the cliff. The initiation of cliff erosion is intrinsic to natural temporal salt marsh dynamics (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel">VAN DE KOPPEL J.,VAN DER WAL D., BAKKER J.P.,HERMAN P.M.J., 2005. Self‐Organization and Vegetation Collapse in Salt Marsh Ecosystems. ''The American Naturalist''. '''165''', E1-12.</ref>). However, human activities can contribute significantly to the severity of the cliff erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>). For example, shipping traffic and [[dredging]] activities can increase exposure to currents and waves, thereby increasing the pace at which lateral erosion proceeds. Moreover, human induced activities may also take away the space for natural marsh recovery in front of the eroding cliff. The latter would result in the permanent loss of a marsh.<br />
<br />
Loss of salt marsh habitat due to lateral erosion is a major problem across the world, especially in those locations where the marsh does not seem to recover. For example, the marshes in the [[Biodiversity_and_conservation%2C_and_role_of_marine_protected_areas#Venice_Lagoon |Venice Lagoon]] (Italy) laterally erode with 1.2‐2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day">DAY J.W., SCARTON F., RISMONDO A., ARET D., 1998. Rapid Deterioration of a Salt Marsh in Venice Lagoon, Italy. ''Journal of Coastal Research''. '''14''', 583‐590.</ref>) .The estuaries of South‐East England lose about 4,000 m² <math>yr^{-1}</math> of tidal marsh area due to erosion at the seaward edges and channel widening of creeks dissecting the marsh (Hughes and Paramor, 2004<ref name= "Hughes">HUGHES R.G., PARAMOR O.A.L., 2004. On the loss of saltmarshes in south‐east England: methods for their restoration. ''Journal of Applied Ecology''. '''41''', 440‐448.</ref>). However, the main drivers of salt marsh erosion are still subject of debate (Wolters ''et al.'', 2005<ref name= "Wolters">WOLTERS M., BAKKER J.P., BERTNESS M.D., JEFFERIES R.L., MÖLLER I., 2005. Saltmarsh erosion and restoration in south-east England: squeezing the evidence requires realignment. ''Journal of Applied Ecology''. '''42''', 844‐851. </ref>). Generally, it is believed that human activities are responsible for increasing erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Pollution, shipping and dredging are some of the proposed [[anthropogenic]] causes. In addition, climate change and [[sea level rise]] receivemuch attention as a cause of salt marsh disappearance. In addition to these extrinsic forcing factors, intrinsic biological processes are also proposed (Allen, 2000<ref name= "Allen"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). For example, vegetation‐sediment feedbacks (Allen, 2000<ref name= "Allen"/>) and sediment destabilization by bioturbation and herbivory by worms (Hughes and Paramor, 2004<ref name= "Hughes"/>; van der Wal and Pye, 2004<ref name= "van der wal">VAN DER WAL D., PYE K., 2004. Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK). ''Geomorphology''. '''61''', 373‐391.</ref>) and geese (Dionne, 1985<ref>DIONNE, J.-C., 1985. Tidal marsh erosion by Geese, St. Lawrence estuary, Québec. ''Géographie physique et Quaternaire''. '''39''', 99‐105.</ref>) can also result in erosion of salt marshes. A fundamental understanding of the mechanisms that control cliff initiation and salt marsh re‐establishment in front of a cliff is needed in order to protect and manage these highly dynamic salt marsh ecosystems.<br />
</br><br />
</br><br />
<br />
{|style="margin: 1em auto 1em auto;"<br />
|[[Image: Eroding cliff.JPG|thumb|left|300px| Figure 1: (A) Eroding cliff. (B) Patchy vegetation at pioneer zone of mudflat and saltmarsh interface. A dome-shaped patch is seen in front. (C) Salt marsh with eroding cliff separating the low marsh and pioneer zone. Pioneer vegetation (''Spartina'') has colonized the area below the eroding cliff (see also fig. 1.A). Photographs by J. van Belzen.]]<br />
|[[Image:overview of saltmarsh.JPG|thumb|none|300px| Figure 2: (A) Overview of saltmarsh by aerial photograph (RWS), comparable to situation (B.b). Cross-shoreprofile of salt‐marsh dynamics of conceptual ecomorphological model, which mimics the development of the marsh in (A). Here, (―) is the initial bare mud--‐flat profile, (―) is vegetated marsh profile at beginning, and (---) is the final profile. First, (a) saltmarsh generation due to the positive feedback between vegetation and sedimentation.Second, (b) cliff erosion of old marsh and subsequent growth at the pioneer zone (after van de Koppel, ''et al.'', 2005<ref name= "Van de Koppel"/>).]]<br />
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==VULNERABILITY & THREATS TO SALT MASRHES==<br />
===Short-term effects of flooding and storms===<br />
====SHORT-TERM FLOODING: Vulnerability of marshes to saltwater flooding====<br />
<br />
The salt‐marsh community is well adapted to salinity due to regular tidal exposure to seawater. The vast majority of salt-marshes are well drained and therefore at less risk to the endured flooding. In comparison, the community of grazing-marshes is adapted to very dilute seawater and the habitat drainage is often slow. The potential impact of saltwater flooding is therefore more severe for [[Coastal_grazing_marsh| grazing marshes]] than for salt marshes. Much of the evidence regarding the effect of seawater on coastal vegetation therefore relates to oligohaline/grazing marshes.<br />
</br><br />
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<br />
====SHORT-TERM FLOODING: Effect of flooding by saline water on salt marshes ====<br />
<br />
A flooding event that originates from increased freshwater discharge, for instance due to heavy rainfall or ice melt in a catchment area, will result in a fresh‐water pulse through downstream marshes. Unless freshwater flooding lingers for extensive periods, the impact on the vegetation of salt-and grazing- marshes will be short lived (Flynn ''et al.'', 1995<ref name= "Flynn">FLYNN, K.M.; MCKEE, .KL.; MENDELSSOHN, I.A, 1995.RECOVERY OF FRESH-WATER MARSH VEGETATION AFTER A SALTWATER INTRUSION EVENT.'' OECOLOGIA''. '''103(1)''', 63-72 DOI:10.1007/BF00328426.</ref>; Grace and Ford, 1996<ref name= "Grace">GRACE J.B., FORD M.A., 1996. The potential impact of herbivores on the susceptibility of the marsh plant ''Sagittaria lancifolia'' to saltwater intrusion in coastal wetlands. ''Estuaries''. '''19''', 13–20.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard">HOWARD R.J., MENDELSSOHN I.A., 2000. Structure and composition of oligohaline marsh plant communities exposed to salinity pulses. ''Aquat Bot''. '''68''', 143–164.</ref>). The [[Halophytic_plants|‘halophytic’]] (salt-tolerant) species that dominate salt-and grazing-marsh communities will not be harmed by short‐term fresh water exposure. However, their physiological and biochemical adaptations to cope with salinity stress make them poorly competitive under fresh water conditions (Crain ''et al., 2004''<ref name= "Crain">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549.DOI: 10.1890/03-0745 </ref>). Their halophytic traits enable them to colonise saline environments (Pennings and Callaway, 1992<ref name= "Pennings">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549. DOI: 10.1890/03-0745 </ref>). Salinity exposure in the salt marsh, and consequently the inherent salt tolerance of the inhabitant community, does not necessarily decline linearly with shore level. Summer evaporation of seawater pools can leave concentrated deposits of salt on the high marsh where the habitat is infrequently flushed, leading to high levels of sediment salinity that exclude less halophytic species (Watson and Burne, 2009). Paradoxically, increased frequency of seawater flushing by storms might dilute the accrued sediment salinity of such high marsh environments and alter the zonation of species. For instance, increased tidal flooding of an elevated marsh plain can cause the normally very halophytic high marsh species to be replaced by salt‐intolerant lower shore species (Watson and Burne, 2009).<br />
<br />
The severity of impact of salt water flowing is likely to depend on the natural salinity occurring at a specific location. Relatively brackish-marshes, dominated by halophytic plants, will see less changes to community composition than fresh water dominated grazing marshes and coastal flood plains (Brown ''et al.'', 1994). Increased flooding by salt water is most likely to have the greatest effect on the fresh‐water adapted members of the marsh vegetation (Crain ''et al.'', 2004<ref name= "Crain"/>), which increases in dominance in the transitional and grazing‐marsh above the tidal marks. Stormy conditions that result in a temporary increase in sea level and which bring in salt water pulses to coastal marsh systems therefore should have a greater effect on the grazing‐marsh community than on the salt marsh community. For example, seawater flooding of a diked grazing-marsh, following a dike breaching, prevented most of the fresh water vegetation from developing in the following spring (Klein and Bateman, 1998<ref name= "Klein">KLEIN R.J.T., BATEMAN I.J., 1998. The recreational value of Cley marshes nature reserve: An argument against managed Retreat? ''Water and Environment Journal''. '''12''', 280-285. </ref>). Vegetation cover, species richness, recovery and re-establishment of an oligohaline marsh decreased during one month of experimental exposures to increased salinity (from 0.5‐5.0 salinity up to 12) (Howard and Mendelssohn, 2000<ref name= "Howard"/>). In the longer term, the space left by dead vegetation is likely to be colonised by more salinity tolerant species, and thus grazing-marsh communities might come to resemble those of salt marshes (Doody, 1982<ref name= "Doody">DOODY J.P., 1982. Sea defence and nature conservation: threat or opportunity. ''Aquat Conserv Mar Freshw Ecosyst'', '''2''', 275-283.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard"/>).<br />
<br />
Many coastal marsh plants are able to recover temporary increases in salinity (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Grace and Ford, 1996<ref name= "Grace"/>; Howard and Mendelssohn, 2000<ref name= "Howard"/>). However, the potential for lasting changes to communities increases with the duration of flooding (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Howard and Mendelssohn 2000<ref name= "Howard"/>). Elevated salinity (from natural, 0.5‐5 to 15) slowed vegetation recovery more in flooded than in drained soils (Flynn ''et al.'', 1995<ref name= "Flynn"/>). The naturally slow drainage of grazing marshes, that follows temporary sea water flood, causes this habitat to remain immersed for longer periods than salt marshes. Grazing marshes are therefore at greater risk to the endured flooding. However, there are indications that these marshes are relatively resilient to exposure; if the water is brackish enough, it may require months of immersion before significant impacts to vegetation cover occurs (e.g. Howard and Mendelssohn, 2000<ref name= "Howard"/>). Brewer and Grace (1990)<ref>BREWER J.S., GRACE J.B., 1990. Plant community structure in an oligohaline tidal marsh. ''Vegetatio''. '''90''', 93–107.</ref> hypothesized that occasional storm‐generated pulses of salt water moving into an oligohaline marsh would generate short-lived salinity gradients that, along with biotic interactions, would regulate species distributions over longer terms. Sharpe and Balwin (2009)<ref name= "Sharpe">SHARPE P. J., BALWIN A.H., 2009. Patterns of Wetland Plant Species Richness Across Estuarine Gradients of Chesapeake Bay. ''Wetlands''. '''29''', 225-235.</ref> proposed that an unexpected peak in vegetation species richness in the transitional marsh arose because pulsed variation in salinity (0‐5) prevented domination by fresh water or salt water species. Thus, pulsed salinity exposure might not necessarily diminish vegetation diversity. Nevertheless, increased salt water flooding of grazing marshes is likely to drive the succession towards more salt-tolerant vegetation, and increase the resemblance with salt marsh assemblages. Note that the empirical evidence for the rate of this transition is lacking (Nicholls and Wilson, 2001<ref name= "Nicholls">NICHOLLS R.J., WILSON T., 2001. Chapter five. Integrated impacts on coastal areas and river flooding. In: Holman I.P., Loveland P.J. (Eds), Regional Climate Change Impact and Response Studies in East Anglia and North West England (RegIS). Final Report of MAFF project no. CC0337. (downloadable at [http://www.ukcip.org.uk www.ukcip.org.uk]).</ref>). The consequence of increased coastal flooding might therefore be a gradual loss of grazing-marsh communities, in exchange for gain in area cover of salt marsh communities (Doody, 1982<ref name= "Doody"/>; Klein and Bateman, 1998<ref name= "Klein"/>; Nicholls and Wilson, 2001<ref name= "Nicholls"/>). <br />
</br><br />
<br />
<br />
====SHORT-TERM FLOODING: Interactions of salinity with other disturbances ====<br />
<br />
It is important to caution against a general interpretation that seawater flooding is a minimal risk to coastal marshes in general. The severity of seawater influence on grazing‐marshes might depend much on whether the salinity is paralleled with other plant stressors and disturbances. Sharpe and Balwin (2009)<ref name= "Sharpe"/> sampled plant diversity in a marsh in the United States, across a fresh (salinity 0.5) to mesohaline (5-18) salinity gradient. In an undisturbed marsh, richness in transition zone oligohaline marshes was as high as or higher than in tidal fresh water-marshesIn an anthropogenically disturbed estuary, however, plant species richness declined linearly with an increase in salinity. Experimental flooding by brackish (6‐14) water had a greater effect on grazing‐marsh community structure and [[biomass]] when the vegetation was also disturbed by leaf clipping (Baldwin and Mendelssohn, 1998) or grazing (Gough and Grace, 1998). In comparison, flooding did not affect species richness in the absence of such additional disturbances (Baldwin and Mendelssohn, 1998). If the salinity and water regimes are permanently altered and/or the vegetation is destroyed by a combination of factors, the substrate might eventually subside. Substrate [[Natural_causes_of_coastal_erosion#Subsidence |subsidence]] and associated increased water depth might prevent seed dispersal and germination of more flooding tolerant species, and thus hamper system recovery (McKee and Mendelssohn, 1989<ref name= "Mckee en M">MCKEE K.L.; MENDELSSOHN I.A.,1989. Response of a fresh-water marsh plant community to increased salinity and increased water level. ''AQUATIC BOTANY''. '''34(4)''', 301-316. DOI: 10.1016/0304-3770(89)90074-0.</ref>).It is not known beyond which threshold the frequency of flooding will have permanent effects.<br />
</br><br />
<br />
<br />
====SHORT-TERM: Vulnerability of marshes to storm damage====<br />
<br />
As mentioned above, flooding can induce some disturbances to the vegetation composition of salt marshes. However, the threat storms impose on salt marshes is more likely to result from storm-associated damage than from flooding. Wind-induced waves can destabilize sediments, initiate and propagate lateral cliff erosion, tear of plant material, as well as deposits of wrack and debris in marshes. The [[vulnerability]] of salt marshes is largely related to the effects of waves on sediment stability and on lateral erosion. The evidence we present for the effects of storm associated erosion mostly originates from salt marshes seeing as the literature on grazing-marsh damage from salt water erosion is scarce. Severe salt marsh erosion will undoubtedly lead to an increased risk of sea water flooding and storm-associated damage for adjoined grazing‐marshes, and might eventually drive a transition of grazing‐marsh communities into salt marsh habitats.<br />
</br><br />
<br />
<br />
====SHORT-TERM STORM: Sediment destabilization and lateral erosion of salt marshes====<br />
<br />
Storm events can induce sediment stabilization and lateral erosion, which can have an important impact on the dynamics and functioning of salt marshes. Although lateral erosion is an intrinsic process for salt marshes and part of the natural cyclic behaviour, it generally gets initiated by a storm (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Such cyclic behaviour requires sufficient space for marshes to migrate landward. This space is nowadays being diminished due to anthropogenic land use. Hence, the lateral erosion of salt marshes has become a global threat, as it is unclear under which conditions an eroding marsh can re‐establish in the limited available space. For example, the marshes in the Venice Lagoon (Italy) erode 1.2-2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day"/>) and estuaries of South-East England lose ~4,000 m² of tidal marsh per annum from erosion at the seaward edges and widening of creeks within the marsh (Hughes and Paramor, 2004<ref name= "Hughes"/>). In these locations, large areas of marsh are lost due to cliff erosion with little or no recovery of the vegetation. <br />
<br />
It is clear that storms contribute significantly to the loss by lateral erosion. However, the main driving factors initiating this erosion are still not clear (Wolters ''et al.'', 2005<ref name= "Wolters"/>). Human activities can be, in part, responsible for increasing erosion rates through [[pollutant]]-driven diminishing of vegetation cover and/or by enhancing hydrodynamic energy reaching the marsh via ship waves and channel dredging (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Thus, there is a strong need for a fundamental understanding of the cyclic functioning of salt marsh ecosystems in order to understand when disturbances by storms will start a natural cycle of rejuvenation versus when they cause the irreversible loss of a marsh and thus would benefit from protective measures. <br />
<br />
Vulnerability of the saltmarsh to the initiation of cliff erosion will largely depend on the age of the marsh. Cliff erosion is hypothesized to be an inevitable and intrinsic consequence of the ecomorphological dynamics of saltmarshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). That is, the capture of sediment by the vegetation leads to vertical salt marsh growth, which in the long term makes the salt marsh susceptible to lateral erosion (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). Both conceptual modelling and empirical evidence showed that a positive feedback between vegetation growth and sediment capture generates an increasingly steeper bank at the seaward edge of the marsh (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). As a consequence, salt‐marsh edges become more vulnerable to disturbance as they mature (see Figure 1.B). This means that in the end, relatively small disturbances like from minor storm events or ship waves may induce the erosion. Data on sedimentation in salt-marshes, obtained from sediment core transects and spatiotemporal analysis of aerial photographs, support this conceptual model (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal">VAN DER WAL D., WIELEMAKER-VANDENDOOL A., HERMANP.M.J., 2008. Spatial patterns, rates and mechanisms of saltmarsh cycles (Westerschelde, The Netherlands). ''Estuarine, Coastal and Shelf Science''. '''76''', 357‐368. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=143078 www.vliz.be/imis].</ref>), suggesting that, in a wide range of circumstances, lateral retreat due to cliff erosion will happen sooner or later. <br />
<br />
[[Resilience]] of the marsh edge to erosion will depend on the interplay between vegetation composition and sediment dynamics. For instance, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina]'' plants reduce cliff erosion more than ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=232101 Limonium]'' plants do due to differences in their root system. As a consequence, a ''Spartina'' dominated marsh edge is likely less vulnerable to storm events (van Eerdt, 1985). However, consequences of plant community on the vulnerability and resilience of the marsh can be more complex. The above ground plant traits can have other effects on the vegetation-sediment interaction. For example, stiffness and density of the plant may affect sedimentation rates (Bouma ''et al.'', 2005<ref name= "Bouma05"/>, 2009, 2010). The overall effect of above and below plant traits on salt‐marsh resilience/vulnerability remains largely unknown and subject to ongoing research. <br />
<br />
Alongside cliff erosion, re‐growth of pioneer vegetation on the cleared mudflat in front of the saltmarsh cliff ideally occurs, thereby rejuvenating the mature marsh (see Figure.1.B; van de Koppel, ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>). This pioneer vegetation determines the conditions for lateral retreat and gradually slows down erosion of the salt-marsh edge. <br />
<br />
The establishment of pioneer vegetation is therefore of vital importance for the development and recovery of salt marshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>; Callaghan ''et al.'', 2010<ref name= "callaghan">CALLAGHAN, D.P.; BOUMA, T.J.; KLAASSEN, P.; VAN DER WAL, D.; STIVE, M.J.F.; HERMAN, P.M.J., 2010. Hydrodynamic forcing on salt-marsh development: Distinguishing the relative importance of waves and tidal flows Est., ''Coast. and Shelf Sci.''. '''89(1)''', 73-88. dx.doi.org/10.1016/j.ecss.2010.05.013. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=206900 www.vliz.be/imis].</ref>). This emphasizes the importance of initial conditions for the establishment and growth of vegetation, and the physical conditions that may constrain these intrinsic processes for salt marsh development (van der Wal ''et al.'', 2008<ref name= "VdWal"/>). However, the factors limiting seedling establishment remain poorly understood (Bouma ''et al.'', 2009). We hypothesize that sediment destabilization plays a critical role in the ability for pioneer establishment on a mudflat and, therefore, in the ability of the salt marsh to recover from lateral cliff erosion (Balke ''et al.'', submitted; Bouma ''et al.'', submitted; van Belzen ''et al.'', in prep a; Infantes ''et al.'', submitted). <br />
</br><br />
<br />
<br />
====SHORT-TERM STORM: sediment and wrack deposits on salt marshes====<br />
<br />
Depositions of wrack, debris or large amounts of sediment, associated with extreme flooding events, can have significant effects on salt marsh vegetation. Wrack depositions may smother less hardy vegetation, leaving bare patches and opportunity for new colonization by neighbouring species, or from dispersed seeds (Bertness and Ellison, 1987<ref>BERTNESS M.D., ELLISON A.M., 1987. Determination of pattern in a New England salt marsh plant community. ''Ecol Monogr''. '''57''', 129‐14.</ref>; Tolley and Christian, 1999<ref name= "Tolley">TOLLEY P.M.; CHRISTIAN R.R., 1999. Effects of increased inundation and wrack deposition on a high salt marsh plant community. ''ESTUARIES''. '''22(4)''', 944-954.DOI: 10.2307/1353074.</ref>). Large algal mats can have residence times of 3‐4 months (Valiela and Rietsma, 1995<ref name= "Valiella">VALIELA I.; RIETSMA C.S.,1995. DISTURBANCE OF SALT-MARSH VEGETATION BY WRACK MATS IN GREAT-SIPPEWISSETT-MARSH. ''OECOLOGIA''. '''102(1)''', 106-112. </ref>). While wrack depositions may not be as significant in cover (Valiela and Rietsma, 1995<ref name= "Valiella"/>), small-scale alteration in species cover by algal wrack depositions does have the potential for wider effects on community diversity if the same spots are regularly covered by seaweed (van Hulzen ''et al.'', 2006<ref name= "van Hulzen"/>). The deposition of sediments following storm flooding may be significant. Experimental flooding and sedimentation of seedbanks of an oligohaline marsh community showed that an addition of 2 cm of sediment decreased plant density and germination of seedlings, suggesting that an increase in sedimentation and relative sea level may reduce plant biodiversity (Peterson and Baldwin, 2004<ref>PETERSON J.E., BALDWIN A.H., 2004. Seedling emergence from seed banks of tidal freshwater wetlands: response to inundation and sedimentation. ''Aquat Bot''. '''78,''' 243–254. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=59970 www.vliz.be/imis].</ref>]). The deposition of sediments might be positive for subducting and nutrient starved marshes. For example, within a year after 3-8 cm of sediment deposited by Hurricane Katrina, the vegetation of a high marsh had fully recovered and below‐ground root growth had increased 10‐fold (McKee and Cherry, 2009<ref name= "Cherry">MCKEE K.L., CHERRY J.A., 2009. Hurricane Katrina sediment slowed elevation loss in subsiding brackish marshes of the Mississippi river delta. ''Wetlands''. '''29''', 2-15.</ref>).<br />
<br />
While single factors may have limited effects on marshes, a collective of concurrent stressors is likely to generate significant impacts on marsh communities. The deposition of wrack and sediments is often concurrent with other habitat stressors that might jointly influence marsh vegetation cover. Thus, while Tolley and Christian (1999)<ref name= "Tolley"/> found little effect of sea water flooding on vegetation biomass, the simultaneous deposition of algal wrack greatly repressed plant cover and biomass, in some species irreversibly so.<br />
</br><br />
<br />
<br />
===Long-term effects due to climate change and sea level rise===<br />
<br />
[[Coastal squeeze]], due to sea level rise, and erosion are primary threats to salt marshes across Europe. They can result in reduced coastal defence value and in an increased risk of flooding. Although sea level rise may pose serious threats to the survival of salt marshes, there is growing evidence that as long as sediment supply is sufficient, the vegetation-sedimentation feedback of marshes enables marshes to accrete vertically at the rate of the rising sea-level (Kirwan and Temmerman, 2009<ref name= "KenT">KIRWAN M., TEMMERMAN S., 2009. Coastal marsh response to historical and future sea-level acceleration. ''Quaternary Science Reviews''. '''28''', 1801-1808.</ref>). However, if the suspended matter load is reduced by climate change or by significant human alteration in a catchment area, vegetation- sedimentation feedbacks can become limited, affecting the potential of marshes to accrete (Kirwan and Temmerman, 2009<ref name= "KenT"/>). As explained in the previous sections, lateral marsh erosion can become a serious threat to salt marshes over time if seedling establishment in front of the marsh is not possible so that re- growth of the marsh is prevented. Many aspects that affect the cyclic dynamics of marshes are still not well understood. Important in maintaining the vegetation-sedimentation feedback is that the sedimentary conditions remain more or less the same.<br />
<br />
Several managerial aspects are likely to compromise the capacity for marshes to persist and to protect the coast. Reduction in area by coastal squeeze will reduce the wave attenuation capacity, as the efficiency of energy reduction is strongly dependent on the depth of the marsh (Möller, 2006<ref name= "Moller">MÖLLER I., 2006. Quantifying saltmarsh vegetation and its effect on wave height dissipation: Results from a UK East coast saltmarsh. ''Estuarine Coastal and Shelf Science''. '''69''', 337‐351.</ref>). Whether this might have negative feedback on marsh accretion and accelerate area loss is not known. Effects of grazing might also reduce the vegetation‐sedimentation feedback by reducing vegetation cover and height, thereby hampering the development of salt marshes (Kiehl ''et al.'', 2007<ref name= "Kiehl07">KIEHL K., SCHRÖDER H., STOCK M., 2007. Long‐term vegetation dynamics after land‐use change in Wadden Sea salt marshes. ''Coastline Reports''. '''7''', 17‐24.</ref>). Finally, very little is known about the implications on salt marsh resilience from interactions between different environmental, climatic and managerial variables. Interactions between climate stressors (e.g. desiccation, irradiation), physical forcing (extreme flooding events, increased storminess) and environmental management (eutrophication, grazing, and managed retreat) will be a likely reality for many marshes. This is important because interactive stresses can be synergistic and cause shifts in the stable states of ecosystems, which can compromise the naturally delivered services (Scheffer ''et al.'', 2001<ref>SCHEFFER M., CARPENTER S., FOLEY J.A., FOLKER C., WALKER B., 2001. Catastrophic shifts in ecosystems. ''Nature''. '''413''': 591‐596. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=19763 www.vliz.be/imis].</ref>; Scheffer ''et al.'', 2009<ref>SCHEFFER M., BASCOMPTE J.,BROCK W. A., BROVKIN V., CARPENTER S., DAKOS V.,HELD H., VANNESE.H., RIETKERK M., SUGIHARA G., 2009. Early-warning signals for critical transitions. ''Nature''. '''461''', 53‐59. </ref>). Our evaluation of the resilience of salt marshes to disturbance, including climate change, might for the time being still be somewhat naïve and based on limited current research. <br />
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<br />
<br />
====CASE STUDY: FORECASTING THE EFFECTS OF SEA‐LEVEL RISE====<br />
[[Image: Chongming Dongtan.JPG|thumb|right|350px|Figure 3: Impact of sea-level rise on tidal flat and tidal marsh complex by 2050 (a and b) and 2100 (c and d) year at Chongming Dongtan nature reserve.]]<br />
<br />
Located at the mouth of the Yangtze Estuary, the Chongming Dongtan nature reserve is extremely vulnerable to climate change and especially to an accelerated sea-level rise. We use a variety of data from [[remote sensing]], an in situ global positioning system (GPS), tidal gauges, nautical charts, geographic spatial analysis modelling gand IPCC sea-level rise scenarios to forecast the potential impacts of increased sea level on the coastal wetland habitat of the Chongming Dongtan Nature Reserve (Figure 3). The results indicate that around 40% of the intertidal zone of the nature reserve will be inundated by the year 2100 due to an estimated 0.88 m increase in sea level (Figure 3.c and 3.d). In particular, the ''Scirpus mariqueter'' communities and bare tidal flats are more vulnerable to sea‐level rise. The identification, mapping and statistical summary of environmental impacts of the projected sea-level rise at Chongming Dongtan Nature Reserve represent an important initial step for decision makers concerned with mitigation of the adverse impacts of sea-level rise. In this study, the inundation‐based assessment was developed to inform policymakers, managers and the public about the amount and the spatial distribution of tidal wetland change as a result of sea‐level rise. The results indicate that the zones most vulnerable to sea-level rise at the Chongming Dongtan Nature Reserve is the ''S. Mariqueter'' zone, the bare tidal flat zone and the tidal creeks, which are the most suitable habitats for migratory birds. A ~30% loss of the ''S. Mariqueter'' marsh community by the year 2100 would eliminate a rich invertebrate food source and cause deterioration in the estuarine food web for migrating birds; such a loss could arise from human-induced stressors such as land reclamation, seawall constructions, overfishing and local pollution. As tidal marshes and flats submerge and decline in size and productivity, increased crowding in the remaining areas could lead to reductions in and eventually even exclusion of some local shorebird populations (Tian ''et al.'', 2010<ref>TIAN, B; ZHANG, LQ ; WANG, XR; ZHOU, YX ; ZHANG, W.; 2010. Forecasting the effects of sea-level rise at Chongming Dongtan Nature Reserve in the Yangtze Delta, Shanghai, China. ''ECOLOGICALENGINEERING'', '''36(10)''': 1383-1388.DOI: 10.1016/j.ecoleng.2010.06.016.</ref>). <br />
</br><br />
<br />
<br />
==KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY ==<br />
===Effects of single disturbance events on marsh responses to long-term change===<br />
<br />
Single events, such as violent storms, normally have short-lived effects on the species composition and on the ecological functioning of salt-marshes (Flynn ''et al.'' 1995<ref name= "Flynn"/>, Howard and Mendelssohn, 2000<ref name= "Howard"/>; McKee and Cherry, 2009<ref name= "Cherry"/>), and are thus of less importance compared to long term persistent changes in environmental condition. Long-term processes of coastal squeeze with sea level rise and lateral erosion with increased storminess are considered to be the primary threats to salt- and grazing-marshes across Europe (Nicholls and Wilson, 2001<ref name= "Nicholls"/>. A single storm can push a marsh over the tipping point, shifting it from laterally expanding towards laterally eroding. If erosion persists, and the marsh cannot re-establish in front of the cliff, in time this will result in reduced coastal defence value and an increased risk of flooding of adjacent terrestrial environment (e.g. grazing- marshes) (Klein and Bateman, 2007).<br />
</br><br />
<br />
<br />
==CURRENT MANAGEMENT PRACTICES==<br />
===Making space for water===<br />
<br />
Currently, salt-marshes are managed extensively because of their acknowledged role in coastal protection. Many countries like e.g. the UK, the Netherlands, etc, have developed management schemes in order to make space for water along river flood plains, estuarine and coastal areas (Bakker, ''et al.'', 2005; DEFRA, 2004). This way, river run‐off and occasional high sea water levels can be attenuated by the natural buffer and retention capacity of the landscape. For example, restoring the water storage volume in an estuary can reduce the tidal prism, smoothing the tidal amplitude, which reduces the risk of flooding in up-stream estuarine areas. Salt‐marshes play an important part in this contemporary policy, because creating new marsh‐land both increases tidal water storage in up‐stream estuarine areas and wave attenuation of storm surges along exposed coast lines (Bakker ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>).<br />
</br><br />
<br />
<br />
===Managed retreat/realignment and salt-marsh engineering===<br />
<br />
The current effort to restore marsh systems in Europe and elsewhere represents graphic evidence of the political and managerial value placed on the goods and services provided by this ecosystem. The principle of ‘managed realignment’ and ‘managed retreat’ comes down to allowing salt-marsh areas, that were historically converted to alternative use for anthropogenic purposes (e.g. agricultural land or tourist development), to return to their natural state and area cover (Garbutt, ''et al.'', 2006<ref>GARBUTT, R.A.; READING, C.J.; WOLTERS, M.; GRAY, A.J.; ROTHERY, P., 2006. Monitoring the development of intertidal habitats on former agricultural land after the managed realignment of coastal defences at Tollesbury, Essex, UK. ''MARINE POLLUTION BULLETIN''. '''53(1-4)''', 155-164. DOI: 10.1016/j.marpolbul.2005.09.015.</ref>). This can be done in a number of ways, but typically involves making a breach in the historically erected barrier (seawall, dike) rather than removing the whole structure. This approach reduces the costs involved, as well as the wave action depressing the development of the vegetation. Cost benefit analyses typically show a net advantage of managed realignment over other constructed defence options (Turner, ''et al.'', 2007<ref>TURNER, R.K.; BURGESS, D .; HADLEY, D.; COOMBES, E.; JACKSON, N.; 2007. A cost-benefit appraisal of coastal managed realignment policy. ''GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS''. '''17(3-4)''': 397-407.DOI: 10.1016/j.gloenvcha.2007.05.006.</ref>). Full restoration of natural ecosystem function has met some complications. The substrates and biodiversity of pristine salt marshes is often markedly different from an artificial or restored system, even 100 years after natural processes have been allowed to operate (Hazelden and Boorman, 2001<ref>HAZELDEN J.; BOORMAN L.A.; 2001.Soils and 'managed retreat' in South East England.''SOIL USE AND MANAGEMENT''. '''17(3)''':150-154. DOI: 10.1079/SUM200166.</ref>). The implications of this managed realignment on coastal protection by marshes are not known. The MOSE project of the Venice lagoon is an impressive example of large-scale engineering to create salt‐marsh wetlands, largely for their role in dampening wave action and erosion within the lagoon (MOSE 2010).<br />
</br><br />
<br />
<br />
===Grazing management and coastal protection===<br />
<br />
There is evidence to suggest that grazing management could be of particular importance to the capacity of marshes for protecting the coast, although there has been little quantitative research on this subject (Bakker, ''et al.'', 2005). The vegetation is of key importance to coastal protection by marshes, through consolidation of the soil and by representing a structural hindrance to wash-over waves. Evidently, livestock has large potential for altering the vegetation structure directly through feeding and indirectly by altering the conditions for vegetation growth (Bakker, ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>). Feeding and defecation moderate vegetation structure‐composition and above- and below-ground biomass production. Trampling and hoof holes lead to soil compaction and can cause saltpan formation (Vera, 2000<ref>VERA F.W.M., 2000. Grazing Ecology and Forest History. CABI Publishing, Wallingford, UK.</ref>). The potential of management of grazing regime to influence the salt marsh coastal protection potential is therefore high. Intense grazing modifies zonation patterns and transforms complex communities with woody species into homogenous lawns dominated by short flexible grass (Andresen, ''et al.'', 1990<ref name= "Andersen">ANDRESEN H., BAKKER J.P., BRONGERS M., HEYDEMANN B., IRMLER U., 1990. Long‐term changes of salt-marsh communities by cattle grazing. ''Vegetatio''. '''89''', 137–148.</ref>; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>), with an associated likely reduction in wave attenuation (Möller, 2006<ref name= "Moller"/>) and sedimentation rates (Andresen, ''et al.'', 1990<ref name= "Andersen"/>). Grazing at low intensity increases vegetation patchiness and biodiversity due to selective grazing of palatable species (Bakker, 1985<ref>BAKKER J. P., DIJKSTRA M., RUSSCHEN P. T., 1985. Dispersa, germination and early establishment of halophytes and glycophytes on a grazed and abandoned salt‐marsh gradient. ''New Phytologist''. '''101''', 291-308.</ref>, 1998; Kiehl ''et al.'', 1996<ref>KIEHL K., EISCHEID I., GETTNER S., WALTER J., 1996. Impact of different sheep grazing intensities on salt-marsh vegetation in northern Germany. ''Journal of Vegetation Science''. '''7''', 99–106.</ref>; Adler ''et al.'', 2001<ref>ADLER P.B.; RAFF D.A.; LAUENROTH W.K.;, 2001.The effect of grazing on the spatial heterogeneity of vegetation. ''OECOLOGIA''. '''128(4)''': 465-479.</ref>; Bouchard ''et al.'', 2003<ref>BOUCHARD V.; TESSIER M.; DIGAIRE F.; VIVIER, J.P.; VALERY, L.; GLOAGUEN, J.C.; LEFEUVRE, J.C., 2003. Sheep grazing as management tool in Western European saltmarshes.InternationalCongress on Biodiversity Conservation and Management. ''COMPTES RENDUS BIOLOGIES''. '''326''', S148-S157.DOI: 10.1016/S1631-0691(03)00052-0.</ref>; Marriot ''et al.'' 2005). Patchiness may cause specific spatial patterns in turbulence and sedimentation (Boorman, 1999; van Wesenbeeck, ''et al.'', 2007), so that the sum effect of patchiness on marsh coastal protection is not known. Conversely, grazing pressure can lead to greater resource allocation of below‐ground biomass (Pucheta, ''et al.'', 2004<ref>PUCHETA, E.; BONAMICI, I.; CABIDO, M.; DIAZ, S.; 2004. Below-ground biomass and productivity of a grazed site and a neighbouring ungrazed exclosure in a grassland in central Argentina. ''AUSTRALECOLOGY''. '''29(2)''', 201-208.DOI: 10.1111/j.1442-9993.2004.01337.x. </ref>), thus reducing surface erosion and below-ground contributions to an increase in marsh surface elevation. <br />
</br><br />
<br />
<br />
==see also==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Salt_marshes |Salt marshes]]<br />
<br />
[[Natural_barriers#Salt_marshes | Natural barriers, salt marshes]]<br />
<br />
[[Salt_marches_in_Europe_and_temporal_variability |Salt marches in Europe and temporal variability]]<br />
</br><br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Salt marshes ]]<br />
[[Category: Coastal erosion ]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=25081<br />
|AuthorFullName1= van Belzen, Jim<br />
|AuthorID2=8361<br />
|AuthorFullName2= Bouma, Tjeerd<br />
|AuthorID3=20719<br />
|AuthorFullName3= Skov, Martin<br />
|AuthorID4=20751<br />
|AuthorFullName4= Zhang, Liquan<br />
|AuthorID5=?<br />
|AuthorFullName5= Yuan, Lin<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_salt_marshes&diff=50220Dynamics, threats and management of salt marshes2012-07-24T13:45:28Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
<br />
Coastal areas, like [[estuaries]], are high energetic environments where organisms are exposed to hydrodynamic forces from waves and tidal [[currents]]. Ecosystem engineering species (Jones ''et al.'', 1997) play an important role in shaping the [[intertidal]] landscape (Temmerman ''et al.'', 2007<ref name= "Temmerman">TEMMERMAN, S.; BOUMA, T.J.; VAN DE KOPPEL, J.; VAN DER WAL, D.; DE VRIES, M.B.; HERMAN, P.M.J.(2007). Vegetation causes channel erosion in a tidal landscape. ''Geology''. '''35(7)''', 631-634. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114118 www.vliz.be/imis]</ref>; Weerman ''et al.'', 2010). Coastal vegetation, like [[salt marsh]] vegetation, are ecosystem engineers in that they can strongly attenuate hydrodynamic energy from tidal current and [[waves]] (Bouma ''et al.'', 2005<ref name= "Bouma05">BOUMAT.J.,DE VRIES M.B., LOW E., PERALTA G., TNCZOSI.C.,VANDEKOPPELJ., HERMAN P. M. J., 2005. Trade‐offs Related to Ecosystem Engineering: A Case Study on Stiffness of Emerging Macrophytes. ''Ecology''. '''86''', 2187‐2199.</ref>, 2007<ref name= "Bouam07">BOUMA, T.J.; VAN DUREN, L.A.; TEMMERMAN, S.; CLAVERIE, T.; BLANCO-GARCIA, A.; YSEBAERT, T.J.; HERMAN, P.M.J. (2007). Spatial flow and sedimentation patterns within patches of epibenthic structures. ''Cont. Shelf Res.''. '''27(8)''': 1020-1045. dx.doi.org/10.1016/j.csr.2005.12.019<br />
Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=114437 www.vliz.be/imis]</ref>, 2010). This has a positive effect on sediment accretion rates, and hence results in increased sediment elevation. In turn, increased sediment elevation stimulates plant growth because the inundation duration for the vegetation is shortened. This results in positive feedbacks between plant growth and sediment accretion. Implications of this feedback can be observed in the field in the form of dome shaped hummocks of cord‐grass (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina spp.]''). They can be found on the [[Tidal flats from space|mud flats]] seaward of the salt marsh edge (Figure 1), where the salt marsh is developing.<br />
<br />
Feedbacks between hydrodynamic forces, sediment accretion and vegetation are key processes in shaping salt marshes (Temmerman ''et al.'', 2007<ref name= "Temmerman"/>; van Wesenbeeck ''et al.'', 2008). Locally the canopy of a vegetation stand can attenuate currents and waves which result in a net [[sedimentation]]. However, the same canopy also obstructs the flow, thereby diverting it and increasing flow velocities in the areas adjacent to the canopy because of conservation of mass and energy (Bouma ''et al.'', 2009). This biomechanical stress diversion can result in negative feedbacks on vegetation settlement and growth at some distance from the canopy (van Wesenbeeck ''et al.'', 2008). However, the outcome of these feedbacks may be dependent on the local context, seeing as these kinds of feedbacks are density‐dependent (Bouma ''et al.'', 2009). In other words, the strength of these negative feedbacks may vary with vegetation age, composition, or even the sediment type it is growing in (van Hulzen ''et al.'', 2006<ref name= "van Hulzen">VAN HULZEN J.,VAN SOELEN J.,HERMAN P.M.J., BOUMA T.J., 2006.The significance of spatial andtemporal patterns of algal mat deposition in structuring salt marsh vegetation. ''J Veget Sci.''. '''17''', 291‐298.</ref>). Overall these feedbacks cause complex patterns of gullies and hummocks until eventually a mature marsh arises, dissected by a complex drainage system (Kirwan and Murray, 2007; Temmerman ''et al.'', 2007<ref name= "Temmerman"/>).<br />
<br />
Many marshes are characterized by a cyclic nature, where marsh formation is followed by destruction (Figure 2). After a period of lateral extension, large scale lateral erosion of salt marshes can set in when the marsh edge becomes disturbed, a phenomenon often referred to as cliff erosion (see Figure 1.a, Figure 2.B.b; Allen, 2000<ref name= "Allen">ALLEN J.R.L., 2000. Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe. ''Quaternary Science Reviews''. '''19''', 1155-1231.</ref>; Adam 2002<ref name= "Adam">ADAM P., 2002. Salt marshes in a time of change. ''Environmental Conservation''. '''29''', 39‐61</ref>). For example, a disturbance from a [[storm surge]] can initialize this erosion process by forming a steep slope. At the disturbed edge, sediment is more vulnerable to wave action and currents. So once a cliff starts to erode, this process will not easily be stopped. Thus the steep slope remains particularly vulnerable for waves and currents until it is protected by new marsh vegetation emerging in front of the cliff. The initiation of cliff erosion is intrinsic to natural temporal salt marsh dynamics (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel">VAN DE KOPPEL J.,VAN DER WAL D., BAKKER J.P.,HERMAN P.M.J., 2005. Self‐Organization and Vegetation Collapse in Salt Marsh Ecosystems. ''The American Naturalist''. '''165''', E1-12.</ref>). However, human activities can contribute significantly to the severity of the cliff erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>). For example, shipping traffic and [[dredging]] activities can increase exposure to currents and waves, thereby increasing the pace at which lateral erosion proceeds. Moreover, human induced activities may also take away the space for natural marsh recovery in front of the eroding cliff. The latter would result in the permanent loss of a marsh.<br />
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Loss of salt marsh habitat due to lateral erosion is a major problem across the world, especially in those locations where the marsh does not seem to recover. For example, the marshes in the [[Biodiversity_and_conservation%2C_and_role_of_marine_protected_areas#Venice_Lagoon |Venice Lagoon]] (Italy) laterally erode with 1.2‐2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day">DAY J.W., SCARTON F., RISMONDO A., ARET D., 1998. Rapid Deterioration of a Salt Marsh in Venice Lagoon, Italy. ''Journal of Coastal Research''. '''14''', 583‐590.</ref>) .The estuaries of South‐East England lose about 4,000 m² <math>yr^{-1}</math> of tidal marsh area due to erosion at the seaward edges and channel widening of creeks dissecting the marsh (Hughes and Paramor, 2004<ref name= "Hughes">HUGHES R.G., PARAMOR O.A.L., 2004. On the loss of saltmarshes in south‐east England: methods for their restoration. ''Journal of Applied Ecology''. '''41''', 440‐448.</ref>). However, the main drivers of salt marsh erosion are still subject of debate (Wolters ''et al.'', 2005<ref name= "Wolters">WOLTERS M., BAKKER J.P., BERTNESS M.D., JEFFERIES R.L., MÖLLER I., 2005. Saltmarsh erosion and restoration in south-east England: squeezing the evidence requires realignment. ''Journal of Applied Ecology''. '''42''', 844‐851. </ref>). Generally, it is believed that human activities are responsible for increasing erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Pollution, shipping and dredging are some of the proposed [[anthropogenic]] causes. In addition, climate change and [[sea level rise]] receivemuch attention as a cause of salt marsh disappearance. In addition to these extrinsic forcing factors, intrinsic biological processes are also proposed (Allen, 2000<ref name= "Allen"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). For example, vegetation‐sediment feedbacks (Allen, 2000<ref name= "Allen"/>) and sediment destabilization by bioturbation and herbivory by worms (Hughes and Paramor, 2004<ref name= "Hughes"/>; van der Wal and Pye, 2004<ref name= "van der wal">VAN DER WAL D., PYE K., 2004. Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK). ''Geomorphology''. '''61''', 373‐391.</ref>) and geese (Dionne, 1985<ref>DIONNE, J.-C., 1985. Tidal marsh erosion by Geese, St. Lawrence estuary, Québec. ''Géographie physique et Quaternaire''. '''39''', 99‐105.</ref>) can also result in erosion of salt marshes. A fundamental understanding of the mechanisms that control cliff initiation and salt marsh re‐establishment in front of a cliff is needed in order to protect and manage these highly dynamic salt marsh ecosystems.<br />
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{|style="margin: 1em auto 1em auto;"<br />
|[[Image: Eroding cliff.JPG|thumb|left|300px| Figure 1: (A) Eroding cliff. (B) Patchy vegetation at pioneer zone of mudflat and saltmarsh interface. A dome-shaped patch is seen in front. (C) Salt marsh with eroding cliff separating the low marsh and pioneer zone. Pioneer vegetation (''Spartina'') has colonized the area below the eroding cliff (see also fig. 1.A). Photographs by J. van Belzen.]]<br />
|[[Image:overview of saltmarsh.JPG|thumb|none|300px| Figure 2: (A) Overview of saltmarsh by aerial photograph (RWS), comparable to situation (B.b). Cross-shoreprofile of salt‐marsh dynamics of conceptual ecomorphological model, which mimics the development of the marsh in (A). Here, (―) is the initial bare mud--‐flat profile, (―) is vegetated marsh profile at beginning, and (---) is the final profile. First, (a) saltmarsh generation due to the positive feedback between vegetation and sedimentation.Second, (b) cliff erosion of old marsh and subsequent growth at the pioneer zone (after van de Koppel, ''et al.'', 2005<ref name= "Van de Koppel"/>).]]<br />
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==VULNERABILITY & THREATS TO SALT MASRHES==<br />
===Short-term effects of flooding and storms===<br />
====SHORT-TERM FLOODING: Vulnerability of marshes to saltwater flooding====<br />
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The salt‐marsh community is well adapted to salinity due to regular tidal exposure to seawater. The vast majority of salt-marshes are well drained and therefore at less risk to the endured flooding. In comparison, the community of grazing-marshes is adapted to very dilute seawater and the habitat drainage is often slow. The potential impact of saltwater flooding is therefore more severe for [[Coastal_grazing_marsh| grazing marshes]] than for salt marshes. Much of the evidence regarding the effect of seawater on coastal vegetation therefore relates to oligohaline/grazing marshes.<br />
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====SHORT-TERM FLOODING: Effect of flooding by saline water on salt marshes ====<br />
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A flooding event that originates from increased freshwater discharge, for instance due to heavy rainfall or ice melt in a catchment area, will result in a fresh‐water pulse through downstream marshes. Unless freshwater flooding lingers for extensive periods, the impact on the vegetation of salt-and grazing- marshes will be short lived (Flynn ''et al.'', 1995<ref name= "Flynn">FLYNN, K.M.; MCKEE, .KL.; MENDELSSOHN, I.A, 1995.RECOVERY OF FRESH-WATER MARSH VEGETATION AFTER A SALTWATER INTRUSION EVENT.'' OECOLOGIA''. '''103(1)''', 63-72 DOI:10.1007/BF00328426.</ref>; Grace and Ford, 1996<ref name= "Grace">GRACE J.B., FORD M.A., 1996. The potential impact of herbivores on the susceptibility of the marsh plant ''Sagittaria lancifolia'' to saltwater intrusion in coastal wetlands. ''Estuaries''. '''19''', 13–20.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard">HOWARD R.J., MENDELSSOHN I.A., 2000. Structure and composition of oligohaline marsh plant communities exposed to salinity pulses. ''Aquat Bot''. '''68''', 143–164.</ref>). The [[Halophytic_plants|‘halophytic’]] (salt-tolerant) species that dominate salt-and grazing-marsh communities will not be harmed by short‐term fresh water exposure. However, their physiological and biochemical adaptations to cope with salinity stress make them poorly competitive under fresh water conditions (Crain ''et al., 2004''<ref name= "Crain">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549.DOI: 10.1890/03-0745 </ref>). Their halophytic traits enable them to colonise saline environments (Pennings and Callaway, 1992<ref name= "Pennings">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549. DOI: 10.1890/03-0745 </ref>). Salinity exposure in the salt marsh, and consequently the inherent salt tolerance of the inhabitant community, does not necessarily decline linearly with shore level. Summer evaporation of seawater pools can leave concentrated deposits of salt on the high marsh where the habitat is infrequently flushed, leading to high levels of sediment salinity that exclude less halophytic species (Watson and Burne, 2009). Paradoxically, increased frequency of seawater flushing by storms might dilute the accrued sediment salinity of such high marsh environments and alter the zonation of species. For instance, increased tidal flooding of an elevated marsh plain can cause the normally very halophytic high marsh species to be replaced by salt‐intolerant lower shore species (Watson and Burne, 2009).<br />
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The severity of impact of salt water flowing is likely to depend on the natural salinity occurring at a specific location. Relatively brackish-marshes, dominated by halophytic plants, will see less changes to community composition than fresh water dominated grazing marshes and coastal flood plains (Brown ''et al.'', 1994). Increased flooding by salt water is most likely to have the greatest effect on the fresh‐water adapted members of the marsh vegetation (Crain ''et al.'', 2004<ref name= "Crain"/>), which increases in dominance in the transitional and grazing‐marsh above the tidal marks. Stormy conditions that result in a temporary increase in sea level and which bring in salt water pulses to coastal marsh systems therefore should have a greater effect on the grazing‐marsh community than on the salt marsh community. For example, seawater flooding of a diked grazing-marsh, following a dike breaching, prevented most of the fresh water vegetation from developing in the following spring (Klein and Bateman, 1998<ref name= "Klein">KLEIN R.J.T., BATEMAN I.J., 1998. The recreational value of Cley marshes nature reserve: An argument against managed Retreat? ''Water and Environment Journal''. '''12''', 280-285. </ref>). Vegetation cover, species richness, recovery and re-establishment of an oligohaline marsh decreased during one month of experimental exposures to increased salinity (from 0.5‐5.0 salinity up to 12) (Howard and Mendelssohn, 2000<ref name= "Howard"/>). In the longer term, the space left by dead vegetation is likely to be colonised by more salinity tolerant species, and thus grazing-marsh communities might come to resemble those of salt marshes (Doody, 1982<ref name= "Doody">DOODY J.P., 1982. Sea defence and nature conservation: threat or opportunity. ''Aquat Conserv Mar Freshw Ecosyst'', '''2''', 275-283.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard"/>).<br />
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Many coastal marsh plants are able to recover temporary increases in salinity (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Grace and Ford, 1996<ref name= "Grace"/>; Howard and Mendelssohn, 2000<ref name= "Howard"/>). However, the potential for lasting changes to communities increases with the duration of flooding (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Howard and Mendelssohn 2000<ref name= "Howard"/>). Elevated salinity (from natural, 0.5‐5 to 15) slowed vegetation recovery more in flooded than in drained soils (Flynn ''et al.'', 1995<ref name= "Flynn"/>). The naturally slow drainage of grazing marshes, that follows temporary sea water flood, causes this habitat to remain immersed for longer periods than salt marshes. Grazing marshes are therefore at greater risk to the endured flooding. However, there are indications that these marshes are relatively resilient to exposure; if the water is brackish enough, it may require months of immersion before significant impacts to vegetation cover occurs (e.g. Howard and Mendelssohn, 2000<ref name= "Howard"/>). Brewer and Grace (1990)<ref>BREWER J.S., GRACE J.B., 1990. Plant community structure in an oligohaline tidal marsh. ''Vegetatio''. '''90''', 93–107.</ref> hypothesized that occasional storm‐generated pulses of salt water moving into an oligohaline marsh would generate short-lived salinity gradients that, along with biotic interactions, would regulate species distributions over longer terms. Sharpe and Balwin (2009)<ref name= "Sharpe">SHARPE P. J., BALWIN A.H., 2009. Patterns of Wetland Plant Species Richness Across Estuarine Gradients of Chesapeake Bay. ''Wetlands''. '''29''', 225-235.</ref> proposed that an unexpected peak in vegetation species richness in the transitional marsh arose because pulsed variation in salinity (0‐5) prevented domination by fresh water or salt water species. Thus, pulsed salinity exposure might not necessarily diminish vegetation diversity. Nevertheless, increased salt water flooding of grazing marshes is likely to drive the succession towards more salt-tolerant vegetation, and increase the resemblance with salt marsh assemblages. Note that the empirical evidence for the rate of this transition is lacking (Nicholls and Wilson, 2001<ref name= "Nicholls">NICHOLLS R.J., WILSON T., 2001. Chapter five. Integrated impacts on coastal areas and river flooding. In: Holman I.P., Loveland P.J. (Eds), Regional Climate Change Impact and Response Studies in East Anglia and North West England (RegIS). Final Report of MAFF project no. CC0337. (downloadable at [http://www.ukcip.org.uk www.ukcip.org.uk]).</ref>). The consequence of increased coastal flooding might therefore be a gradual loss of grazing-marsh communities, in exchange for gain in area cover of salt marsh communities (Doody, 1982<ref name= "Doody"/>; Klein and Bateman, 1998<ref name= "Klein"/>; Nicholls and Wilson, 2001<ref name= "Nicholls"/>). <br />
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====SHORT-TERM FLOODING: Interactions of salinity with other disturbances ====<br />
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It is important to caution against a general interpretation that seawater flooding is a minimal risk to coastal marshes in general. The severity of seawater influence on grazing‐marshes might depend much on whether the salinity is paralleled with other plant stressors and disturbances. Sharpe and Balwin (2009)<ref name= "Sharpe"/> sampled plant diversity in a marsh in the United States, across a fresh (salinity 0.5) to mesohaline (5-18) salinity gradient. In an undisturbed marsh, richness in transition zone oligohaline marshes was as high as or higher than in tidal fresh water-marshesIn an anthropogenically disturbed estuary, however, plant species richness declined linearly with an increase in salinity. Experimental flooding by brackish (6‐14) water had a greater effect on grazing‐marsh community structure and [[biomass]] when the vegetation was also disturbed by leaf clipping (Baldwin and Mendelssohn, 1998) or grazing (Gough and Grace, 1998). In comparison, flooding did not affect species richness in the absence of such additional disturbances (Baldwin and Mendelssohn, 1998). If the salinity and water regimes are permanently altered and/or the vegetation is destroyed by a combination of factors, the substrate might eventually subside. Substrate [[Natural_causes_of_coastal_erosion#Subsidence |subsidence]] and associated increased water depth might prevent seed dispersal and germination of more flooding tolerant species, and thus hamper system recovery (McKee and Mendelssohn, 1989<ref name= "Mckee en M">MCKEE K.L.; MENDELSSOHN I.A.,1989. Response of a fresh-water marsh plant community to increased salinity and increased water level. ''AQUATIC BOTANY''. '''34(4)''', 301-316. DOI: 10.1016/0304-3770(89)90074-0.</ref>).It is not known beyond which threshold the frequency of flooding will have permanent effects.<br />
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====SHORT-TERM: Vulnerability of marshes to storm damage====<br />
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As mentioned above, flooding can induce some disturbances to the vegetation composition of salt marshes. However, the threat storms impose on salt marshes is more likely to result from storm-associated damage than from flooding. Wind-induced waves can destabilize sediments, initiate and propagate lateral cliff erosion, tear of plant material, as well as deposits of wrack and debris in marshes. The [[vulnerability]] of salt marshes is largely related to the effects of waves on sediment stability and on lateral erosion. The evidence we present for the effects of storm associated erosion mostly originates from salt marshes seeing as the literature on grazing-marsh damage from salt water erosion is scarce. Severe salt marsh erosion will undoubtedly lead to an increased risk of sea water flooding and storm-associated damage for adjoined grazing‐marshes, and might eventually drive a transition of grazing‐marsh communities into salt marsh habitats.<br />
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====SHORT-TERM STORM: Sediment destabilization and lateral erosion of salt marshes====<br />
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Storm events can induce sediment stabilization and lateral erosion, which can have an important impact on the dynamics and functioning of salt marshes. Although lateral erosion is an intrinsic process for salt marshes and part of the natural cyclic behaviour, it generally gets initiated by a storm (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Such cyclic behaviour requires sufficient space for marshes to migrate landward. This space is nowadays being diminished due to anthropogenic land use. Hence, the lateral erosion of salt marshes has become a global threat, as it is unclear under which conditions an eroding marsh can re‐establish in the limited available space. For example, the marshes in the Venice Lagoon (Italy) erode 1.2-2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day"/>) and estuaries of South-East England lose ~4,000 m² of tidal marsh per annum from erosion at the seaward edges and widening of creeks within the marsh (Hughes and Paramor, 2004<ref name= "Hughes"/>). In these locations, large areas of marsh are lost due to cliff erosion with little or no recovery of the vegetation. <br />
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It is clear that storms contribute significantly to the loss by lateral erosion. However, the main driving factors initiating this erosion are still not clear (Wolters ''et al.'', 2005<ref name= "Wolters"/>). Human activities can be, in part, responsible for increasing erosion rates through [[pollutant]]-driven diminishing of vegetation cover and/or by enhancing hydrodynamic energy reaching the marsh via ship waves and channel dredging (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Thus, there is a strong need for a fundamental understanding of the cyclic functioning of salt marsh ecosystems in order to understand when disturbances by storms will start a natural cycle of rejuvenation versus when they cause the irreversible loss of a marsh and thus would benefit from protective measures. <br />
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Vulnerability of the saltmarsh to the initiation of cliff erosion will largely depend on the age of the marsh. Cliff erosion is hypothesized to be an inevitable and intrinsic consequence of the ecomorphological dynamics of saltmarshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). That is, the capture of sediment by the vegetation leads to vertical salt marsh growth, which in the long term makes the salt marsh susceptible to lateral erosion (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). Both conceptual modelling and empirical evidence showed that a positive feedback between vegetation growth and sediment capture generates an increasingly steeper bank at the seaward edge of the marsh (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). As a consequence, salt‐marsh edges become more vulnerable to disturbance as they mature (see Figure 1.B). This means that in the end, relatively small disturbances like from minor storm events or ship waves may induce the erosion. Data on sedimentation in salt-marshes, obtained from sediment core transects and spatiotemporal analysis of aerial photographs, support this conceptual model (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal">VAN DER WAL D., WIELEMAKER-VANDENDOOL A., HERMANP.M.J., 2008. Spatial patterns, rates and mechanisms of saltmarsh cycles (Westerschelde, The Netherlands). ''Estuarine, Coastal and Shelf Science''. '''76''', 357‐368. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=143078 www.vliz.be/imis].</ref>), suggesting that, in a wide range of circumstances, lateral retreat due to cliff erosion will happen sooner or later. <br />
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[[Resilience]] of the marsh edge to erosion will depend on the interplay between vegetation composition and sediment dynamics. For instance, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina]'' plants reduce cliff erosion more than ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=232101 Limonium]'' plants do due to differences in their root system. As a consequence, a ''Spartina'' dominated marsh edge is likely less vulnerable to storm events (van Eerdt, 1985). However, consequences of plant community on the vulnerability and resilience of the marsh can be more complex. The above ground plant traits can have other effects on the vegetation-sediment interaction. For example, stiffness and density of the plant may affect sedimentation rates (Bouma ''et al.'', 2005<ref name= "Bouma05"/>, 2009, 2010). The overall effect of above and below plant traits on salt‐marsh resilience/vulnerability remains largely unknown and subject to ongoing research. <br />
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Alongside cliff erosion, re‐growth of pioneer vegetation on the cleared mudflat in front of the saltmarsh cliff ideally occurs, thereby rejuvenating the mature marsh (see Figure.1.B; van de Koppel, ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>). This pioneer vegetation determines the conditions for lateral retreat and gradually slows down erosion of the salt-marsh edge. <br />
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The establishment of pioneer vegetation is therefore of vital importance for the development and recovery of salt marshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>; Callaghan ''et al.'', 2010<ref name= "callaghan">CALLAGHAN, D.P.; BOUMA, T.J.; KLAASSEN, P.; VAN DER WAL, D.; STIVE, M.J.F.; HERMAN, P.M.J., 2010. Hydrodynamic forcing on salt-marsh development: Distinguishing the relative importance of waves and tidal flows Est., ''Coast. and Shelf Sci.''. '''89(1)''', 73-88. dx.doi.org/10.1016/j.ecss.2010.05.013. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=206900 www.vliz.be/imis].</ref>). This emphasizes the importance of initial conditions for the establishment and growth of vegetation, and the physical conditions that may constrain these intrinsic processes for salt marsh development (van der Wal ''et al.'', 2008<ref name= "VdWal"/>). However, the factors limiting seedling establishment remain poorly understood (Bouma ''et al.'', 2009). We hypothesize that sediment destabilization plays a critical role in the ability for pioneer establishment on a mudflat and, therefore, in the ability of the salt marsh to recover from lateral cliff erosion (Balke ''et al.'', submitted; Bouma ''et al.'', submitted; van Belzen ''et al.'', in prep a; Infantes ''et al.'', submitted). <br />
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====SHORT-TERM STORM: sediment and wrack deposits on salt marshes====<br />
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Depositions of wrack, debris or large amounts of sediment, associated with extreme flooding events, can have significant effects on salt marsh vegetation. Wrack depositions may smother less hardy vegetation, leaving bare patches and opportunity for new colonization by neighbouring species, or from dispersed seeds (Bertness and Ellison, 1987<ref>BERTNESS M.D., ELLISON A.M., 1987. Determination of pattern in a New England salt marsh plant community. ''Ecol Monogr''. '''57''', 129‐14.</ref>; Tolley and Christian, 1999<ref name= "Tolley">TOLLEY P.M.; CHRISTIAN R.R., 1999. Effects of increased inundation and wrack deposition on a high salt marsh plant community. ''ESTUARIES''. '''22(4)''', 944-954.DOI: 10.2307/1353074.</ref>). Large algal mats can have residence times of 3‐4 months (Valiela and Rietsma, 1995<ref name= "Valiella">VALIELA I.; RIETSMA C.S.,1995. DISTURBANCE OF SALT-MARSH VEGETATION BY WRACK MATS IN GREAT-SIPPEWISSETT-MARSH. ''OECOLOGIA''. '''102(1)''', 106-112. </ref>). While wrack depositions may not be as significant in cover (Valiela and Rietsma, 1995<ref name= "Valiella"/>), small-scale alteration in species cover by algal wrack depositions does have the potential for wider effects on community diversity if the same spots are regularly covered by seaweed (van Hulzen ''et al.'', 2006<ref name= "van Hulzen"/>). The deposition of sediments following storm flooding may be significant. Experimental flooding and sedimentation of seedbanks of an oligohaline marsh community showed that an addition of 2 cm of sediment decreased plant density and germination of seedlings, suggesting that an increase in sedimentation and relative sea level may reduce plant biodiversity (Peterson and Baldwin, 2004<ref>PETERSON J.E., BALDWIN A.H., 2004. Seedling emergence from seed banks of tidal freshwater wetlands: response to inundation and sedimentation. ''Aquat Bot''. '''78,''' 243–254. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=59970 www.vliz.be/imis].</ref>]). The deposition of sediments might be positive for subducting and nutrient starved marshes. For example, within a year after 3-8 cm of sediment deposited by Hurricane Katrina, the vegetation of a high marsh had fully recovered and below‐ground root growth had increased 10‐fold (McKee and Cherry, 2009<ref name= "Cherry">MCKEE K.L., CHERRY J.A., 2009. Hurricane Katrina sediment slowed elevation loss in subsiding brackish marshes of the Mississippi river delta. ''Wetlands''. '''29''', 2-15.</ref>).<br />
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While single factors may have limited effects on marshes, a collective of concurrent stressors is likely to generate significant impacts on marsh communities. The deposition of wrack and sediments is often concurrent with other habitat stressors that might jointly influence marsh vegetation cover. Thus, while Tolley and Christian (1999)<ref name= "Tolley"/> found little effect of sea water flooding on vegetation biomass, the simultaneous deposition of algal wrack greatly repressed plant cover and biomass, in some species irreversibly so.<br />
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===Long-term effects due to climate change and sea level rise===<br />
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[[Coastal squeeze]], due to sea level rise, and erosion are primary threats to salt marshes across Europe. They can result in reduced coastal defence value and in an increased risk of flooding. Although sea level rise may pose serious threats to the survival of salt marshes, there is growing evidence that as long as sediment supply is sufficient, the vegetation-sedimentation feedback of marshes enables marshes to accrete vertically at the rate of the rising sea-level (Kirwan and Temmerman, 2009<ref name= "KenT">KIRWAN M., TEMMERMAN S., 2009. Coastal marsh response to historical and future sea-level acceleration. ''Quaternary Science Reviews''. '''28''', 1801-1808.</ref>). However, if the suspended matter load is reduced by climate change or by significant human alteration in a catchment area, vegetation- sedimentation feedbacks can become limited, affecting the potential of marshes to accrete (Kirwan and Temmerman, 2009<ref name= "KenT"/>). As explained in the previous sections, lateral marsh erosion can become a serious threat to salt marshes over time if seedling establishment in front of the marsh is not possible so that re- growth of the marsh is prevented. Many aspects that affect the cyclic dynamics of marshes are still not well understood. Important in maintaining the vegetation-sedimentation feedback is that the sedimentary conditions remain more or less the same.<br />
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Several managerial aspects are likely to compromise the capacity for marshes to persist and to protect the coast. Reduction in area by coastal squeeze will reduce the wave attenuation capacity, as the efficiency of energy reduction is strongly dependent on the depth of the marsh (Möller, 2006<ref name= "Moller">MÖLLER I., 2006. Quantifying saltmarsh vegetation and its effect on wave height dissipation: Results from a UK East coast saltmarsh. ''Estuarine Coastal and Shelf Science''. '''69''', 337‐351.</ref>). Whether this might have negative feedback on marsh accretion and accelerate area loss is not known. Effects of grazing might also reduce the vegetation‐sedimentation feedback by reducing vegetation cover and height, thereby hampering the development of salt marshes (Kiehl ''et al.'', 2007<ref name= "Kiehl07">KIEHL K., SCHRÖDER H., STOCK M., 2007. Long‐term vegetation dynamics after land‐use change in Wadden Sea salt marshes. ''Coastline Reports''. '''7''', 17‐24.</ref>). Finally, very little is known about the implications on salt marsh resilience from interactions between different environmental, climatic and managerial variables. Interactions between climate stressors (e.g. desiccation, irradiation), physical forcing (extreme flooding events, increased storminess) and environmental management (eutrophication, grazing, and managed retreat) will be a likely reality for many marshes. This is important because interactive stresses can be synergistic and cause shifts in the stable states of ecosystems, which can compromise the naturally delivered services (Scheffer ''et al.'', 2001<ref>SCHEFFER M., CARPENTER S., FOLEY J.A., FOLKER C., WALKER B., 2001. Catastrophic shifts in ecosystems. ''Nature''. '''413''': 591‐596. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=19763 www.vliz.be/imis].</ref>; Scheffer ''et al.'', 2009<ref>SCHEFFER M., BASCOMPTE J.,BROCK W. A., BROVKIN V., CARPENTER S., DAKOS V.,HELD H., VANNESE.H., RIETKERK M., SUGIHARA G., 2009. Early-warning signals for critical transitions. ''Nature''. '''461''', 53‐59. </ref>). Our evaluation of the resilience of salt marshes to disturbance, including climate change, might for the time being still be somewhat naïve and based on limited current research. <br />
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====CASE STUDY: FORECASTING THE EFFECTS OF SEA‐LEVEL RISE====<br />
[[Image: Chongming Dongtan.JPG|thumb|right|300px|Figure 3: Impact of sea-level rise on tidal flat and tidal marsh complex by 2050 (a and b) and 2100 (c and d) year at Chongming Dongtan nature reserve.]]<br />
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Located at the mouth of the Yangtze Estuary, the Chongming Dongtan nature reserve is extremely vulnerable to climate change and especially to an accelerated sea-level rise. We use a variety of data from [[remote sensing]], an in situ global positioning system (GPS), tidal gauges, nautical charts, geographic spatial analysis modelling gand IPCC sea-level rise scenarios to forecast the potential impacts of increased sea level on the coastal wetland habitat of the Chongming Dongtan Nature Reserve (Figure 3). The results indicate that around 40% of the intertidal zone of the nature reserve will be inundated by the year 2100 due to an estimated 0.88 m increase in sea level (Figure 3.c and 3.d). In particular, the ''Scirpus mariqueter'' communities and bare tidal flats are more vulnerable to sea‐level rise. The identification, mapping and statistical summary of environmental impacts of the projected sea-level rise at Chongming Dongtan Nature Reserve represent an important initial step for decision makers concerned with mitigation of the adverse impacts of sea-level rise. In this study, the inundation‐based assessment was developed to inform policymakers, managers and the public about the amount and the spatial distribution of tidal wetland change as a result of sea‐level rise. The results indicate that the zones most vulnerable to sea-level rise at the Chongming Dongtan Nature Reserve is the ''S. Mariqueter'' zone, the bare tidal flat zone and the tidal creeks, which are the most suitable habitats for migratory birds. A ~30% loss of the ''S. Mariqueter'' marsh community by the year 2100 would eliminate a rich invertebrate food source and cause deterioration in the estuarine food web for migrating birds; such a loss could arise from human-induced stressors such as land reclamation, seawall constructions, overfishing and local pollution. As tidal marshes and flats submerge and decline in size and productivity, increased crowding in the remaining areas could lead to reductions in and eventually even exclusion of some local shorebird populations (Tian ''et al.'', 2010<ref>TIAN, B; ZHANG, LQ ; WANG, XR; ZHOU, YX ; ZHANG, W.; 2010. Forecasting the effects of sea-level rise at Chongming Dongtan Nature Reserve in the Yangtze Delta, Shanghai, China. ''ECOLOGICALENGINEERING'', '''36(10)''': 1383-1388.DOI: 10.1016/j.ecoleng.2010.06.016.</ref>). <br />
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==KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY ==<br />
===Effects of single disturbance events on marsh responses to long-term change===<br />
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Single events, such as violent storms, normally have short-lived effects on the species composition and on the ecological functioning of salt-marshes (Flynn ''et al.'' 1995<ref name= "Flynn"/>, Howard and Mendelssohn, 2000<ref name= "Howard"/>; McKee and Cherry, 2009<ref name= "Cherry"/>), and are thus of less importance compared to long term persistent changes in environmental condition. Long-term processes of coastal squeeze with sea level rise and lateral erosion with increased storminess are considered to be the primary threats to salt- and grazing-marshes across Europe (Nicholls and Wilson, 2001<ref name= "Nicholls"/>. A single storm can push a marsh over the tipping point, shifting it from laterally expanding towards laterally eroding. If erosion persists, and the marsh cannot re-establish in front of the cliff, in time this will result in reduced coastal defence value and an increased risk of flooding of adjacent terrestrial environment (e.g. grazing- marshes) (Klein and Bateman, 2007).<br />
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==CURRENT MANAGEMENT PRACTICES==<br />
===Making space for water===<br />
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Currently, salt-marshes are managed extensively because of their acknowledged role in coastal protection. Many countries like e.g. the UK, the Netherlands, etc, have developed management schemes in order to make space for water along river flood plains, estuarine and coastal areas (Bakker, ''et al.'', 2005; DEFRA, 2004). This way, river run‐off and occasional high sea water levels can be attenuated by the natural buffer and retention capacity of the landscape. For example, restoring the water storage volume in an estuary can reduce the tidal prism, smoothing the tidal amplitude, which reduces the risk of flooding in up-stream estuarine areas. Salt‐marshes play an important part in this contemporary policy, because creating new marsh‐land both increases tidal water storage in up‐stream estuarine areas and wave attenuation of storm surges along exposed coast lines (Bakker ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>).<br />
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===Managed retreat/realignment and salt-marsh engineering===<br />
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The current effort to restore marsh systems in Europe and elsewhere represents graphic evidence of the political and managerial value placed on the goods and services provided by this ecosystem. The principle of ‘managed realignment’ and ‘managed retreat’ comes down to allowing salt-marsh areas, that were historically converted to alternative use for anthropogenic purposes (e.g. agricultural land or tourist development), to return to their natural state and area cover (Garbutt, ''et al.'', 2006<ref>GARBUTT, R.A.; READING, C.J.; WOLTERS, M.; GRAY, A.J.; ROTHERY, P., 2006. Monitoring the development of intertidal habitats on former agricultural land after the managed realignment of coastal defences at Tollesbury, Essex, UK. ''MARINE POLLUTION BULLETIN''. '''53(1-4)''', 155-164. DOI: 10.1016/j.marpolbul.2005.09.015.</ref>). This can be done in a number of ways, but typically involves making a breach in the historically erected barrier (seawall, dike) rather than removing the whole structure. This approach reduces the costs involved, as well as the wave action depressing the development of the vegetation. Cost benefit analyses typically show a net advantage of managed realignment over other constructed defence options (Turner, ''et al.'', 2007<ref>TURNER, R.K.; BURGESS, D .; HADLEY, D.; COOMBES, E.; JACKSON, N.; 2007. A cost-benefit appraisal of coastal managed realignment policy. ''GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS''. '''17(3-4)''': 397-407.DOI: 10.1016/j.gloenvcha.2007.05.006.</ref>). Full restoration of natural ecosystem function has met some complications. The substrates and biodiversity of pristine salt marshes is often markedly different from an artificial or restored system, even 100 years after natural processes have been allowed to operate (Hazelden and Boorman, 2001<ref>HAZELDEN J.; BOORMAN L.A.; 2001.Soils and 'managed retreat' in South East England.''SOIL USE AND MANAGEMENT''. '''17(3)''':150-154. DOI: 10.1079/SUM200166.</ref>). The implications of this managed realignment on coastal protection by marshes are not known. The MOSE project of the Venice lagoon is an impressive example of large-scale engineering to create salt‐marsh wetlands, largely for their role in dampening wave action and erosion within the lagoon (MOSE 2010).<br />
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===Grazing management and coastal protection===<br />
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There is evidence to suggest that grazing management could be of particular importance to the capacity of marshes for protecting the coast, although there has been little quantitative research on this subject (Bakker, ''et al.'', 2005). The vegetation is of key importance to coastal protection by marshes, through consolidation of the soil and by representing a structural hindrance to wash-over waves. Evidently, livestock has large potential for altering the vegetation structure directly through feeding and indirectly by altering the conditions for vegetation growth (Bakker, ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>). Feeding and defecation moderate vegetation structure‐composition and above- and below-ground biomass production. Trampling and hoof holes lead to soil compaction and can cause saltpan formation (Vera, 2000<ref>VERA F.W.M., 2000. Grazing Ecology and Forest History. CABI Publishing, Wallingford, UK.</ref>). The potential of management of grazing regime to influence the salt marsh coastal protection potential is therefore high. Intense grazing modifies zonation patterns and transforms complex communities with woody species into homogenous lawns dominated by short flexible grass (Andresen, ''et al.'', 1990<ref name= "Andersen">ANDRESEN H., BAKKER J.P., BRONGERS M., HEYDEMANN B., IRMLER U., 1990. Long‐term changes of salt-marsh communities by cattle grazing. ''Vegetatio''. '''89''', 137–148.</ref>; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>), with an associated likely reduction in wave attenuation (Möller, 2006<ref name= "Moller"/>) and sedimentation rates (Andresen, ''et al.'', 1990<ref name= "Andersen"/>). Grazing at low intensity increases vegetation patchiness and biodiversity due to selective grazing of palatable species (Bakker, 1985<ref>BAKKER J. P., DIJKSTRA M., RUSSCHEN P. T., 1985. Dispersa, germination and early establishment of halophytes and glycophytes on a grazed and abandoned salt‐marsh gradient. ''New Phytologist''. '''101''', 291-308.</ref>, 1998; Kiehl ''et al.'', 1996<ref>KIEHL K., EISCHEID I., GETTNER S., WALTER J., 1996. Impact of different sheep grazing intensities on salt-marsh vegetation in northern Germany. ''Journal of Vegetation Science''. '''7''', 99–106.</ref>; Adler ''et al.'', 2001<ref>ADLER P.B.; RAFF D.A.; LAUENROTH W.K.;, 2001.The effect of grazing on the spatial heterogeneity of vegetation. ''OECOLOGIA''. '''128(4)''': 465-479.</ref>; Bouchard ''et al.'', 2003<ref>BOUCHARD V.; TESSIER M.; DIGAIRE F.; VIVIER, J.P.; VALERY, L.; GLOAGUEN, J.C.; LEFEUVRE, J.C., 2003. Sheep grazing as management tool in Western European saltmarshes.InternationalCongress on Biodiversity Conservation and Management. ''COMPTES RENDUS BIOLOGIES''. '''326''', S148-S157.DOI: 10.1016/S1631-0691(03)00052-0.</ref>; Marriot ''et al.'' 2005). Patchiness may cause specific spatial patterns in turbulence and sedimentation (Boorman, 1999; van Wesenbeeck, ''et al.'', 2007), so that the sum effect of patchiness on marsh coastal protection is not known. Conversely, grazing pressure can lead to greater resource allocation of below‐ground biomass (Pucheta, ''et al.'', 2004<ref>PUCHETA, E.; BONAMICI, I.; CABIDO, M.; DIAZ, S.; 2004. Below-ground biomass and productivity of a grazed site and a neighbouring ungrazed exclosure in a grassland in central Argentina. ''AUSTRALECOLOGY''. '''29(2)''', 201-208.DOI: 10.1111/j.1442-9993.2004.01337.x. </ref>), thus reducing surface erosion and below-ground contributions to an increase in marsh surface elevation. <br />
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==see also==<br />
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[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
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[[Salt_marshes |Salt marshes]]<br />
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[[Natural_barriers#Salt_marshes | Natural barriers, salt marshes]]<br />
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[[Salt_marches_in_Europe_and_temporal_variability |Salt marches in Europe and temporal variability]]<br />
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==References==<br />
<references/></br><br />
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[[Category: Salt marshes ]]<br />
[[Category: Coastal erosion ]]<br />
[[Category: Biodiversity and habitat loss]]<br />
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{{ 5Authors<br />
|AuthorID1=25081<br />
|AuthorFullName1= van Belzen, Jim<br />
|AuthorID2=8361<br />
|AuthorFullName2= Bouma, Tjeerd<br />
|AuthorID3=20719<br />
|AuthorFullName3= Skov, Martin<br />
|AuthorID4=20751<br />
|AuthorFullName4= Zhang, Liquan<br />
|AuthorID5=?<br />
|AuthorFullName5= Yuan, Lin<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_salt_marshes&diff=50215Dynamics, threats and management of salt marshes2012-07-24T13:29:55Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
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==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
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Coastal areas, like [[estuaries]], are high energetic environments where organisms are exposed to hydrodynamic forces from waves and tidal [[currents]]. Ecosystem engineering species (Jones ''et al.'', 1997) play an important role in shaping the [[intertidal]] landscape (Temmerman ''et al.'', 2007<ref name= "Temmerman">TEMMERMAN, S.; BOUMA, T.J.; VAN DE KOPPEL, J.; VAN DER WAL, D.; DE VRIES, M.B.; HERMAN, P.M.J.(2007). Vegetation causes channel erosion in a tidal landscape. ''Geology''. '''35(7)''', 631-634. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114118 www.vliz.be/imis]</ref>; Weerman ''et al.'', 2010). Coastal vegetation, like [[salt marsh]] vegetation, are ecosystem engineers in that they can strongly attenuate hydrodynamic energy from tidal current and [[waves]] (Bouma ''et al.'', 2005<ref name= "Bouma05">BOUMAT.J.,DE VRIES M.B., LOW E., PERALTA G., TNCZOSI.C.,VANDEKOPPELJ., HERMAN P. M. J., 2005. Trade‐offs Related to Ecosystem Engineering: A Case Study on Stiffness of Emerging Macrophytes. ''Ecology''. '''86''', 2187‐2199.</ref>, 2007<ref name= "Bouam07">BOUMA, T.J.; VAN DUREN, L.A.; TEMMERMAN, S.; CLAVERIE, T.; BLANCO-GARCIA, A.; YSEBAERT, T.J.; HERMAN, P.M.J. (2007). Spatial flow and sedimentation patterns within patches of epibenthic structures. ''Cont. Shelf Res.''. '''27(8)''': 1020-1045. dx.doi.org/10.1016/j.csr.2005.12.019<br />
Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=114437 www.vliz.be/imis]</ref>, 2010). This has a positive effect on sediment accretion rates, and hence results in increased sediment elevation. In turn, increased sediment elevation stimulates plant growth because the inundation duration for the vegetation is shortened. This results in positive feedbacks between plant growth and sediment accretion. Implications of this feedback can be observed in the field in the form of dome shaped hummocks of cord‐grass (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina spp.]''). They can be found on the [[Tidal flats from space|mud flats]] seaward of the salt marsh edge (Figure 1), where the salt marsh is developing.<br />
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Feedbacks between hydrodynamic forces, sediment accretion and vegetation are key processes in shaping salt marshes (Temmerman ''et al.'', 2007<ref name= "Temmerman"/>; van Wesenbeeck ''et al.'', 2008). Locally the canopy of a vegetation stand can attenuate currents and waves which result in a net [[sedimentation]]. However, the same canopy also obstructs the flow, thereby diverting it and increasing flow velocities in the areas adjacent to the canopy because of conservation of mass and energy (Bouma ''et al.'', 2009). This biomechanical stress diversion can result in negative feedbacks on vegetation settlement and growth at some distance from the canopy (van Wesenbeeck ''et al.'', 2008). However, the outcome of these feedbacks may be dependent on the local context, seeing as these kinds of feedbacks are density‐dependent (Bouma ''et al.'', 2009). In other words, the strength of these negative feedbacks may vary with vegetation age, composition, or even the sediment type it is growing in (van Hulzen ''et al.'', 2006<ref name= "van Hulzen">VAN HULZEN J.,VAN SOELEN J.,HERMAN P.M.J., BOUMA T.J., 2006.The significance of spatial andtemporal patterns of algal mat deposition in structuring salt marsh vegetation. ''J Veget Sci.''. '''17''', 291‐298.</ref>). Overall these feedbacks cause complex patterns of gullies and hummocks until eventually a mature marsh arises, dissected by a complex drainage system (Kirwan and Murray, 2007; Temmerman ''et al.'', 2007<ref name= "Temmerman"/>).<br />
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Many marshes are characterized by a cyclic nature, where marsh formation is followed by destruction (Figure 2). After a period of lateral extension, large scale lateral erosion of salt marshes can set in when the marsh edge becomes disturbed, a phenomenon often referred to as cliff erosion (see Figure 1.a, Figure 2.B.b; Allen, 2000<ref name= "Allen">ALLEN J.R.L., 2000. Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe. ''Quaternary Science Reviews''. '''19''', 1155-1231.</ref>; Adam 2002<ref name= "Adam">ADAM P., 2002. Salt marshes in a time of change. ''Environmental Conservation''. '''29''', 39‐61</ref>). For example, a disturbance from a [[storm surge]] can initialize this erosion process by forming a steep slope. At the disturbed edge, sediment is more vulnerable to wave action and currents. So once a cliff starts to erode, this process will not easily be stopped. Thus the steep slope remains particularly vulnerable for waves and currents until it is protected by new marsh vegetation emerging in front of the cliff. The initiation of cliff erosion is intrinsic to natural temporal salt marsh dynamics (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel">VAN DE KOPPEL J.,VAN DER WAL D., BAKKER J.P.,HERMAN P.M.J., 2005. Self‐Organization and Vegetation Collapse in Salt Marsh Ecosystems. ''The American Naturalist''. '''165''', E1-12.</ref>). However, human activities can contribute significantly to the severity of the cliff erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>). For example, shipping traffic and [[dredging]] activities can increase exposure to currents and waves, thereby increasing the pace at which lateral erosion proceeds. Moreover, human induced activities may also take away the space for natural marsh recovery in front of the eroding cliff. The latter would result in the permanent loss of a marsh.<br />
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Loss of salt marsh habitat due to lateral erosion is a major problem across the world, especially in those locations where the marsh does not seem to recover. For example, the marshes in the [[Biodiversity_and_conservation%2C_and_role_of_marine_protected_areas#Venice_Lagoon |Venice Lagoon]] (Italy) laterally erode with 1.2‐2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day">DAY J.W., SCARTON F., RISMONDO A., ARET D., 1998. Rapid Deterioration of a Salt Marsh in Venice Lagoon, Italy. ''Journal of Coastal Research''. '''14''', 583‐590.</ref>) .The estuaries of South‐East England lose about 4,000 m² <math>yr^{-1}</math> of tidal marsh area due to erosion at the seaward edges and channel widening of creeks dissecting the marsh (Hughes and Paramor, 2004<ref name= "Hughes">HUGHES R.G., PARAMOR O.A.L., 2004. On the loss of saltmarshes in south‐east England: methods for their restoration. ''Journal of Applied Ecology''. '''41''', 440‐448.</ref>). However, the main drivers of salt marsh erosion are still subject of debate (Wolters ''et al.'', 2005<ref name= "Wolters">WOLTERS M., BAKKER J.P., BERTNESS M.D., JEFFERIES R.L., MÖLLER I., 2005. Saltmarsh erosion and restoration in south-east England: squeezing the evidence requires realignment. ''Journal of Applied Ecology''. '''42''', 844‐851. </ref>). Generally, it is believed that human activities are responsible for increasing erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Pollution, shipping and dredging are some of the proposed [[anthropogenic]] causes. In addition, climate change and [[sea level rise]] receivemuch attention as a cause of salt marsh disappearance. In addition to these extrinsic forcing factors, intrinsic biological processes are also proposed (Allen, 2000<ref name= "Allen"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). For example, vegetation‐sediment feedbacks (Allen, 2000<ref name= "Allen"/>) and sediment destabilization by bioturbation and herbivory by worms (Hughes and Paramor, 2004<ref name= "Hughes"/>; van der Wal and Pye, 2004<ref name= "van der wal">VAN DER WAL D., PYE K., 2004. Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK). ''Geomorphology''. '''61''', 373‐391.</ref>) and geese (Dionne, 1985<ref>DIONNE, J.-C., 1985. Tidal marsh erosion by Geese, St. Lawrence estuary, Québec. ''Géographie physique et Quaternaire''. '''39''', 99‐105.</ref>) can also result in erosion of salt marshes. A fundamental understanding of the mechanisms that control cliff initiation and salt marsh re‐establishment in front of a cliff is needed in order to protect and manage these highly dynamic salt marsh ecosystems.<br />
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{|style="margin: 1em auto 1em auto;"<br />
|[[Image: Eroding cliff.JPG|thumb|left|300px| Figure 1: (A) Eroding cliff. (B) Patchy vegetation at pioneer zone of mudflat and saltmarsh interface. A dome-shaped patch is seen in front. (C) Salt marsh with eroding cliff separating the low marsh and pioneer zone. Pioneer vegetation (''Spartina'') has colonized the area below the eroding cliff (see also fig. 1.A). Photographs by J. van Belzen.]]<br />
|[[Image:overview of saltmarsh.JPG|thumb|none|300px| Figure 2: (A) Overview of saltmarsh by aerial photograph (RWS), comparable to situation (B.b). Cross-shoreprofile of salt‐marsh dynamics of conceptual ecomorphological model, which mimics the development of the marsh in (A). Here, (―) is the initial bare mud--‐flat profile, (―) is vegetated marsh profile at beginning, and (---) is the final profile. First, (a) saltmarsh generation due to the positive feedback between vegetation and sedimentation.Second, (b) cliff erosion of old marsh and subsequent growth at the pioneer zone (after van de Koppel, ''et al.'', 2005<ref name= "Van de Koppel"/>).]]<br />
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==VULNERABILITY & THREATS TO SALT MASRHES==<br />
===Short-term effects of flooding and storms===<br />
====SHORT-TERM FLOODING: Vulnerability of marshes to saltwater flooding====<br />
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The salt‐marsh community is well adapted to salinity due to regular tidal exposure to seawater. The vast majority of salt-marshes are well drained and therefore at less risk to the endured flooding. In comparison, the community of grazing-marshes is adapted to very dilute seawater and the habitat drainage is often slow. The potential impact of saltwater flooding is therefore more severe for [[Coastal_grazing_marsh| grazing marshes]] than for salt marshes. Much of the evidence regarding the effect of seawater on coastal vegetation therefore relates to oligohaline/grazing marshes.<br />
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====SHORT-TERM FLOODING: Effect of flooding by saline water on salt marshes ====<br />
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A flooding event that originates from increased freshwater discharge, for instance due to heavy rainfall or ice melt in a catchment area, will result in a fresh‐water pulse through downstream marshes. Unless freshwater flooding lingers for extensive periods, the impact on the vegetation of salt-and grazing- marshes will be short lived (Flynn ''et al.'', 1995<ref name= "Flynn">FLYNN, K.M.; MCKEE, .KL.; MENDELSSOHN, I.A, 1995.RECOVERY OF FRESH-WATER MARSH VEGETATION AFTER A SALTWATER INTRUSION EVENT.'' OECOLOGIA''. '''103(1)''', 63-72 DOI:10.1007/BF00328426.</ref>; Grace and Ford, 1996<ref name= "Grace">GRACE J.B., FORD M.A., 1996. The potential impact of herbivores on the susceptibility of the marsh plant ''Sagittaria lancifolia'' to saltwater intrusion in coastal wetlands. ''Estuaries''. '''19''', 13–20.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard">HOWARD R.J., MENDELSSOHN I.A., 2000. Structure and composition of oligohaline marsh plant communities exposed to salinity pulses. ''Aquat Bot''. '''68''', 143–164.</ref>). The [[Halophytic_plants|‘halophytic’]] (salt-tolerant) species that dominate salt-and grazing-marsh communities will not be harmed by short‐term fresh water exposure. However, their physiological and biochemical adaptations to cope with salinity stress make them poorly competitive under fresh water conditions (Crain ''et al., 2004''<ref name= "Crain">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549.DOI: 10.1890/03-0745 </ref>). Their halophytic traits enable them to colonise saline environments (Pennings and Callaway, 1992<ref name= "Pennings">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549. DOI: 10.1890/03-0745 </ref>). Salinity exposure in the salt marsh, and consequently the inherent salt tolerance of the inhabitant community, does not necessarily decline linearly with shore level. Summer evaporation of seawater pools can leave concentrated deposits of salt on the high marsh where the habitat is infrequently flushed, leading to high levels of sediment salinity that exclude less halophytic species (Watson and Burne, 2009). Paradoxically, increased frequency of seawater flushing by storms might dilute the accrued sediment salinity of such high marsh environments and alter the zonation of species. For instance, increased tidal flooding of an elevated marsh plain can cause the normally very halophytic high marsh species to be replaced by salt‐intolerant lower shore species (Watson and Burne, 2009).<br />
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The severity of impact of salt water flowing is likely to depend on the natural salinity occurring at a specific location. Relatively brackish-marshes, dominated by halophytic plants, will see less changes to community composition than fresh water dominated grazing marshes and coastal flood plains (Brown ''et al.'', 1994). Increased flooding by salt water is most likely to have the greatest effect on the fresh‐water adapted members of the marsh vegetation (Crain ''et al.'', 2004<ref name= "Crain"/>), which increases in dominance in the transitional and grazing‐marsh above the tidal marks. Stormy conditions that result in a temporary increase in sea level and which bring in salt water pulses to coastal marsh systems therefore should have a greater effect on the grazing‐marsh community than on the salt marsh community. For example, seawater flooding of a diked grazing-marsh, following a dike breaching, prevented most of the fresh water vegetation from developing in the following spring (Klein and Bateman, 1998<ref name= "Klein">KLEIN R.J.T., BATEMAN I.J., 1998. The recreational value of Cley marshes nature reserve: An argument against managed Retreat? ''Water and Environment Journal''. '''12''', 280-285. </ref>). Vegetation cover, species richness, recovery and re-establishment of an oligohaline marsh decreased during one month of experimental exposures to increased salinity (from 0.5‐5.0 salinity up to 12) (Howard and Mendelssohn, 2000<ref name= "Howard"/>). In the longer term, the space left by dead vegetation is likely to be colonised by more salinity tolerant species, and thus grazing-marsh communities might come to resemble those of salt marshes (Doody, 1982<ref name= "Doody">DOODY J.P., 1982. Sea defence and nature conservation: threat or opportunity. ''Aquat Conserv Mar Freshw Ecosyst'', '''2''', 275-283.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard"/>).<br />
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Many coastal marsh plants are able to recover temporary increases in salinity (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Grace and Ford, 1996<ref name= "Grace"/>; Howard and Mendelssohn, 2000<ref name= "Howard"/>). However, the potential for lasting changes to communities increases with the duration of flooding (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Howard and Mendelssohn 2000<ref name= "Howard"/>). Elevated salinity (from natural, 0.5‐5 to 15) slowed vegetation recovery more in flooded than in drained soils (Flynn ''et al.'', 1995<ref name= "Flynn"/>). The naturally slow drainage of grazing marshes, that follows temporary sea water flood, causes this habitat to remain immersed for longer periods than salt marshes. Grazing marshes are therefore at greater risk to the endured flooding. However, there are indications that these marshes are relatively resilient to exposure; if the water is brackish enough, it may require months of immersion before significant impacts to vegetation cover occurs (e.g. Howard and Mendelssohn, 2000<ref name= "Howard"/>). Brewer and Grace (1990)<ref>BREWER J.S., GRACE J.B., 1990. Plant community structure in an oligohaline tidal marsh. ''Vegetatio''. '''90''', 93–107.</ref> hypothesized that occasional storm‐generated pulses of salt water moving into an oligohaline marsh would generate short-lived salinity gradients that, along with biotic interactions, would regulate species distributions over longer terms. Sharpe and Balwin (2009)<ref name= "Sharpe">SHARPE P. J., BALWIN A.H., 2009. Patterns of Wetland Plant Species Richness Across Estuarine Gradients of Chesapeake Bay. ''Wetlands''. '''29''', 225-235.</ref> proposed that an unexpected peak in vegetation species richness in the transitional marsh arose because pulsed variation in salinity (0‐5) prevented domination by fresh water or salt water species. Thus, pulsed salinity exposure might not necessarily diminish vegetation diversity. Nevertheless, increased salt water flooding of grazing marshes is likely to drive the succession towards more salt-tolerant vegetation, and increase the resemblance with salt marsh assemblages. Note that the empirical evidence for the rate of this transition is lacking (Nicholls and Wilson, 2001<ref name= "Nicholls">NICHOLLS R.J., WILSON T., 2001. Chapter five. Integrated impacts on coastal areas and river flooding. In: Holman I.P., Loveland P.J. (Eds), Regional Climate Change Impact and Response Studies in East Anglia and North West England (RegIS). Final Report of MAFF project no. CC0337. (downloadable at [http://www.ukcip.org.uk www.ukcip.org.uk]).</ref>). The consequence of increased coastal flooding might therefore be a gradual loss of grazing-marsh communities, in exchange for gain in area cover of salt marsh communities (Doody, 1982<ref name= "Doody"/>; Klein and Bateman, 1998<ref name= "Klein"/>; Nicholls and Wilson, 2001<ref name= "Nicholls"/>). <br />
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====SHORT-TERM FLOODING: Interactions of salinity with other disturbances ====<br />
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It is important to caution against a general interpretation that seawater flooding is a minimal risk to coastal marshes in general. The severity of seawater influence on grazing‐marshes might depend much on whether the salinity is paralleled with other plant stressors and disturbances. Sharpe and Balwin (2009)<ref name= "Sharpe"/> sampled plant diversity in a marsh in the United States, across a fresh (salinity 0.5) to mesohaline (5-18) salinity gradient. In an undisturbed marsh, richness in transition zone oligohaline marshes was as high as or higher than in tidal fresh water-marshesIn an anthropogenically disturbed estuary, however, plant species richness declined linearly with an increase in salinity. Experimental flooding by brackish (6‐14) water had a greater effect on grazing‐marsh community structure and [[biomass]] when the vegetation was also disturbed by leaf clipping (Baldwin and Mendelssohn, 1998) or grazing (Gough and Grace, 1998). In comparison, flooding did not affect species richness in the absence of such additional disturbances (Baldwin and Mendelssohn, 1998). If the salinity and water regimes are permanently altered and/or the vegetation is destroyed by a combination of factors, the substrate might eventually subside. Substrate [[Natural_causes_of_coastal_erosion#Subsidence |subsidence]] and associated increased water depth might prevent seed dispersal and germination of more flooding tolerant species, and thus hamper system recovery (McKee and Mendelssohn, 1989<ref name= "Mckee en M">MCKEE K.L.; MENDELSSOHN I.A.,1989. Response of a fresh-water marsh plant community to increased salinity and increased water level. ''AQUATIC BOTANY''. '''34(4)''', 301-316. DOI: 10.1016/0304-3770(89)90074-0.</ref>).It is not known beyond which threshold the frequency of flooding will have permanent effects.<br />
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====SHORT-TERM: Vulnerability of marshes to storm damage====<br />
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As mentioned above, flooding can induce some disturbances to the vegetation composition of salt marshes. However, the threat storms impose on salt marshes is more likely to result from storm-associated damage than from flooding. Wind-induced waves can destabilize sediments, initiate and propagate lateral cliff erosion, tear of plant material, as well as deposits of wrack and debris in marshes. The [[vulnerability]] of salt marshes is largely related to the effects of waves on sediment stability and on lateral erosion. The evidence we present for the effects of storm associated erosion mostly originates from salt marshes seeing as the literature on grazing-marsh damage from salt water erosion is scarce. Severe salt marsh erosion will undoubtedly lead to an increased risk of sea water flooding and storm-associated damage for adjoined grazing‐marshes, and might eventually drive a transition of grazing‐marsh communities into salt marsh habitats.<br />
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====SHORT-TERM STORM: Sediment destabilization and lateral erosion of salt marshes====<br />
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Storm events can induce sediment stabilization and lateral erosion, which can have an important impact on the dynamics and functioning of salt marshes. Although lateral erosion is an intrinsic process for salt marshes and part of the natural cyclic behaviour, it generally gets initiated by a storm (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Such cyclic behaviour requires sufficient space for marshes to migrate landward. This space is nowadays being diminished due to anthropogenic land use. Hence, the lateral erosion of salt marshes has become a global threat, as it is unclear under which conditions an eroding marsh can re‐establish in the limited available space. For example, the marshes in the Venice Lagoon (Italy) erode 1.2-2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day"/>) and estuaries of South-East England lose ~4,000 m² of tidal marsh per annum from erosion at the seaward edges and widening of creeks within the marsh (Hughes and Paramor, 2004<ref name= "Hughes"/>). In these locations, large areas of marsh are lost due to cliff erosion with little or no recovery of the vegetation. <br />
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It is clear that storms contribute significantly to the loss by lateral erosion. However, the main driving factors initiating this erosion are still not clear (Wolters ''et al.'', 2005<ref name= "Wolters"/>). Human activities can be, in part, responsible for increasing erosion rates through [[pollutant]]-driven diminishing of vegetation cover and/or by enhancing hydrodynamic energy reaching the marsh via ship waves and channel dredging (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Thus, there is a strong need for a fundamental understanding of the cyclic functioning of salt marsh ecosystems in order to understand when disturbances by storms will start a natural cycle of rejuvenation versus when they cause the irreversible loss of a marsh and thus would benefit from protective measures. <br />
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Vulnerability of the saltmarsh to the initiation of cliff erosion will largely depend on the age of the marsh. Cliff erosion is hypothesized to be an inevitable and intrinsic consequence of the ecomorphological dynamics of saltmarshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). That is, the capture of sediment by the vegetation leads to vertical salt marsh growth, which in the long term makes the salt marsh susceptible to lateral erosion (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). Both conceptual modelling and empirical evidence showed that a positive feedback between vegetation growth and sediment capture generates an increasingly steeper bank at the seaward edge of the marsh (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). As a consequence, salt‐marsh edges become more vulnerable to disturbance as they mature (see Figure 1.B). This means that in the end, relatively small disturbances like from minor storm events or ship waves may induce the erosion. Data on sedimentation in salt-marshes, obtained from sediment core transects and spatiotemporal analysis of aerial photographs, support this conceptual model (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal">VAN DER WAL D., WIELEMAKER-VANDENDOOL A., HERMANP.M.J., 2008. Spatial patterns, rates and mechanisms of saltmarsh cycles (Westerschelde, The Netherlands). ''Estuarine, Coastal and Shelf Science''. '''76''', 357‐368. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=143078 www.vliz.be/imis].</ref>), suggesting that, in a wide range of circumstances, lateral retreat due to cliff erosion will happen sooner or later. <br />
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[[Resilience]] of the marsh edge to erosion will depend on the interplay between vegetation composition and sediment dynamics. For instance, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina]'' plants reduce cliff erosion more than ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=232101 Limonium]'' plants do due to differences in their root system. As a consequence, a ''Spartina'' dominated marsh edge is likely less vulnerable to storm events (van Eerdt, 1985). However, consequences of plant community on the vulnerability and resilience of the marsh can be more complex. The above ground plant traits can have other effects on the vegetation-sediment interaction. For example, stiffness and density of the plant may affect sedimentation rates (Bouma ''et al.'', 2005<ref name= "Bouma05"/>, 2009, 2010). The overall effect of above and below plant traits on salt‐marsh resilience/vulnerability remains largely unknown and subject to ongoing research. <br />
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Alongside cliff erosion, re‐growth of pioneer vegetation on the cleared mudflat in front of the saltmarsh cliff ideally occurs, thereby rejuvenating the mature marsh (see Figure.1.B; van de Koppel, ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>). This pioneer vegetation determines the conditions for lateral retreat and gradually slows down erosion of the salt-marsh edge. <br />
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The establishment of pioneer vegetation is therefore of vital importance for the development and recovery of salt marshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>; Callaghan ''et al.'', 2010<ref name= "callaghan">CALLAGHAN, D.P.; BOUMA, T.J.; KLAASSEN, P.; VAN DER WAL, D.; STIVE, M.J.F.; HERMAN, P.M.J., 2010. Hydrodynamic forcing on salt-marsh development: Distinguishing the relative importance of waves and tidal flows Est., ''Coast. and Shelf Sci.''. '''89(1)''', 73-88. dx.doi.org/10.1016/j.ecss.2010.05.013. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=206900 www.vliz.be/imis].</ref>). This emphasizes the importance of initial conditions for the establishment and growth of vegetation, and the physical conditions that may constrain these intrinsic processes for salt marsh development (van der Wal ''et al.'', 2008<ref name= "VdWal"/>). However, the factors limiting seedling establishment remain poorly understood (Bouma ''et al.'', 2009). We hypothesize that sediment destabilization plays a critical role in the ability for pioneer establishment on a mudflat and, therefore, in the ability of the salt marsh to recover from lateral cliff erosion (Balke ''et al.'', submitted; Bouma ''et al.'', submitted; van Belzen ''et al.'', in prep a; Infantes ''et al.'', submitted). <br />
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====SHORT-TERM STORM: sediment and wrack deposits on salt marshes====<br />
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Depositions of wrack, debris or large amounts of sediment, associated with extreme flooding events, can have significant effects on salt marsh vegetation. Wrack depositions may smother less hardy vegetation, leaving bare patches and opportunity for new colonization by neighbouring species, or from dispersed seeds (Bertness and Ellison, 1987<ref>BERTNESS M.D., ELLISON A.M., 1987. Determination of pattern in a New England salt marsh plant community. ''Ecol Monogr''. '''57''', 129‐14.</ref>; Tolley and Christian, 1999<ref name= "Tolley">TOLLEY P.M.; CHRISTIAN R.R., 1999. Effects of increased inundation and wrack deposition on a high salt marsh plant community. ''ESTUARIES''. '''22(4)''', 944-954.DOI: 10.2307/1353074.</ref>). Large algal mats can have residence times of 3‐4 months (Valiela and Rietsma, 1995<ref name= "Valiella">VALIELA I.; RIETSMA C.S.,1995. DISTURBANCE OF SALT-MARSH VEGETATION BY WRACK MATS IN GREAT-SIPPEWISSETT-MARSH. ''OECOLOGIA''. '''102(1)''', 106-112. </ref>). While wrack depositions may not be as significant in cover (Valiela and Rietsma, 1995<ref name= "Valiella"/>), small-scale alteration in species cover by algal wrack depositions does have the potential for wider effects on community diversity if the same spots are regularly covered by seaweed (van Hulzen ''et al.'', 2006<ref name= "van Hulzen"/>). The deposition of sediments following storm flooding may be significant. Experimental flooding and sedimentation of seedbanks of an oligohaline marsh community showed that an addition of 2 cm of sediment decreased plant density and germination of seedlings, suggesting that an increase in sedimentation and relative sea level may reduce plant biodiversity (Peterson and Baldwin, 2004<ref>PETERSON J.E., BALDWIN A.H., 2004. Seedling emergence from seed banks of tidal freshwater wetlands: response to inundation and sedimentation. ''Aquat Bot''. '''78,''' 243–254. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=59970 www.vliz.be/imis].</ref>]). The deposition of sediments might be positive for subducting and nutrient starved marshes. For example, within a year after 3-8 cm of sediment deposited by Hurricane Katrina, the vegetation of a high marsh had fully recovered and below‐ground root growth had increased 10‐fold (McKee and Cherry, 2009<ref name= "Cherry">MCKEE K.L., CHERRY J.A., 2009. Hurricane Katrina sediment slowed elevation loss in subsiding brackish marshes of the Mississippi river delta. ''Wetlands''. '''29''', 2-15.</ref>).<br />
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While single factors may have limited effects on marshes, a collective of concurrent stressors is likely to generate significant impacts on marsh communities. The deposition of wrack and sediments is often concurrent with other habitat stressors that might jointly influence marsh vegetation cover. Thus, while Tolley and Christian (1999)<ref name= "Tolley"/> found little effect of sea water flooding on vegetation biomass, the simultaneous deposition of algal wrack greatly repressed plant cover and biomass, in some species irreversibly so.<br />
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===Long-term effects due to climate change and sea level rise===<br />
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[[Coastal squeeze]], due to sea level rise, and erosion are primary threats to salt marshes across Europe. They can result in reduced coastal defence value and in an increased risk of flooding. Although sea level rise may pose serious threats to the survival of salt marshes, there is growing evidence that as long as sediment supply is sufficient, the vegetation-sedimentation feedback of marshes enables marshes to accrete vertically at the rate of the rising sea-level (Kirwan and Temmerman, 2009<ref name= "KenT">KIRWAN M., TEMMERMAN S., 2009. Coastal marsh response to historical and future sea-level acceleration. ''Quaternary Science Reviews''. '''28''', 1801-1808.</ref>). However, if the suspended matter load is reduced by climate change or by significant human alteration in a catchment area, vegetation- sedimentation feedbacks can become limited, affecting the potential of marshes to accrete (Kirwan and Temmerman, 2009<ref name= "KenT"/>). As explained in the previous sections, lateral marsh erosion can become a serious threat to salt marshes over time if seedling establishment in front of the marsh is not possible so that re- growth of the marsh is prevented. Many aspects that affect the cyclic dynamics of marshes are still not well understood. Important in maintaining the vegetation-sedimentation feedback is that the sedimentary conditions remain more or less the same.<br />
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Several managerial aspects are likely to compromise the capacity for marshes to persist and to protect the coast. Reduction in area by coastal squeeze will reduce the wave attenuation capacity, as the efficiency of energy reduction is strongly dependent on the depth of the marsh (Möller, 2006<ref name= "Moller">MÖLLER I., 2006. Quantifying saltmarsh vegetation and its effect on wave height dissipation: Results from a UK East coast saltmarsh. ''Estuarine Coastal and Shelf Science''. '''69''', 337‐351.</ref>). Whether this might have negative feedback on marsh accretion and accelerate area loss is not known. Effects of grazing might also reduce the vegetation‐sedimentation feedback by reducing vegetation cover and height, thereby hampering the development of salt marshes (Kiehl ''et al.'', 2007<ref name= "Kiehl07">KIEHL K., SCHRÖDER H., STOCK M., 2007. Long‐term vegetation dynamics after land‐use change in Wadden Sea salt marshes. ''Coastline Reports''. '''7''', 17‐24.</ref>). Finally, very little is known about the implications on salt marsh resilience from interactions between different environmental, climatic and managerial variables. Interactions between climate stressors (e.g. desiccation, irradiation), physical forcing (extreme flooding events, increased storminess) and environmental management (eutrophication, grazing, and managed retreat) will be a likely reality for many marshes. This is important because interactive stresses can be synergistic and cause shifts in the stable states of ecosystems, which can compromise the naturally delivered services (Scheffer ''et al.'', 2001<ref>SCHEFFER M., CARPENTER S., FOLEY J.A., FOLKER C., WALKER B., 2001. Catastrophic shifts in ecosystems. ''Nature''. '''413''': 591‐596. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=19763 www.vliz.be/imis].</ref>; Scheffer ''et al.'', 2009<ref>SCHEFFER M., BASCOMPTE J.,BROCK W. A., BROVKIN V., CARPENTER S., DAKOS V.,HELD H., VANNESE.H., RIETKERK M., SUGIHARA G., 2009. Early-warning signals for critical transitions. ''Nature''. '''461''', 53‐59. </ref>). Our evaluation of the resilience of salt marshes to disturbance, including climate change, might for the time being still be somewhat naïve and based on limited current research. <br />
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[[Image: Chongming Dongtan.JPG|thumb|right|250px|Figure 3: Impact of sea-level rise on tidal flat and tidal marsh complex by 2050 (a and b) and 2100 (c and d) year at Chongming Dongtan nature reserve.]]<br />
====CASE STUDY: FORECASTING THE EFFECTS OF SEA‐LEVEL RISE====<br />
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Located at the mouth of the Yangtze Estuary, the Chongming Dongtan nature reserve is extremely vulnerable to climate change and especially to an accelerated sea-level rise. We use a variety of data from [[remote sensing]], an in situ global positioning system (GPS), tidal gauges, nautical charts, geographic spatial analysis modelling gand IPCC sea-level rise scenarios to forecast the potential impacts of increased sea level on the coastal wetland habitat of the Chongming Dongtan Nature Reserve (Figure 3). The results indicate that around 40% of the intertidal zone of the nature reserve will be inundated by the year 2100 due to an estimated 0.88 m increase in sea level (Figure 3.c and 3.d). In particular, the ''Scirpus mariqueter'' communities and bare tidal flats are more vulnerable to sea‐level rise. The identification, mapping and statistical summary of environmental impacts of the projected sea-level rise at Chongming Dongtan Nature Reserve represent an important initial step for decision makers concerned with mitigation of the adverse impacts of sea-level rise. In this study, the inundation‐based assessment was developed to inform policymakers, managers and the public about the amount and the spatial distribution of tidal wetland change as a result of sea‐level rise. The results indicate that the zones most vulnerable to sea-level rise at the Chongming Dongtan Nature Reserve is the ''S. Mariqueter'' zone, the bare tidal flat zone and the tidal creeks, which are the most suitable habitats for migratory birds. A ~30% loss of the ''S. Mariqueter'' marsh community by the year 2100 would eliminate a rich invertebrate food source and cause deterioration in the estuarine food web for migrating birds; such a loss could arise from human-induced stressors such as land reclamation, seawall constructions, overfishing and local pollution. As tidal marshes and flats submerge and decline in size and productivity, increased crowding in the remaining areas could lead to reductions in and eventually even exclusion of some local shorebird populations (Tian ''et al.'', 2010<ref>TIAN, B; ZHANG, LQ ; WANG, XR; ZHOU, YX ; ZHANG, W.; 2010. Forecasting the effects of sea-level rise at Chongming Dongtan Nature Reserve in the Yangtze Delta, Shanghai, China. ''ECOLOGICALENGINEERING'', '''36(10)''': 1383-1388.DOI: 10.1016/j.ecoleng.2010.06.016.</ref>). <br />
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==KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY ==<br />
===Effects of single disturbance events on marsh responses to long-term change===<br />
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Single events, such as violent storms, normally have short-lived effects on the species composition and on the ecological functioning of salt-marshes (Flynn ''et al.'' 1995<ref name= "Flynn"/>, Howard and Mendelssohn, 2000<ref name= "Howard"/>; McKee and Cherry, 2009<ref name= "Cherry"/>), and are thus of less importance compared to long term persistent changes in environmental condition. Long-term processes of coastal squeeze with sea level rise and lateral erosion with increased storminess are considered to be the primary threats to salt- and grazing-marshes across Europe (Nicholls and Wilson, 2001<ref name= "Nicholls"/>. A single storm can push a marsh over the tipping point, shifting it from laterally expanding towards laterally eroding. If erosion persists, and the marsh cannot re-establish in front of the cliff, in time this will result in reduced coastal defence value and an increased risk of flooding of adjacent terrestrial environment (e.g. grazing- marshes) (Klein and Bateman, 2007).<br />
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==CURRENT MANAGEMENT PRACTICES==<br />
===Making space for water===<br />
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Currently, salt-marshes are managed extensively because of their acknowledged role in coastal protection. Many countries like e.g. the UK, the Netherlands, etc, have developed management schemes in order to make space for water along river flood plains, estuarine and coastal areas (Bakker, ''et al.'', 2005; DEFRA, 2004). This way, river run‐off and occasional high sea water levels can be attenuated by the natural buffer and retention capacity of the landscape. For example, restoring the water storage volume in an estuary can reduce the tidal prism, smoothing the tidal amplitude, which reduces the risk of flooding in up-stream estuarine areas. Salt‐marshes play an important part in this contemporary policy, because creating new marsh‐land both increases tidal water storage in up‐stream estuarine areas and wave attenuation of storm surges along exposed coast lines (Bakker ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>).<br />
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===Managed retreat/realignment and salt-marsh engineering===<br />
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The current effort to restore marsh systems in Europe and elsewhere represents graphic evidence of the political and managerial value placed on the goods and services provided by this ecosystem. The principle of ‘managed realignment’ and ‘managed retreat’ comes down to allowing salt-marsh areas, that were historically converted to alternative use for anthropogenic purposes (e.g. agricultural land or tourist development), to return to their natural state and area cover (Garbutt, ''et al.'', 2006<ref>GARBUTT, R.A.; READING, C.J.; WOLTERS, M.; GRAY, A.J.; ROTHERY, P., 2006. Monitoring the development of intertidal habitats on former agricultural land after the managed realignment of coastal defences at Tollesbury, Essex, UK. ''MARINE POLLUTION BULLETIN''. '''53(1-4)''', 155-164. DOI: 10.1016/j.marpolbul.2005.09.015.</ref>). This can be done in a number of ways, but typically involves making a breach in the historically erected barrier (seawall, dike) rather than removing the whole structure. This approach reduces the costs involved, as well as the wave action depressing the development of the vegetation. Cost benefit analyses typically show a net advantage of managed realignment over other constructed defence options (Turner, ''et al.'', 2007<ref>TURNER, R.K.; BURGESS, D .; HADLEY, D.; COOMBES, E.; JACKSON, N.; 2007. A cost-benefit appraisal of coastal managed realignment policy. ''GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS''. '''17(3-4)''': 397-407.DOI: 10.1016/j.gloenvcha.2007.05.006.</ref>). Full restoration of natural ecosystem function has met some complications. The substrates and biodiversity of pristine salt marshes is often markedly different from an artificial or restored system, even 100 years after natural processes have been allowed to operate (Hazelden and Boorman, 2001<ref>HAZELDEN J.; BOORMAN L.A.; 2001.Soils and 'managed retreat' in South East England.''SOIL USE AND MANAGEMENT''. '''17(3)''':150-154. DOI: 10.1079/SUM200166.</ref>). The implications of this managed realignment on coastal protection by marshes are not known. The MOSE project of the Venice lagoon is an impressive example of large-scale engineering to create salt‐marsh wetlands, largely for their role in dampening wave action and erosion within the lagoon (MOSE 2010).<br />
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===Grazing management and coastal protection===<br />
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There is evidence to suggest that grazing management could be of particular importance to the capacity of marshes for protecting the coast, although there has been little quantitative research on this subject (Bakker, ''et al.'', 2005). The vegetation is of key importance to coastal protection by marshes, through consolidation of the soil and by representing a structural hindrance to wash-over waves. Evidently, livestock has large potential for altering the vegetation structure directly through feeding and indirectly by altering the conditions for vegetation growth (Bakker, ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>). Feeding and defecation moderate vegetation structure‐composition and above- and below-ground biomass production. Trampling and hoof holes lead to soil compaction and can cause saltpan formation (Vera, 2000<ref>VERA F.W.M., 2000. Grazing Ecology and Forest History. CABI Publishing, Wallingford, UK.</ref>). The potential of management of grazing regime to influence the salt marsh coastal protection potential is therefore high. Intense grazing modifies zonation patterns and transforms complex communities with woody species into homogenous lawns dominated by short flexible grass (Andresen, ''et al.'', 1990<ref name= "Andersen">ANDRESEN H., BAKKER J.P., BRONGERS M., HEYDEMANN B., IRMLER U., 1990. Long‐term changes of salt-marsh communities by cattle grazing. ''Vegetatio''. '''89''', 137–148.</ref>; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>), with an associated likely reduction in wave attenuation (Möller, 2006<ref name= "Moller"/>) and sedimentation rates (Andresen, ''et al.'', 1990<ref name= "Andersen"/>). Grazing at low intensity increases vegetation patchiness and biodiversity due to selective grazing of palatable species (Bakker, 1985<ref>BAKKER J. P., DIJKSTRA M., RUSSCHEN P. T., 1985. Dispersa, germination and early establishment of halophytes and glycophytes on a grazed and abandoned salt‐marsh gradient. ''New Phytologist''. '''101''', 291-308.</ref>, 1998; Kiehl ''et al.'', 1996<ref>KIEHL K., EISCHEID I., GETTNER S., WALTER J., 1996. Impact of different sheep grazing intensities on salt-marsh vegetation in northern Germany. ''Journal of Vegetation Science''. '''7''', 99–106.</ref>; Adler ''et al.'', 2001<ref>ADLER P.B.; RAFF D.A.; LAUENROTH W.K.;, 2001.The effect of grazing on the spatial heterogeneity of vegetation. ''OECOLOGIA''. '''128(4)''': 465-479.</ref>; Bouchard ''et al.'', 2003<ref>BOUCHARD V.; TESSIER M.; DIGAIRE F.; VIVIER, J.P.; VALERY, L.; GLOAGUEN, J.C.; LEFEUVRE, J.C., 2003. Sheep grazing as management tool in Western European saltmarshes.InternationalCongress on Biodiversity Conservation and Management. ''COMPTES RENDUS BIOLOGIES''. '''326''', S148-S157.DOI: 10.1016/S1631-0691(03)00052-0.</ref>; Marriot ''et al.'' 2005). Patchiness may cause specific spatial patterns in turbulence and sedimentation (Boorman, 1999; van Wesenbeeck, ''et al.'', 2007), so that the sum effect of patchiness on marsh coastal protection is not known. Conversely, grazing pressure can lead to greater resource allocation of below‐ground biomass (Pucheta, ''et al.'', 2004<ref>PUCHETA, E.; BONAMICI, I.; CABIDO, M.; DIAZ, S.; 2004. Below-ground biomass and productivity of a grazed site and a neighbouring ungrazed exclosure in a grassland in central Argentina. ''AUSTRALECOLOGY''. '''29(2)''', 201-208.DOI: 10.1111/j.1442-9993.2004.01337.x. </ref>), thus reducing surface erosion and below-ground contributions to an increase in marsh surface elevation. <br />
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==see also==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Salt_marshes |Salt marshes]]<br />
<br />
[[Natural_barriers#Salt_marshes | Natural barriers, salt marshes]]<br />
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[[Salt_marches_in_Europe_and_temporal_variability |Salt marches in Europe and temporal variability]]<br />
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</br><br />
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==References==<br />
<references/></br><br />
<br />
[[Category: Salt marshes ]]<br />
[[Category: Coastal erosion ]]<br />
[[Category: Biodiversity and habitat loss]]<br />
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{{ 5Authors<br />
|AuthorID1=25081<br />
|AuthorFullName1= van Belzen, Jim<br />
|AuthorID2=8361<br />
|AuthorFullName2= Bouma, Tjeerd<br />
|AuthorID3=20719<br />
|AuthorFullName3= Skov, Martin<br />
|AuthorID4=20751<br />
|AuthorFullName4= Zhang, Liquan<br />
|AuthorID5=?<br />
|AuthorFullName5= Yuan, Lin<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_salt_marshes&diff=50214Dynamics, threats and management of salt marshes2012-07-24T13:24:50Z<p>Katreineblomme: </p>
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<div>__TOC__<br />
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==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
<br />
Coastal areas, like [[estuaries]], are high energetic environments where organisms are exposed to hydrodynamic forces from waves and tidal [[currents]]. Ecosystem engineering species (Jones ''et al.'', 1997) play an important role in shaping the [[intertidal]] landscape (Temmerman ''et al.'', 2007<ref name= "Temmerman">TEMMERMAN, S.; BOUMA, T.J.; VAN DE KOPPEL, J.; VAN DER WAL, D.; DE VRIES, M.B.; HERMAN, P.M.J.(2007). Vegetation causes channel erosion in a tidal landscape. ''Geology''. '''35(7)''', 631-634. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=114118 www.vliz.be/imis]</ref>; Weerman ''et al.'', 2010). Coastal vegetation, like [[salt marsh]] vegetation, are ecosystem engineers in that they can strongly attenuate hydrodynamic energy from tidal current and [[waves]] (Bouma ''et al.'', 2005<ref name= "Bouma05">BOUMAT.J.,DE VRIES M.B., LOW E., PERALTA G., TNCZOSI.C.,VANDEKOPPELJ., HERMAN P. M. J., 2005. Trade‐offs Related to Ecosystem Engineering: A Case Study on Stiffness of Emerging Macrophytes. ''Ecology''. '''86''', 2187‐2199.</ref>, 2007<ref name= "Bouam07">BOUMA, T.J.; VAN DUREN, L.A.; TEMMERMAN, S.; CLAVERIE, T.; BLANCO-GARCIA, A.; YSEBAERT, T.J.; HERMAN, P.M.J. (2007). Spatial flow and sedimentation patterns within patches of epibenthic structures. ''Cont. Shelf Res.''. '''27(8)''': 1020-1045. dx.doi.org/10.1016/j.csr.2005.12.019<br />
Available from:[http://www.vliz.be/imis/imis.php?module=ref&refid=114437 www.vliz.be/imis]</ref>, 2010). This has a positive effect on sediment accretion rates, and hence results in increased sediment elevation. In turn, increased sediment elevation stimulates plant growth because the inundation duration for the vegetation is shortened. This results in positive feedbacks between plant growth and sediment accretion. Implications of this feedback can be observed in the field in the form of dome shaped hummocks of cord‐grass (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina spp.]''). They can be found on the [[Tidal flats from space|mud flats]] seaward of the salt marsh edge (Figure 1), where the salt marsh is developing.<br />
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Feedbacks between hydrodynamic forces, sediment accretion and vegetation are key processes in shaping salt marshes (Temmerman ''et al.'', 2007<ref name= "Temmerman"/>; van Wesenbeeck ''et al.'', 2008). Locally the canopy of a vegetation stand can attenuate currents and waves which result in a net [[sedimentation]]. However, the same canopy also obstructs the flow, thereby diverting it and increasing flow velocities in the areas adjacent to the canopy because of conservation of mass and energy (Bouma ''et al.'', 2009). This biomechanical stress diversion can result in negative feedbacks on vegetation settlement and growth at some distance from the canopy (van Wesenbeeck ''et al.'', 2008). However, the outcome of these feedbacks may be dependent on the local context, seeing as these kinds of feedbacks are density‐dependent (Bouma ''et al.'', 2009). In other words, the strength of these negative feedbacks may vary with vegetation age, composition, or even the sediment type it is growing in (van Hulzen ''et al.'', 2006<ref name= "van Hulzen">VAN HULZEN J.,VAN SOELEN J.,HERMAN P.M.J., BOUMA T.J., 2006.The significance of spatial andtemporal patterns of algal mat deposition in structuring salt marsh vegetation. ''J Veget Sci.''. '''17''', 291‐298.</ref>). Overall these feedbacks cause complex patterns of gullies and hummocks until eventually a mature marsh arises, dissected by a complex drainage system (Kirwan and Murray, 2007; Temmerman ''et al.'', 2007<ref name= "Temmerman"/>).<br />
<br />
Many marshes are characterized by a cyclic nature, where marsh formation is followed by destruction (Figure 2). After a period of lateral extension, large scale lateral erosion of salt marshes can set in when the marsh edge becomes disturbed, a phenomenon often referred to as cliff erosion (see Figure 1.a, Figure 2.B.b; Allen, 2000<ref name= "Allen">ALLEN J.R.L., 2000. Morphodynamics of Holocene salt marshes: a review sketch from the Atlantic and Southern North Sea coasts of Europe. ''Quaternary Science Reviews''. '''19''', 1155-1231.</ref>; Adam 2002<ref name= "Adam">ADAM P., 2002. Salt marshes in a time of change. ''Environmental Conservation''. '''29''', 39‐61</ref>). For example, a disturbance from a [[storm surge]] can initialize this erosion process by forming a steep slope. At the disturbed edge, sediment is more vulnerable to wave action and currents. So once a cliff starts to erode, this process will not easily be stopped. Thus the steep slope remains particularly vulnerable for waves and currents until it is protected by new marsh vegetation emerging in front of the cliff. The initiation of cliff erosion is intrinsic to natural temporal salt marsh dynamics (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel">VAN DE KOPPEL J.,VAN DER WAL D., BAKKER J.P.,HERMAN P.M.J., 2005. Self‐Organization and Vegetation Collapse in Salt Marsh Ecosystems. ''The American Naturalist''. '''165''', E1-12.</ref>). However, human activities can contribute significantly to the severity of the cliff erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>). For example, shipping traffic and [[dredging]] activities can increase exposure to currents and waves, thereby increasing the pace at which lateral erosion proceeds. Moreover, human induced activities may also take away the space for natural marsh recovery in front of the eroding cliff. The latter would result in the permanent loss of a marsh.<br />
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Loss of salt marsh habitat due to lateral erosion is a major problem across the world, especially in those locations where the marsh does not seem to recover. For example, the marshes in the [[Biodiversity_and_conservation%2C_and_role_of_marine_protected_areas#Venice_Lagoon |Venice Lagoon]] (Italy) laterally erode with 1.2‐2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day">DAY J.W., SCARTON F., RISMONDO A., ARET D., 1998. Rapid Deterioration of a Salt Marsh in Venice Lagoon, Italy. ''Journal of Coastal Research''. '''14''', 583‐590.</ref>) .The estuaries of South‐East England lose about 4,000 m² <math>yr^{-1}</math> of tidal marsh area due to erosion at the seaward edges and channel widening of creeks dissecting the marsh (Hughes and Paramor, 2004<ref name= "Hughes">HUGHES R.G., PARAMOR O.A.L., 2004. On the loss of saltmarshes in south‐east England: methods for their restoration. ''Journal of Applied Ecology''. '''41''', 440‐448.</ref>). However, the main drivers of salt marsh erosion are still subject of debate (Wolters ''et al.'', 2005<ref name= "Wolters">WOLTERS M., BAKKER J.P., BERTNESS M.D., JEFFERIES R.L., MÖLLER I., 2005. Saltmarsh erosion and restoration in south-east England: squeezing the evidence requires realignment. ''Journal of Applied Ecology''. '''42''', 844‐851. </ref>). Generally, it is believed that human activities are responsible for increasing erosion (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Pollution, shipping and dredging are some of the proposed [[anthropogenic]] causes. In addition, climate change and [[sea level rise]] receivemuch attention as a cause of salt marsh disappearance. In addition to these extrinsic forcing factors, intrinsic biological processes are also proposed (Allen, 2000<ref name= "Allen"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). For example, vegetation‐sediment feedbacks (Allen, 2000<ref name= "Allen"/>) and sediment destabilization by bioturbation and herbivory by worms (Hughes and Paramor, 2004<ref name= "Hughes"/>; van der Wal and Pye, 2004<ref name= "van der wal">VAN DER WAL D., PYE K., 2004. Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK). ''Geomorphology''. '''61''', 373‐391.</ref>) and geese (Dionne, 1985<ref>DIONNE, J.-C., 1985. Tidal marsh erosion by Geese, St. Lawrence estuary, Québec. ''Géographie physique et Quaternaire''. '''39''', 99‐105.</ref>) can also result in erosion of salt marshes. A fundamental understanding of the mechanisms that control cliff initiation and salt marsh re‐establishment in front of a cliff is needed in order to protect and manage these highly dynamic salt marsh ecosystems.<br />
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</br><br />
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[[Image: Eroding cliff.JPG|thumb|left|300px| Figure 1: (A) Eroding cliff. (B) Patchy vegetation at pioneer zone of mudflat and saltmarsh interface. A dome-shaped patch is seen in front. (C) Salt marsh with eroding cliff separating the low marsh and pioneer zone. Pioneer vegetation (''Spartina'') has colonized the area below the eroding cliff (see also fig. 1.A). Photographs by J. van Belzen.]]<br />
[[Image:overview of saltmarsh.JPG|thumb|none|300px| Figure 2: (A) Overview of saltmarsh by aerial photograph (RWS), comparable to situation (B.b). Cross-shoreprofile of salt‐marsh dynamics of conceptual ecomorphological model, which mimics the development of the marsh in (A). Here, (―) is the initial bare mud--‐flat profile, (―) is vegetated marsh profile at beginning, and (---) is the final profile. First, (a) saltmarsh generation due to the positive feedback between vegetation and sedimentation.Second, (b) cliff erosion of old marsh and subsequent growth at the pioneer zone (after van de Koppel, ''et al.'', 2005<ref name= "Van de Koppel"/>).]]<br />
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==VULNERABILITY & THREATS TO SALT MASRHES==<br />
===Short-term effects of flooding and storms===<br />
====SHORT-TERM FLOODING: Vulnerability of marshes to saltwater flooding====<br />
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The salt‐marsh community is well adapted to salinity due to regular tidal exposure to seawater. The vast majority of salt-marshes are well drained and therefore at less risk to the endured flooding. In comparison, the community of grazing-marshes is adapted to very dilute seawater and the habitat drainage is often slow. The potential impact of saltwater flooding is therefore more severe for [[Coastal_grazing_marsh| grazing marshes]] than for salt marshes. Much of the evidence regarding the effect of seawater on coastal vegetation therefore relates to oligohaline/grazing marshes.<br />
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====SHORT-TERM FLOODING: Effect of flooding by saline water on salt marshes ====<br />
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A flooding event that originates from increased freshwater discharge, for instance due to heavy rainfall or ice melt in a catchment area, will result in a fresh‐water pulse through downstream marshes. Unless freshwater flooding lingers for extensive periods, the impact on the vegetation of salt-and grazing- marshes will be short lived (Flynn ''et al.'', 1995<ref name= "Flynn">FLYNN, K.M.; MCKEE, .KL.; MENDELSSOHN, I.A, 1995.RECOVERY OF FRESH-WATER MARSH VEGETATION AFTER A SALTWATER INTRUSION EVENT.'' OECOLOGIA''. '''103(1)''', 63-72 DOI:10.1007/BF00328426.</ref>; Grace and Ford, 1996<ref name= "Grace">GRACE J.B., FORD M.A., 1996. The potential impact of herbivores on the susceptibility of the marsh plant ''Sagittaria lancifolia'' to saltwater intrusion in coastal wetlands. ''Estuaries''. '''19''', 13–20.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard">HOWARD R.J., MENDELSSOHN I.A., 2000. Structure and composition of oligohaline marsh plant communities exposed to salinity pulses. ''Aquat Bot''. '''68''', 143–164.</ref>). The [[Halophytic_plants|‘halophytic’]] (salt-tolerant) species that dominate salt-and grazing-marsh communities will not be harmed by short‐term fresh water exposure. However, their physiological and biochemical adaptations to cope with salinity stress make them poorly competitive under fresh water conditions (Crain ''et al., 2004''<ref name= "Crain">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549.DOI: 10.1890/03-0745 </ref>). Their halophytic traits enable them to colonise saline environments (Pennings and Callaway, 1992<ref name= "Pennings">CRAIN, C.M.; SILLIMAN B.R.; BERTNESS, S.L. ; BERTNESS, M.D., 2004. Physical and biotic drivers of plant distribution across estuarine salinity gradients. ''ECOLOGY''. '''85(9)''', 2539-2549. DOI: 10.1890/03-0745 </ref>). Salinity exposure in the salt marsh, and consequently the inherent salt tolerance of the inhabitant community, does not necessarily decline linearly with shore level. Summer evaporation of seawater pools can leave concentrated deposits of salt on the high marsh where the habitat is infrequently flushed, leading to high levels of sediment salinity that exclude less halophytic species (Watson and Burne, 2009). Paradoxically, increased frequency of seawater flushing by storms might dilute the accrued sediment salinity of such high marsh environments and alter the zonation of species. For instance, increased tidal flooding of an elevated marsh plain can cause the normally very halophytic high marsh species to be replaced by salt‐intolerant lower shore species (Watson and Burne, 2009).<br />
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The severity of impact of salt water flowing is likely to depend on the natural salinity occurring at a specific location. Relatively brackish-marshes, dominated by halophytic plants, will see less changes to community composition than fresh water dominated grazing marshes and coastal flood plains (Brown ''et al.'', 1994). Increased flooding by salt water is most likely to have the greatest effect on the fresh‐water adapted members of the marsh vegetation (Crain ''et al.'', 2004<ref name= "Crain"/>), which increases in dominance in the transitional and grazing‐marsh above the tidal marks. Stormy conditions that result in a temporary increase in sea level and which bring in salt water pulses to coastal marsh systems therefore should have a greater effect on the grazing‐marsh community than on the salt marsh community. For example, seawater flooding of a diked grazing-marsh, following a dike breaching, prevented most of the fresh water vegetation from developing in the following spring (Klein and Bateman, 1998<ref name= "Klein">KLEIN R.J.T., BATEMAN I.J., 1998. The recreational value of Cley marshes nature reserve: An argument against managed Retreat? ''Water and Environment Journal''. '''12''', 280-285. </ref>). Vegetation cover, species richness, recovery and re-establishment of an oligohaline marsh decreased during one month of experimental exposures to increased salinity (from 0.5‐5.0 salinity up to 12) (Howard and Mendelssohn, 2000<ref name= "Howard"/>). In the longer term, the space left by dead vegetation is likely to be colonised by more salinity tolerant species, and thus grazing-marsh communities might come to resemble those of salt marshes (Doody, 1982<ref name= "Doody">DOODY J.P., 1982. Sea defence and nature conservation: threat or opportunity. ''Aquat Conserv Mar Freshw Ecosyst'', '''2''', 275-283.</ref>; Howard and Mendelssohn, 2000<ref name= "Howard"/>).<br />
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Many coastal marsh plants are able to recover temporary increases in salinity (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Grace and Ford, 1996<ref name= "Grace"/>; Howard and Mendelssohn, 2000<ref name= "Howard"/>). However, the potential for lasting changes to communities increases with the duration of flooding (Flynn ''et al.'', 1995<ref name= "Flynn"/>; Howard and Mendelssohn 2000<ref name= "Howard"/>). Elevated salinity (from natural, 0.5‐5 to 15) slowed vegetation recovery more in flooded than in drained soils (Flynn ''et al.'', 1995<ref name= "Flynn"/>). The naturally slow drainage of grazing marshes, that follows temporary sea water flood, causes this habitat to remain immersed for longer periods than salt marshes. Grazing marshes are therefore at greater risk to the endured flooding. However, there are indications that these marshes are relatively resilient to exposure; if the water is brackish enough, it may require months of immersion before significant impacts to vegetation cover occurs (e.g. Howard and Mendelssohn, 2000<ref name= "Howard"/>). Brewer and Grace (1990)<ref>BREWER J.S., GRACE J.B., 1990. Plant community structure in an oligohaline tidal marsh. ''Vegetatio''. '''90''', 93–107.</ref> hypothesized that occasional storm‐generated pulses of salt water moving into an oligohaline marsh would generate short-lived salinity gradients that, along with biotic interactions, would regulate species distributions over longer terms. Sharpe and Balwin (2009)<ref name= "Sharpe">SHARPE P. J., BALWIN A.H., 2009. Patterns of Wetland Plant Species Richness Across Estuarine Gradients of Chesapeake Bay. ''Wetlands''. '''29''', 225-235.</ref> proposed that an unexpected peak in vegetation species richness in the transitional marsh arose because pulsed variation in salinity (0‐5) prevented domination by fresh water or salt water species. Thus, pulsed salinity exposure might not necessarily diminish vegetation diversity. Nevertheless, increased salt water flooding of grazing marshes is likely to drive the succession towards more salt-tolerant vegetation, and increase the resemblance with salt marsh assemblages. Note that the empirical evidence for the rate of this transition is lacking (Nicholls and Wilson, 2001<ref name= "Nicholls">NICHOLLS R.J., WILSON T., 2001. Chapter five. Integrated impacts on coastal areas and river flooding. In: Holman I.P., Loveland P.J. (Eds), Regional Climate Change Impact and Response Studies in East Anglia and North West England (RegIS). Final Report of MAFF project no. CC0337. (downloadable at [http://www.ukcip.org.uk www.ukcip.org.uk]).</ref>). The consequence of increased coastal flooding might therefore be a gradual loss of grazing-marsh communities, in exchange for gain in area cover of salt marsh communities (Doody, 1982<ref name= "Doody"/>; Klein and Bateman, 1998<ref name= "Klein"/>; Nicholls and Wilson, 2001<ref name= "Nicholls"/>). <br />
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====SHORT-TERM FLOODING: Interactions of salinity with other disturbances ====<br />
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It is important to caution against a general interpretation that seawater flooding is a minimal risk to coastal marshes in general. The severity of seawater influence on grazing‐marshes might depend much on whether the salinity is paralleled with other plant stressors and disturbances. Sharpe and Balwin (2009)<ref name= "Sharpe"/> sampled plant diversity in a marsh in the United States, across a fresh (salinity 0.5) to mesohaline (5-18) salinity gradient. In an undisturbed marsh, richness in transition zone oligohaline marshes was as high as or higher than in tidal fresh water-marshesIn an anthropogenically disturbed estuary, however, plant species richness declined linearly with an increase in salinity. Experimental flooding by brackish (6‐14) water had a greater effect on grazing‐marsh community structure and [[biomass]] when the vegetation was also disturbed by leaf clipping (Baldwin and Mendelssohn, 1998) or grazing (Gough and Grace, 1998). In comparison, flooding did not affect species richness in the absence of such additional disturbances (Baldwin and Mendelssohn, 1998). If the salinity and water regimes are permanently altered and/or the vegetation is destroyed by a combination of factors, the substrate might eventually subside. Substrate [[Natural_causes_of_coastal_erosion#Subsidence |subsidence]] and associated increased water depth might prevent seed dispersal and germination of more flooding tolerant species, and thus hamper system recovery (McKee and Mendelssohn, 1989<ref name= "Mckee en M">MCKEE K.L.; MENDELSSOHN I.A.,1989. Response of a fresh-water marsh plant community to increased salinity and increased water level. ''AQUATIC BOTANY''. '''34(4)''', 301-316. DOI: 10.1016/0304-3770(89)90074-0.</ref>).It is not known beyond which threshold the frequency of flooding will have permanent effects.<br />
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====SHORT-TERM: Vulnerability of marshes to storm damage====<br />
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As mentioned above, flooding can induce some disturbances to the vegetation composition of salt marshes. However, the threat storms impose on salt marshes is more likely to result from storm-associated damage than from flooding. Wind-induced waves can destabilize sediments, initiate and propagate lateral cliff erosion, tear of plant material, as well as deposits of wrack and debris in marshes. The [[vulnerability]] of salt marshes is largely related to the effects of waves on sediment stability and on lateral erosion. The evidence we present for the effects of storm associated erosion mostly originates from salt marshes seeing as the literature on grazing-marsh damage from salt water erosion is scarce. Severe salt marsh erosion will undoubtedly lead to an increased risk of sea water flooding and storm-associated damage for adjoined grazing‐marshes, and might eventually drive a transition of grazing‐marsh communities into salt marsh habitats.<br />
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====SHORT-TERM STORM: Sediment destabilization and lateral erosion of salt marshes====<br />
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Storm events can induce sediment stabilization and lateral erosion, which can have an important impact on the dynamics and functioning of salt marshes. Although lateral erosion is an intrinsic process for salt marshes and part of the natural cyclic behaviour, it generally gets initiated by a storm (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name= "Van de Koppel"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Such cyclic behaviour requires sufficient space for marshes to migrate landward. This space is nowadays being diminished due to anthropogenic land use. Hence, the lateral erosion of salt marshes has become a global threat, as it is unclear under which conditions an eroding marsh can re‐establish in the limited available space. For example, the marshes in the Venice Lagoon (Italy) erode 1.2-2.2 m <math>yr^{-1}</math> at their seaward edges (Day ''et al.'', 1998<ref name= "Day"/>) and estuaries of South-East England lose ~4,000 m² of tidal marsh per annum from erosion at the seaward edges and widening of creeks within the marsh (Hughes and Paramor, 2004<ref name= "Hughes"/>). In these locations, large areas of marsh are lost due to cliff erosion with little or no recovery of the vegetation. <br />
<br />
It is clear that storms contribute significantly to the loss by lateral erosion. However, the main driving factors initiating this erosion are still not clear (Wolters ''et al.'', 2005<ref name= "Wolters"/>). Human activities can be, in part, responsible for increasing erosion rates through [[pollutant]]-driven diminishing of vegetation cover and/or by enhancing hydrodynamic energy reaching the marsh via ship waves and channel dredging (Allen, 2000<ref name= "Allen"/>; Adam, 2002<ref name= "Adam"/>; Wolters ''et al.'', 2005<ref name= "Wolters"/>). Thus, there is a strong need for a fundamental understanding of the cyclic functioning of salt marsh ecosystems in order to understand when disturbances by storms will start a natural cycle of rejuvenation versus when they cause the irreversible loss of a marsh and thus would benefit from protective measures. <br />
<br />
Vulnerability of the saltmarsh to the initiation of cliff erosion will largely depend on the age of the marsh. Cliff erosion is hypothesized to be an inevitable and intrinsic consequence of the ecomorphological dynamics of saltmarshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). That is, the capture of sediment by the vegetation leads to vertical salt marsh growth, which in the long term makes the salt marsh susceptible to lateral erosion (Allen, 2000<ref name= "Allen"/>; van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). Both conceptual modelling and empirical evidence showed that a positive feedback between vegetation growth and sediment capture generates an increasingly steeper bank at the seaward edge of the marsh (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>). As a consequence, salt‐marsh edges become more vulnerable to disturbance as they mature (see Figure 1.B). This means that in the end, relatively small disturbances like from minor storm events or ship waves may induce the erosion. Data on sedimentation in salt-marshes, obtained from sediment core transects and spatiotemporal analysis of aerial photographs, support this conceptual model (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal">VAN DER WAL D., WIELEMAKER-VANDENDOOL A., HERMANP.M.J., 2008. Spatial patterns, rates and mechanisms of saltmarsh cycles (Westerschelde, The Netherlands). ''Estuarine, Coastal and Shelf Science''. '''76''', 357‐368. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=143078 www.vliz.be/imis].</ref>), suggesting that, in a wide range of circumstances, lateral retreat due to cliff erosion will happen sooner or later. <br />
<br />
[[Resilience]] of the marsh edge to erosion will depend on the interplay between vegetation composition and sediment dynamics. For instance, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=234037 Spartina]'' plants reduce cliff erosion more than ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=232101 Limonium]'' plants do due to differences in their root system. As a consequence, a ''Spartina'' dominated marsh edge is likely less vulnerable to storm events (van Eerdt, 1985). However, consequences of plant community on the vulnerability and resilience of the marsh can be more complex. The above ground plant traits can have other effects on the vegetation-sediment interaction. For example, stiffness and density of the plant may affect sedimentation rates (Bouma ''et al.'', 2005<ref name= "Bouma05"/>, 2009, 2010). The overall effect of above and below plant traits on salt‐marsh resilience/vulnerability remains largely unknown and subject to ongoing research. <br />
<br />
Alongside cliff erosion, re‐growth of pioneer vegetation on the cleared mudflat in front of the saltmarsh cliff ideally occurs, thereby rejuvenating the mature marsh (see Figure.1.B; van de Koppel, ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>). This pioneer vegetation determines the conditions for lateral retreat and gradually slows down erosion of the salt-marsh edge. <br />
<br />
The establishment of pioneer vegetation is therefore of vital importance for the development and recovery of salt marshes (van de Koppel ''et al.'', 2005<ref name="Van de Koppel"/>; van der Wal ''et al.'', 2008<ref name= "VdWal"/>; Callaghan ''et al.'', 2010<ref name= "callaghan">CALLAGHAN, D.P.; BOUMA, T.J.; KLAASSEN, P.; VAN DER WAL, D.; STIVE, M.J.F.; HERMAN, P.M.J., 2010. Hydrodynamic forcing on salt-marsh development: Distinguishing the relative importance of waves and tidal flows Est., ''Coast. and Shelf Sci.''. '''89(1)''', 73-88. dx.doi.org/10.1016/j.ecss.2010.05.013. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=206900 www.vliz.be/imis].</ref>). This emphasizes the importance of initial conditions for the establishment and growth of vegetation, and the physical conditions that may constrain these intrinsic processes for salt marsh development (van der Wal ''et al.'', 2008<ref name= "VdWal"/>). However, the factors limiting seedling establishment remain poorly understood (Bouma ''et al.'', 2009). We hypothesize that sediment destabilization plays a critical role in the ability for pioneer establishment on a mudflat and, therefore, in the ability of the salt marsh to recover from lateral cliff erosion (Balke ''et al.'', submitted; Bouma ''et al.'', submitted; van Belzen ''et al.'', in prep a; Infantes ''et al.'', submitted). <br />
</br><br />
<br />
<br />
====SHORT-TERM STORM: sediment and wrack deposits on salt marshes====<br />
<br />
Depositions of wrack, debris or large amounts of sediment, associated with extreme flooding events, can have significant effects on salt marsh vegetation. Wrack depositions may smother less hardy vegetation, leaving bare patches and opportunity for new colonization by neighbouring species, or from dispersed seeds (Bertness and Ellison, 1987<ref>BERTNESS M.D., ELLISON A.M., 1987. Determination of pattern in a New England salt marsh plant community. ''Ecol Monogr''. '''57''', 129‐14.</ref>; Tolley and Christian, 1999<ref name= "Tolley">TOLLEY P.M.; CHRISTIAN R.R., 1999. Effects of increased inundation and wrack deposition on a high salt marsh plant community. ''ESTUARIES''. '''22(4)''', 944-954.DOI: 10.2307/1353074.</ref>). Large algal mats can have residence times of 3‐4 months (Valiela and Rietsma, 1995<ref name= "Valiella">VALIELA I.; RIETSMA C.S.,1995. DISTURBANCE OF SALT-MARSH VEGETATION BY WRACK MATS IN GREAT-SIPPEWISSETT-MARSH. ''OECOLOGIA''. '''102(1)''', 106-112. </ref>). While wrack depositions may not be as significant in cover (Valiela and Rietsma, 1995<ref name= "Valiella"/>), small-scale alteration in species cover by algal wrack depositions does have the potential for wider effects on community diversity if the same spots are regularly covered by seaweed (van Hulzen ''et al.'', 2006<ref name= "van Hulzen"/>). The deposition of sediments following storm flooding may be significant. Experimental flooding and sedimentation of seedbanks of an oligohaline marsh community showed that an addition of 2 cm of sediment decreased plant density and germination of seedlings, suggesting that an increase in sedimentation and relative sea level may reduce plant biodiversity (Peterson and Baldwin, 2004<ref>PETERSON J.E., BALDWIN A.H., 2004. Seedling emergence from seed banks of tidal freshwater wetlands: response to inundation and sedimentation. ''Aquat Bot''. '''78,''' 243–254. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=59970 www.vliz.be/imis].</ref>]). The deposition of sediments might be positive for subducting and nutrient starved marshes. For example, within a year after 3-8 cm of sediment deposited by Hurricane Katrina, the vegetation of a high marsh had fully recovered and below‐ground root growth had increased 10‐fold (McKee and Cherry, 2009<ref name= "Cherry">MCKEE K.L., CHERRY J.A., 2009. Hurricane Katrina sediment slowed elevation loss in subsiding brackish marshes of the Mississippi river delta. ''Wetlands''. '''29''', 2-15.</ref>).<br />
<br />
While single factors may have limited effects on marshes, a collective of concurrent stressors is likely to generate significant impacts on marsh communities. The deposition of wrack and sediments is often concurrent with other habitat stressors that might jointly influence marsh vegetation cover. Thus, while Tolley and Christian (1999)<ref name= "Tolley"/> found little effect of sea water flooding on vegetation biomass, the simultaneous deposition of algal wrack greatly repressed plant cover and biomass, in some species irreversibly so.<br />
</br><br />
<br />
<br />
===Long-term effects due to climate change and sea level rise===<br />
<br />
[[Coastal squeeze]], due to sea level rise, and erosion are primary threats to salt marshes across Europe. They can result in reduced coastal defence value and in an increased risk of flooding. Although sea level rise may pose serious threats to the survival of salt marshes, there is growing evidence that as long as sediment supply is sufficient, the vegetation-sedimentation feedback of marshes enables marshes to accrete vertically at the rate of the rising sea-level (Kirwan and Temmerman, 2009<ref name= "KenT">KIRWAN M., TEMMERMAN S., 2009. Coastal marsh response to historical and future sea-level acceleration. ''Quaternary Science Reviews''. '''28''', 1801-1808.</ref>). However, if the suspended matter load is reduced by climate change or by significant human alteration in a catchment area, vegetation- sedimentation feedbacks can become limited, affecting the potential of marshes to accrete (Kirwan and Temmerman, 2009<ref name= "KenT"/>). As explained in the previous sections, lateral marsh erosion can become a serious threat to salt marshes over time if seedling establishment in front of the marsh is not possible so that re- growth of the marsh is prevented. Many aspects that affect the cyclic dynamics of marshes are still not well understood. Important in maintaining the vegetation-sedimentation feedback is that the sedimentary conditions remain more or less the same.<br />
<br />
Several managerial aspects are likely to compromise the capacity for marshes to persist and to protect the coast. Reduction in area by coastal squeeze will reduce the wave attenuation capacity, as the efficiency of energy reduction is strongly dependent on the depth of the marsh (Möller, 2006<ref name= "Moller">MÖLLER I., 2006. Quantifying saltmarsh vegetation and its effect on wave height dissipation: Results from a UK East coast saltmarsh. ''Estuarine Coastal and Shelf Science''. '''69''', 337‐351.</ref>). Whether this might have negative feedback on marsh accretion and accelerate area loss is not known. Effects of grazing might also reduce the vegetation‐sedimentation feedback by reducing vegetation cover and height, thereby hampering the development of salt marshes (Kiehl ''et al.'', 2007<ref name= "Kiehl07">KIEHL K., SCHRÖDER H., STOCK M., 2007. Long‐term vegetation dynamics after land‐use change in Wadden Sea salt marshes. ''Coastline Reports''. '''7''', 17‐24.</ref>). Finally, very little is known about the implications on salt marsh resilience from interactions between different environmental, climatic and managerial variables. Interactions between climate stressors (e.g. desiccation, irradiation), physical forcing (extreme flooding events, increased storminess) and environmental management (eutrophication, grazing, and managed retreat) will be a likely reality for many marshes. This is important because interactive stresses can be synergistic and cause shifts in the stable states of ecosystems, which can compromise the naturally delivered services (Scheffer ''et al.'', 2001<ref>SCHEFFER M., CARPENTER S., FOLEY J.A., FOLKER C., WALKER B., 2001. Catastrophic shifts in ecosystems. ''Nature''. '''413''': 591‐596. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=19763 www.vliz.be/imis].</ref>; Scheffer ''et al.'', 2009<ref>SCHEFFER M., BASCOMPTE J.,BROCK W. A., BROVKIN V., CARPENTER S., DAKOS V.,HELD H., VANNESE.H., RIETKERK M., SUGIHARA G., 2009. Early-warning signals for critical transitions. ''Nature''. '''461''', 53‐59. </ref>). Our evaluation of the resilience of salt marshes to disturbance, including climate change, might for the time being still be somewhat naïve and based on limited current research. <br />
</br><br />
<br />
<br />
[[Image: Chongming Dongtan.JPG|thumb|right|250px|Figure 3: Impact of sea-level rise on tidal flat and tidal marsh complex by 2050 (a and b) and 2100 (c and d) year at Chongming Dongtan nature reserve.]]<br />
====CASE STUDY: FORECASTING THE EFFECTS OF SEA‐LEVEL RISE====<br />
<br />
Located at the mouth of the Yangtze Estuary, the Chongming Dongtan nature reserve is extremely vulnerable to climate change and especially to an accelerated sea-level rise. We use a variety of data from [[remote sensing]], an in situ global positioning system (GPS), tidal gauges, nautical charts, geographic spatial analysis modelling gand IPCC sea-level rise scenarios to forecast the potential impacts of increased sea level on the coastal wetland habitat of the Chongming Dongtan Nature Reserve (Figure 3). The results indicate that around 40% of the intertidal zone of the nature reserve will be inundated by the year 2100 due to an estimated 0.88 m increase in sea level (Figure 3.c and 3.d). In particular, the ''Scirpus mariqueter'' communities and bare tidal flats are more vulnerable to sea‐level rise. The identification, mapping and statistical summary of environmental impacts of the projected sea-level rise at Chongming Dongtan Nature Reserve represent an important initial step for decision makers concerned with mitigation of the adverse impacts of sea-level rise. In this study, the inundation‐based assessment was developed to inform policymakers, managers and the public about the amount and the spatial distribution of tidal wetland change as a result of sea‐level rise. The results indicate that the zones most vulnerable to sea-level rise at the Chongming Dongtan Nature Reserve is the ''S. Mariqueter'' zone, the bare tidal flat zone and the tidal creeks, which are the most suitable habitats for migratory birds. A ~30% loss of the ''S. Mariqueter'' marsh community by the year 2100 would eliminate a rich invertebrate food source and cause deterioration in the estuarine food web for migrating birds; such a loss could arise from human-induced stressors such as land reclamation, seawall constructions, overfishing and local pollution. As tidal marshes and flats submerge and decline in size and productivity, increased crowding in the remaining areas could lead to reductions in and eventually even exclusion of some local shorebird populations (Tian ''et al.'', 2010<ref>TIAN, B; ZHANG, LQ ; WANG, XR; ZHOU, YX ; ZHANG, W.; 2010. Forecasting the effects of sea-level rise at Chongming Dongtan Nature Reserve in the Yangtze Delta, Shanghai, China. ''ECOLOGICALENGINEERING'', '''36(10)''': 1383-1388.DOI: 10.1016/j.ecoleng.2010.06.016.</ref>). <br />
</br><br />
<br />
<br />
==KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY ==<br />
===Effects of single disturbance events on marsh responses to long-term change===<br />
<br />
Single events, such as violent storms, normally have short-lived effects on the species composition and on the ecological functioning of salt-marshes (Flynn ''et al.'' 1995<ref name= "Flynn"/>, Howard and Mendelssohn, 2000<ref name= "Howard"/>; McKee and Cherry, 2009<ref name= "Cherry"/>), and are thus of less importance compared to long term persistent changes in environmental condition. Long-term processes of coastal squeeze with sea level rise and lateral erosion with increased storminess are considered to be the primary threats to salt- and grazing-marshes across Europe (Nicholls and Wilson, 2001<ref name= "Nicholls"/>. A single storm can push a marsh over the tipping point, shifting it from laterally expanding towards laterally eroding. If erosion persists, and the marsh cannot re-establish in front of the cliff, in time this will result in reduced coastal defence value and an increased risk of flooding of adjacent terrestrial environment (e.g. grazing- marshes) (Klein and Bateman, 2007).<br />
</br><br />
<br />
<br />
==CURRENT MANAGEMENT PRACTICES==<br />
===Making space for water===<br />
<br />
Currently, salt-marshes are managed extensively because of their acknowledged role in coastal protection. Many countries like e.g. the UK, the Netherlands, etc, have developed management schemes in order to make space for water along river flood plains, estuarine and coastal areas (Bakker, ''et al.'', 2005; DEFRA, 2004). This way, river run‐off and occasional high sea water levels can be attenuated by the natural buffer and retention capacity of the landscape. For example, restoring the water storage volume in an estuary can reduce the tidal prism, smoothing the tidal amplitude, which reduces the risk of flooding in up-stream estuarine areas. Salt‐marshes play an important part in this contemporary policy, because creating new marsh‐land both increases tidal water storage in up‐stream estuarine areas and wave attenuation of storm surges along exposed coast lines (Bakker ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>).<br />
</br><br />
<br />
<br />
===Managed retreat/realignment and salt-marsh engineering===<br />
<br />
The current effort to restore marsh systems in Europe and elsewhere represents graphic evidence of the political and managerial value placed on the goods and services provided by this ecosystem. The principle of ‘managed realignment’ and ‘managed retreat’ comes down to allowing salt-marsh areas, that were historically converted to alternative use for anthropogenic purposes (e.g. agricultural land or tourist development), to return to their natural state and area cover (Garbutt, ''et al.'', 2006<ref>GARBUTT, R.A.; READING, C.J.; WOLTERS, M.; GRAY, A.J.; ROTHERY, P., 2006. Monitoring the development of intertidal habitats on former agricultural land after the managed realignment of coastal defences at Tollesbury, Essex, UK. ''MARINE POLLUTION BULLETIN''. '''53(1-4)''', 155-164. DOI: 10.1016/j.marpolbul.2005.09.015.</ref>). This can be done in a number of ways, but typically involves making a breach in the historically erected barrier (seawall, dike) rather than removing the whole structure. This approach reduces the costs involved, as well as the wave action depressing the development of the vegetation. Cost benefit analyses typically show a net advantage of managed realignment over other constructed defence options (Turner, ''et al.'', 2007<ref>TURNER, R.K.; BURGESS, D .; HADLEY, D.; COOMBES, E.; JACKSON, N.; 2007. A cost-benefit appraisal of coastal managed realignment policy. ''GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS''. '''17(3-4)''': 397-407.DOI: 10.1016/j.gloenvcha.2007.05.006.</ref>). Full restoration of natural ecosystem function has met some complications. The substrates and biodiversity of pristine salt marshes is often markedly different from an artificial or restored system, even 100 years after natural processes have been allowed to operate (Hazelden and Boorman, 2001<ref>HAZELDEN J.; BOORMAN L.A.; 2001.Soils and 'managed retreat' in South East England.''SOIL USE AND MANAGEMENT''. '''17(3)''':150-154. DOI: 10.1079/SUM200166.</ref>). The implications of this managed realignment on coastal protection by marshes are not known. The MOSE project of the Venice lagoon is an impressive example of large-scale engineering to create salt‐marsh wetlands, largely for their role in dampening wave action and erosion within the lagoon (MOSE 2010).<br />
</br><br />
<br />
<br />
===Grazing management and coastal protection===<br />
<br />
There is evidence to suggest that grazing management could be of particular importance to the capacity of marshes for protecting the coast, although there has been little quantitative research on this subject (Bakker, ''et al.'', 2005). The vegetation is of key importance to coastal protection by marshes, through consolidation of the soil and by representing a structural hindrance to wash-over waves. Evidently, livestock has large potential for altering the vegetation structure directly through feeding and indirectly by altering the conditions for vegetation growth (Bakker, ''et al.'', 2005; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>). Feeding and defecation moderate vegetation structure‐composition and above- and below-ground biomass production. Trampling and hoof holes lead to soil compaction and can cause saltpan formation (Vera, 2000<ref>VERA F.W.M., 2000. Grazing Ecology and Forest History. CABI Publishing, Wallingford, UK.</ref>). The potential of management of grazing regime to influence the salt marsh coastal protection potential is therefore high. Intense grazing modifies zonation patterns and transforms complex communities with woody species into homogenous lawns dominated by short flexible grass (Andresen, ''et al.'', 1990<ref name= "Andersen">ANDRESEN H., BAKKER J.P., BRONGERS M., HEYDEMANN B., IRMLER U., 1990. Long‐term changes of salt-marsh communities by cattle grazing. ''Vegetatio''. '''89''', 137–148.</ref>; Kiehl, ''et al.'', 2007<ref name= "Kiehl07"/>), with an associated likely reduction in wave attenuation (Möller, 2006<ref name= "Moller"/>) and sedimentation rates (Andresen, ''et al.'', 1990<ref name= "Andersen"/>). Grazing at low intensity increases vegetation patchiness and biodiversity due to selective grazing of palatable species (Bakker, 1985<ref>BAKKER J. P., DIJKSTRA M., RUSSCHEN P. T., 1985. Dispersa, germination and early establishment of halophytes and glycophytes on a grazed and abandoned salt‐marsh gradient. ''New Phytologist''. '''101''', 291-308.</ref>, 1998; Kiehl ''et al.'', 1996<ref>KIEHL K., EISCHEID I., GETTNER S., WALTER J., 1996. Impact of different sheep grazing intensities on salt-marsh vegetation in northern Germany. ''Journal of Vegetation Science''. '''7''', 99–106.</ref>; Adler ''et al.'', 2001<ref>ADLER P.B.; RAFF D.A.; LAUENROTH W.K.;, 2001.The effect of grazing on the spatial heterogeneity of vegetation. ''OECOLOGIA''. '''128(4)''': 465-479.</ref>; Bouchard ''et al.'', 2003<ref>BOUCHARD V.; TESSIER M.; DIGAIRE F.; VIVIER, J.P.; VALERY, L.; GLOAGUEN, J.C.; LEFEUVRE, J.C., 2003. Sheep grazing as management tool in Western European saltmarshes.InternationalCongress on Biodiversity Conservation and Management. ''COMPTES RENDUS BIOLOGIES''. '''326''', S148-S157.DOI: 10.1016/S1631-0691(03)00052-0.</ref>; Marriot ''et al.'' 2005). Patchiness may cause specific spatial patterns in turbulence and sedimentation (Boorman, 1999; van Wesenbeeck, ''et al.'', 2007), so that the sum effect of patchiness on marsh coastal protection is not known. Conversely, grazing pressure can lead to greater resource allocation of below‐ground biomass (Pucheta, ''et al.'', 2004<ref>PUCHETA, E.; BONAMICI, I.; CABIDO, M.; DIAZ, S.; 2004. Below-ground biomass and productivity of a grazed site and a neighbouring ungrazed exclosure in a grassland in central Argentina. ''AUSTRALECOLOGY''. '''29(2)''', 201-208.DOI: 10.1111/j.1442-9993.2004.01337.x. </ref>), thus reducing surface erosion and below-ground contributions to an increase in marsh surface elevation. <br />
</br><br />
<br />
<br />
==see also==<br />
<br />
[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
<br />
[[Salt_marshes |Salt marshes]]<br />
<br />
[[Natural_barriers#Salt_marshes | Natural barriers, salt marshes]]<br />
<br />
[[Salt_marches_in_Europe_and_temporal_variability |Salt marches in Europe and temporal variability]]<br />
</br><br />
</br><br />
<br />
==References==<br />
<references/></br><br />
<br />
[[Category: Salt marshes ]]<br />
[[Category: Coastal erosion ]]<br />
[[Category: Biodiversity and habitat loss]]<br />
<br />
{{ 5Authors<br />
|AuthorID1=25081<br />
|AuthorFullName1= van Belzen, Jim<br />
|AuthorID2=8361<br />
|AuthorFullName2= Bouma, Tjeerd<br />
|AuthorID3=20719<br />
|AuthorFullName3= Skov, Martin<br />
|AuthorID4=20751<br />
|AuthorFullName4= Zhang, Liquan<br />
|AuthorID5=?<br />
|AuthorFullName5= Yuan, Lin<br />
}}</div>Katreineblommehttps://www.coastalwiki.org/w/index.php?title=Dynamics,_threats_and_management_of_biogenic_reefs&diff=50190Dynamics, threats and management of biogenic reefs2012-07-24T12:47:03Z<p>Katreineblomme: </p>
<hr />
<div>__TOC__<br />
<br />
==PROCESSES AND MECHANISMS DRIVING NATURAL DYNAMICS & ECOSYSTEM DEVELOPMENT ==<br />
Biogenic [[reef]]s can be described as hard compact structures created by the activity of living organisms <ref name= "Biogenic reef">[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]</ref>. They do not share an uniform structure<ref name= "Biogenic reef"/> and vary in spatial scale. Moreover, the life they support is greatly dependent upon location and composition<ref>[[Natural_barriers#Biogenic_reefs |Natural barriers]]</ref>. Dense colonies of several species are widely considered to be reef in Europe. Only four of these species are described in this report due to their contribution to sediment entrainment, bed stability and potential wave energy attenuation, these are: ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130867 Sabellaria spinulosa]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=130866 Sabellaria alveolata]'', ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138228 Mytilius spp.]'' and ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140467 Modiolus modiolus]''<ref name= "Biogenic reef"/>. In this section, the processes and mechanisms driving natural dynamics and ecosystem development of biogenic reefs are discussed for each group in turn.<br />
<br />
</br> <br />
==='''''Sabellaria spinulosa'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
<br />
<br />
''S. spinulosa'' (or Ross worm) is thought to require stable foundations on which to settle and establish a tube (Jackson, 1977<ref>JACKSON J., 1977. Competition on marine hard substrata: the adaptive significance of solitary and colonial strategies. ''The American Naturalist''. '''111''', 743-767. </ref>; Wood, 1999<ref>WOOD R., 1999. Reef Evolution. Oxford University Press, Oxford. pp. 414. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=60081 www.vliz.be/imis]</ref>; Chisholm and Kelley, 2001<ref>CHISHOLM J.R.M., & KELLEY R., 2001. Worms start the reef-building process. ''Nature''. '''409''', 152 153.</ref>) and is thus likely to favour substrata which include bedrock; boulders, cobbles, mixed substrata; and mixed [[sediment]] (Connor ''et al.'', 1997<ref name= "Conner97">CONNOR D., DALKIN M., HILL T., HOLT R. & SANDERSON W., 1997. Marine Nature Conservation Review: marine biotope classification for Britain and Ireland. Volume 2. Sublittoral biotopes. Version 97.06. Joint Nature Conservation Committee, Peterborough. pp 448. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=21440 www.vliz.be/imis].</ref>). Although it is assumed that a firm substratum is required for colony establishment, it has been suggested that a reef can increase in extent without the need for hard substratum (Holt ''et al.'', 1997<ref>HOLT T., HARTNOLL R. & HAWKINS S., 1997. Sensitivity and vulnerability to man‐induced change of selected communities: intertidal brown algal shrubs, ''Zostera'' beds and ''Sabellaria spinulosa'' reefs. ''English Nature Research Reports''. No. 234. pp97.</ref>). Many studies have reported extensive colonies in predominantly sandy areas (Warren and Sheldon, 1967<ref>WARREN P.J., SHELDON R.W., 1967. Feeding and migration patterns of the Pink Shrimp ''Pandalus montagui'', in the estuary of the River Crouch, England, ''Journal of the Fisheries Research Board of Canada''. '''24''', 569-580.</ref>; Schäfer, 1972<ref name= "Schafer">SCHAFER W., 1972. Ecology and Palaeoecology of Marine Environments. Translation of Aktuo-paläontologie nach Studien in der Nordsee. University of Chicago Press, Chicago. pp 568. Availbale from: [http://www.vliz.be/imis/imis.php?module=ref&refid=11646 www.vliz.be/imis].</ref>; Warren, 1973<ref>WARREN P., 1973. The fishery for the pink shrimp Pandalus montagui of the Wash. Laboratory Leaflet (New Series) No. 28. Ministry of Agriculture, Fisheries and Food, Lowestoft. pp. 46.</ref>; Limpenny ''et al.'', 2010<ref>LIMPENNY D.S., FOSTER‐SMITH R.L., EDWARDS T.M., HENDRICK V.J., DIESING M., EGGLETON J.D., MEADOWS W.J., CRUTCHFIELD Z., PFEIFER S., & REACH I.S., 2010.Best methods for identifying and evaluating ''Sabellaria spinulosa'' and cobble reef. Aggregate Levy Sustainability Fund Project MAL0008. Joint Nature Conservation Committee, Peterborough. pp 134.</ref>). Recent observations from The Wash, England show that ''S. spinulosa'' had ‘seeded’ on shell fragments predominantly from blue or horse mussels (Ian Reach, Natural England, pers. comm.). <br />
<br />
As ''S. spinulosa'' is a sedentary [[species]], it relies on wave and current action to supply food and wash away waste products (Kirtley, 1992<ref name= "Kirtley">KIRTLEY D.J., 1992. Built to last. Worm reefs. A feat of natural engineering. ''Florida Oceanographic Magazine''. '''13''', 12‐19.</ref>). Strong water movement is required for food provisions, but is perhaps more important to raise sediment into suspension for tube building (Jones, 1999<ref>JONES L., 1999. Habitat Action Plan: ''Sabellaria spinulosa'' reefs. English Nature. pp 4.</ref>). As a result, ''S. spinulosa'' colonies are typically located in areas of weak to moderately strong water flow (Jones ''et al.'', 2000<ref>JONES L.A., HISCOCK K., CONNOR D.W., 2000. Marine habitat reviews. A summary of ecological requirements and sensitivity characteristics for the conservation and management of marine SACs. Joint Nature Conservation Committee, Peterborough. (UK Marine SACs Project report).</ref>). It also appears to favour locations around the edges of sand banks or areas with sand waves (Foster‐Smith, 2001<ref name= "Foster-Smith">FOSTER‐SMITH R.L., 2001. Report of the field survey for the 2001 ''Sabellaria spinulosa'' project. A report for the Eastern Sea Fisheries Joint Committee and English Nature. pp 45.</ref>). ''S. spinulosa'' typically occurs [[subtidal]]ly in depths of a few meters to up to 40 m depth (Caspers, 1950<ref>CASPERS H., 1950. Die Lebensgemeinschaft der Helgolander Austernbank. ''Helgoland Marine Research''. '''3''', 119-169. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=70537 www.vliz.be/imis].</ref>; George and Warwick<ref name= "George">GEORGE C., & WARWICK R., 1985. Annual production in a hard‐bottom reef community. ''Journal of the Marine Biological Association of the United Kingdom''. '''65''', 713-735. Availble from: [http://www.vliz.be/imis/imis.php?module=ref&refid=15832 www.vliz.be/imis].</ref>, 1985; Connor ''et al''., 1997<ref name= "Conner97"/>; Jessop and Stoutt, 2006<ref name= "Jessop">JESSOP R. & STOUTT J., 2006. Broad scale ''Sabellaria spinulosa'' distribution in the central Wash (Southern North Sea), as predicted with the acoustic ground discriminating system (A.G.D.S) RoxannTM. Draft report by the Eastern Sea Fisheries Joint Committee for English Nature. pp 26.</ref>), but can occur in depths up to 600 m (Hartmann-Schröder, 1971). S. spinulosa occasionally occurs in the lower [[intertidal]] zone (Jessop and Stoutt, 2006<ref name= "Jessop"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The fecundity and recruitment of ''S. spinulosa'' is known to be variable (e.g. Linke, 1951<ref name= "Linke">LINKE O., 1951. Neue Beobachtungen uber Sandkorallen‐Riffe in der Nordsee, ''Natur u.Volk.''. '''81''', 77-84.</ref>; Wilson, 1971<ref name= "Wilson71">WILSON D.P., 1971. ''Sabellaria'' colonies At Duckpool, North Cornwall, 1961‐1970. Journal of the Marine Biological Association of the UK, 51: 509‐580. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=108453 www.vliz.be/imis].</ref>; Michaelis, 1978<ref>MICHAELIS H., 1978. Recent biological phenomena in the German Waddensea. Symposium on North Sea fish stocks-recent changes and their causes., Aarhus (Denmark).</ref>; George and Warwick, 1985<ref name= "George"/>). The family Sabellariidae are broadcast spawners, reproducing sexually, resulting in larvae that drift passively in the [[plankton]] (Schäfer, 1972<ref name= "Schafer"/>; Eckelbarger, 1978<ref name= "Eckelbarger">ECKELBARGER K.J., 1978. Metamorphosis and settlement in the Sabellariidae. In: Chai, F.-S. & Rice, M. (Eds.). Settlement and Metamorphosis of Marine Invertebrate Larvae.Proceedings of the Symposium on Settlement and Metamorphosis of Marine Invertebrate Larvae, American Zoological Society Meeting. Totonto, Ontario, Canada December 27-28, 1977. Elsevier, New York: pp. 145-164.</ref>). The larvae can spend a few weeks to several months in the plankton (Wilson, 1929<ref name= "WIlson29">WILSON D.P., 1929. The larvae of the British Sabellarians. ''Journal of the Marine Biological Association of the United Kingdom''. '''15''', 221‐269. </ref>) before seeking appropriate conditions for settlement (Wilson, 1968<ref name= "Wilson68">WILSON D.P., 1968.The settlement behavior of the larvae of ''Sabellaria alveolata''. ''Journal of the Marine Biological Association of the United Kingdom''. '''48''', 387‐435.</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>). If conditions are unsuitable, the larvae are able to delay metamorphosis for several weeks. Physical factors alone have limited influence on settlement (Wilson, 1968<ref name= "Wilson68"/>) and settlement and metamorphosis is strongly influenced by the tube cement of other sabellariids (Wilson, 1968<ref name= "Wilson68"/>; 1970<ref name= "Wilson70">WILSON D.P., 1970. The larvae of ''Sabellaria Spinulosa'' and their settlement behaviour. ''Journal of the Marine Biological Association of the United Kingdom''. '''50''', 33-52. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=108457 www.vliz.be/imis].</ref>; Eckelbarger, 1978<ref name= "Eckelbarger"/>; Jensen, 1992<ref>JENSEN R.A., 1992. Marine bioadhesive: role for chemosensory recognition in a marine invertebrate. Biofouling. '''5''', 177-193.</ref>). This mechanism ensures settlement in a suitable [[habitat]] and promotes the development of large colonies.<br />
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Despite only a few studies investigating the rate at which ''S. spinulosa'' can extend their dwelling tubes (Hendrick, 2007<ref name= " Hendrick ">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref>; Davies ''et al.'', 2009<ref>DAVIES A.J., LAST K.S., ATTARD K., HENDRICK V.J., 2009. Maintaining turbidity and current flow in laboratory aquarium studies, a case study using ''Sabellaria spinulosa''. ''Journal of Experimental Marine Biology and Ecology''. '''370''', 35-40.</ref> being exceptions), it appears that sabellariid reefs develop quickly following successful settlement (Linke, 1951<ref name= "Linke"/>; Vorberg, 2000<ref name= " Vorberg ">VORBERG R., 2000. Effects of the shrimp fisheries on reefs of ''Sabellaria spinulosa'' (Polychaeta). ''ICES Journal of Marine Science''. '''57''', 1416-1420.</ref>; Stewart ''et al.'', 2004<ref>STEWART R.J., WEAVER J.C., MORSE D.E. & WAITE J.H., 2004. The tube cement of ''Phragmatopoma californica'': a solid foam. ''Journal of Experimental Biology''. '''207''', 4727-4734.</ref>; Braithwaite ''et al.'', 2006<ref>BRAITHWAITE C.J.R., ROBINSON R.J., & JONES G., 2006. Sabellarids: a hidden danger or an aid to subsea pipelines? ''Quarterly Journal of Engineering Geology and Hydrogeology''. '''39''', 259‐265.</ref>). Last ''et al.'' (2011)<ref>LAST K.S., HENDRICK V.J., BEVERIDGE C.M. & DAVIES A.J., 2011. Measuring the effects of suspended particulate matter and smothering on the behaviour, growth and survival of key species found in areas associated with aggregate dredging. Report for the Marine Aggregate Levy Sustainability Fund, Project MEPF 08/P76. 69 pp.</ref> observed that tube extension rates are highly variable and that they could grow up to 6 mm a day for several days when provided with an adequate sediment supply. <br />
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Little is known about the longevity of ''S. spinulosa'' colonies, but sabellariids are expected to survive for 1-2 years (Kirtley, 1966<ref>KIRTLEY D.J., 1966. Intertidal reefs of Sabellariidae (Annelida polychaeta) along the coasts of Florida. Masters thesis. The Florida State University. Tallahassee, Florida. 104 pp. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007). ''Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. Marine Biology''. '''150(3)''', 345‐358. </ref>; McCarthy, 2001<ref>MCCARTHY D., 2001. Life-history patterns and the role of disturbance in intertidal and subtidal populations of the polychaete ''Phragmatopoma lapidosa lapidosa'' (Kinberg, 1867) in the tropical Western Atlantic. PhD Thesis. Kings College, University of London. Original reference not seen. Cited by Drake, C.A., McCarthy, D.A. & von Dohlen, C.D. (2007).Molecular relationships and species divergence among ''Phragmatopoma'' spp. (Polychaeta: Sabellaridae) in the Americas. ''Marine Biology''. '''150(3)''', 345‐ 358.</ref>; McCarthy ''et al.'', 2003<ref>MCCARTHY D., YOUNG C. & EMSON R., 2003. Influence of wave induced disturbance on seasonal spawning patterns in the sabellariid polychaete ''Phragmatopoma lapidosa''. ''Marine Ecological Progress Series''. '''256''', 123-133.</ref>), with some reports of longer life spans (Wilson, 1974<ref name= "Wilson74">WILSON D.P., 1974. Sabellaria Colonies at Duckpool, North Cornwall, 1971–1972, With a Note for May 1973. ''Journal of the Marine Biological Association of the United Kingdom''. '''54''', 393‐436.</ref>; George and Warwick, 1985<ref name= "George"/>). It is likely that the age of an actual colony may greatly exceed the age of the oldest individuals. This is particularly likely as sabellariid larvae are stimulated to metamorphose by conspecific secretions, encouraging continuous succession of generations.<br />
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[[image:Sabellaria alveolata.jpg|center|thumb|400px|caption|FFigure 1: Images illustrating the various stages of development of ''S.alveolata'' reef at Bude, Cornwall (photos L. Firth). ]]<br />
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==='''''Sabellaria alveolata'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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''S. alveolata'' (or honeycomb worm) generally requires hard substrata on which to develop, but these must be in areas with a good supply of suspended coarse sediment for tube building. ''S. alveolata'' reefs are known to form on a range of substrata from pebble to bedrock (Cunningham ''et al.'', 1984<ref name= "Cunningham">CUNNINGHAM P.N., HAWKINS S.J., JONES H.D., BURROWS M.T., 1984. The geographical distribution of Sabellaria alveolata (L.). '''In:''' England, Wales and Scotland, with investigations into the community structure of, and the effects of trampling on Sabellaria alveolata colonies. Report to the Nature Conservancy Council from the Department of Zoology, Manchester University, Manchester. NCC report No. HF3/11/22.</ref>). Reefs therefore commonly form on bodies of rock or boulders surrounded by sand. Larsonneur (1994)<ref>LARSONNEUR C. 1994. The Bay of Mont‐Saint‐Michel: A sedimentation model in a temperate macrotidal environment. ''Senckenbergiana maritima''. '''24''', 3‐63.</ref> noted that settlement of ''S. alveolata'' was facilitated by the sand mason ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=131495 Lanice conchilega]'' which can stabilize sand well enough to allow colonization by ''S. alveolata''. Settlement occurs mainly on existing colonies or their dead remains (Figure 1). <br />
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Water movement of sufficient intensity is a prime requirement to suspend coarse sand particles, thus making them available for the building of worm tubes. Cunningham ''et al.'' (1984)<ref name= "Cunningham"/> note that this may consist of waves or currents. In many British localities such as the south west of England, much of Wales and the Cumbrian coast, the former seem more important. In other areas, such as parts of the Severn Estuary, tidal suspension is probably very important. However, ''S. alveolata'' is generally absent in very exposed peninsulas such as the Lleyn, Pembrokeshire and the extreme south west of Cornwall, which probably relates to the effect of water movement on recruitment (Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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It is thought that the larvae of ''S. alveolata'' spend 6 weeks to 6 months in the plankton (Wilson, 1968<ref name= "Wilson68"/>; Wilson, 1971<ref name= "Wilson71"/>) in order to attain widespread dispersal. The most detailed work done on ''S. alveolata'' reproduction in the British Isles is that of Wilson in Cornwall (e.g. Wilson, 1971<ref name= "Wilson71"/>). Wilson observed slight settlement in every month except July, but in 14 years of monitoring (1961 to 1975), Wilson (1976)<ref name= "Wilson76">WILSON D.P., 1976. ''Sabellaria Alveolata'' (L.) At Duckpool, North Cornwall, 1975. ''Journal of the Marine Biological Association of the United Kingdom''. '''56''', 305-310.</ref> observed only three heavy settlements: in 1966, 1970 and 1975. All occurred from September to November or December. Subsequent studies have revealed that the intensity of settlement is extremely variable, both temporally and spatially (Gruet, 1982<ref name= "Gruet">GRUET Y., 1982. Recherches sur l’écologie des récifs d’Hermelles édicés par l’Annélide Polychète ''Sabellaria alveolata'' (Linné), Université des Sciences et Techniques, Nantes, France. PhD.</ref>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). Settlement occurs mainly on existing colonies or their dead remains; chemical stimulation seems to be involved, and this can come from ''S. spinulosa'' tubes as well as from ''S. alveolata'' (Wilson, 1971<ref name= "Wilson71"/>; Gruet, 1982<ref name= "Gruet"/>; Cunningham ''et al.'', 1984<ref name= "Cunningham"/>). <br />
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==='''''Mytilus spp.'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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The widespread distribution of the ''M. edulis'' is a reflection of its tolerance of a wide range of environmental variables. Natural reefs typically occur on firm, mixed sediments in relatively wave sheltered estuaries and bays characterized by strong currents (Holt ''et al.'', 1998<ref name= "Holt98">HOLT T.J., REES E.I., HAWKINS, S.J., SEED, R., 1998. Biogenic Reefs (volume IX). An overview of dynamic and sensitivity characteristics for conservation management of marine SACs. Scottish Association for Marine Science (UK Marine SACs Project). 170 pp.</ref>). In more exposed areas, larger colonies are only able to develop on hard and stable substrata such as rock or large boulders (Seed, 1969<ref name= "Seed">SEED R., 1969. The ecology of ''Mytilus edulis'' L. (Lamellibranchiata) on exposed rocky shores. ''Oecologia''. '''3''', 317‐350.</ref>). Conversely, in sheltered environments large beds may develop on more sandy substrates (Roberts and McKenzie, 1983<ref>ROBERTS D., & MCKENZIE J.D., 1983. Utilisation of mollusk resources in N. Ireland. ''Journal of Molluscan Studies''. '''49''', 162-166.</ref>).<br />
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Mussels produce byssal threads which anchor them to the substratum and each other, enabling large beds to develop. Mussels can grow in all but the most exposed conditions where their byssus threads can provide anchorage against wave action and water flow. As ''M. edulis'' is a sessile filter feeder, it requires sufficient water to flow to bring food and wash away waste. Larger beds require higher flow in order to provide sufficient food supply to high numbers of individuals. It is generally considered that this water movement is best provided by tidal currents rather than wave action, though the latter may also contribute in some areas (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
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''M. edulis'' is tolerant of a wide range of salinities, being found in locations ranging from estuarine to fully marine, but larger reefs typically occur within the lower third of the intertidal and in the mid to lower reaches of the estuary (Holt ''et al.'', 1998<ref name= " Holt98 "/>). ''M. edulis'' reefs do form subtidally and have been reported to occur at depths of 30 m (Ian Reach, Natural England, pers. comm.). The upper limits of M. edulis are thought to be set by temperature and desiccations stress (Seed and Suchanek, 1992<ref name= "Suchanek">SEED R. & SUCHANEK T.H., 1992. Population and community ecology of ''Mytilus''. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. ''Developments in Aquaculture and Fisheries Science''. '''25''', Elsevier, Amsterdam: pp. 87-170. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9203 www.vliz.be/imis].</ref>) in addition to reduced feeding (Widdows and Shick, 1985<ref>WIDDOWS J., & SHICK J.M., 1985. Physiological responses of ''Mytilus edulis'' and ''Cardium edule'' to aerial exposure. ''Marine Biology''. '''85''', 217-232. </ref>). The lower limits are generally set by biological factors such as competition and predation with physical factors playing a secondary role (Holt ''et al.'', 1998<ref name= " Holt98 "/>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
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The ''M. edulis'' fecundity and recruitment success is highly variable, both temporally and spatially. It can reproduce in its first year and can spawn throughout the year, with a major spawning event usually occurring in the spring (Seed, 1969<ref name= " Seed "/>). Larvae can survive in the plankton for 2‐4 weeks before metamorphosis, although this can be up to 6 months, depending on availability of food, suitable substrate and temperature (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Settlement can be either a one-stage or a two‐stage process. Some larvae can settle directly onto adult beds (McGrath ''et al.'', 1988<ref name= "Mcgrath">MCGRATH D., KING P., & GOSLING E., 1988. Evidence for the direct settlement of ''Mytilus edulis'' larvae on adult mussel beds. ''Marine Ecological Progress Series''. '''47''', 103‐106.</ref>) or they can temporarily settle onto sublittoral filamentous substrata such as [[algae]] or hydroids before becoming detached, and eventually settling onto an adult bed (Bayne, 1964; Pulfrich, 1996<ref>Pulfrich, A., 1996; Attachment and settlement of post-larval mussels (''Mytilus edulis L'') in the Schleswig-Holstein Wadden Sea Source. ''JOURNAL OF SEA RESEARCH''. '''36(3-4)''', 239-250. DOI: 10.1016/S1385-1101(96)90793-5.</ref>). It is thought that this may be a mechanism for reducing competition between very young and adult mussels, and/or to prevent filtration of the larvae by the adult mussels. McGrath ''et al.'' (1988)<ref name= "Mcgrath"/> reported very large densities of settling spat in Ireland, but more commonly modest recruitment between the shells of adult mussels provides sufficient supply to maintain persistent beds (Holt ''et al.'', 1998<ref name= " Holt98 "/>). Conversely, heavy recruitment may not necessarily lead to the formation or maintenance of a dense bed or reef if predation or losses due to wave action are high. <br />
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''M.edulis'' growth and production can be extremely high, particularly in sheltered or estuarine areas (Holt ''et al.'', 1998). It has been reported that ''M. edulis'' accounts for 20% of the total macrobenthic production in the Wadden Sea (Beukema , 1981<ref>Beukema, J.J. (1981). Quantitative data on the benthos of the Wadden Sea proper. '''In''': Dankers, N.M.J.A. ''et al''. (1981).Invertebrates of the Wadden Sea: final report of the section 'Marine Zoology' of the Wadden Sea Working Group. Wadden Sea Working Group Report, 4: pp. 134-142. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=34980 www.vliz.be/imis].</ref>), whilst Dare (1976)<ref name= "Dare">DARE P.J., 1976. Settlement, growth and production of the mussel, ''Mytilus edulis'' L., in Morecambe Bay, England. Fishery Investigations, Ministry of Agriculture, Fisheries and Food. Pp 25. Original reference not seen. Cited by Tyler‐Walters, H. (2008). ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''.</ref> estimated the production by two year classes to be 2.5‐3 times their maximum standing crop, with few mussels surviving beyond their third year. It is thought that the majority of mussels do not survive beyond 3 years of age (Seed, 1976<ref name= "Seed76">SEED R., 1976. Ecology. '''In''': Bayne, B. (Ed.). Marine mussels: their ecology and physiology. International Biological Programme 10. Cambridge University Press, Cambridge: pp. 13‐66. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=215589 www.vliz.be/imis].</ref>), there are reports of individuals surviving beyond 15 years (Sukhotin ''et al.'', 2007<ref>SUKHOTIN A.A., STRELKOV P.P., MAXIMOVICH N.V. & HUMMEL H., 2007. Growth and longevity of ''Mytilus edulis'' (L.) from northeast Europe. ''Marine Biology Research''. '''3''', 155-167. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=111766 www.vliz.be/imis].</ref>).<br />
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==='''''Modiolus modiolus'''''===<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Environmental Requirements'''</span><br />
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Despite typically occurring on hard substrata, ''M. modiolus'' (or horse mussel) beds and reefs are capable of forming on a variety of sedimentary bottoms, ranging from muddy substrata in some sea lochs to quite coarse mixed sediments containing much stones and shell. Larvae can also settle on artificial substrates such as oil rigs and can form reefs on these structures. The byssus threads of adult ''M. modiolus'' provide a suitable substrate for attachment and protection from predators. Beds occurring infaunally can lack available byssus threads and thus limit the recruitment (Holt and Shalla, 1997<ref name= " Holt97 ">HOLT T.J., & SHALLA S.H.A., 1997. Pre- and post-drilling survey of block IOM 112/19, A report to Elf Enterprise Caledonia Ltd. By Port Erin Marine Laboratory, University of Liverpool. Unpublished work.</ref>) and the development of larger beds. <br />
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''M. modiolus'' has a very wide depth distribution, typically being found subtidally from a few meters of depth right down to depths of 280 m (Schweinitz and Lutz, 1976<ref>SCHWEINITZ E., & LUTZ R., 1976. Larval development of the northern horse mussel, ''Modiolus modiolus'' (L.), including a comparison with the larvae of ''Mytilus edulis'' L. as an aid in planktonic identification. ''Biological Bulletin''. '''150''', 348‐360.</ref>). Intertidal populations have occasionally been reported (Davenport and Kjosvik, 1982<ref name= " Davenport">DAVENPORT J. & KJORSVIK E., 1982. Observations on a Norwegian intertidal population of the horse mussel ''Modiolus modiolus'' (L.). ''Journal of Molluscan Studies''. '''48''', 370‐371.</ref>), but these are thought to be limited by temperature and desiccation stress associated with aerial exposure (Coleman, 1976<ref>COLEMAN N.,1976. Aerial respiration of ''Modiolus modiolus''. ''Comparative Biochemistry and Physiology Part A: Physiology''. '''54''', 401‐406. </ref>; Davenport and Kjosvik, 1982<ref name= " Davenport"/>). The densest populations that are known as reef are found between 5 and 50 m in British waters (Holt ''et al.'', 1998<ref name= "Holt98"/>), whilst infaunal reefs have been found at over 80 m in the Bay of Fundy (Wildish ''et al.'', 2009<ref>WILDISH D.J., FADER G. & PARROTT D., 2009. A model of horse mussel reef formation in the Bay of Fundy based on population growth and geological processes. ''Atlantic Geology''. '''45''', 157-170.</ref>).<br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Reproduction and Development'''</span><br />
<br />
''M. modiolus'' is a long-lived species with individuals only reaching sexual maturity between 3 and 6 years of age. It is thought that this adaptation is in response to high predation on juvenile mussels, thereby channeling energetic resources towards growth in early life. As a result, ''M. modiolus'' exhibits rapid growth in the first few years of life, followed by much slower growth following sexual maturation (Anwar ''et al.'', 1990<ref name= " Anwar ">ANWAR N. A., RICHARDSON C.A., & SEED R., 1990. Age determination, growth rate and population structure of the horse mussel Modiolus modiolus. ''Journal of the Marine Biological Association of the United Kingdom''. '''70''', 441-457.</ref>). ''M. modiolus'' spawning is known to be variable, both temporally and spatially. In Strangford Lough, Northern Ireland, slight spawning is known to occur year-round, with no apparent peak (Seed and Brown, 1977<ref name= "Seed77">SEED R., & BROWN R.A., 1977. Comparison of reproductive cycles of ''Modiolus modiolu'' (L), ''Cerastoderma (= Cardium) edule'' (L), and ''Mytilus edulis L'' in Strangford Lough, Northern Ireland. ''Oecologia''. '''30''', 173-188. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=195549 www.vliz.be/imis].</ref>; Brown, 1984<ref name= " Brown84 ">BROWN R.A. 1984. Geographical variations in the reproduction of the horse mussel, ''Modiolus modiolus'' (Mollusca: bivalvia). ''Journal of the Marine Biological Association of the United Kingdom''. '''64''', 751-770.</ref>). Conversely, in Scandinavia, a spawning peak occurs in June, followed by a period of gonad redevelopment. Spawning is temperature dependent and is reported to occur within a narrow temperature range (7-10 °C). It is thought that the relatively constant temperatures in Strangford Lough facilitate the year-round spawning (Brown, 1984<ref name= " Brown84 "/>). M. modiolus in the Irish Sea off the SE coast of the Isle of Man has been observed to follow an annual cycle of gonad development with a peak occurring in spring/summer, with trickle spawning occurring all year round (Jasim and Brand, 1989<ref>JASIM A.K., & BRAND A.R., 1989. Observations on the reproduction of ''Modiolus modiolus'' in Isle of Man waters. ''Journal of the Marine Biological Association of the UK''. '''69''', 373-385.</ref>). <br />
<br />
</br><br />
==VULNERABILITY & THREATS==<br />
=== GENERAL SUMMARY ===<br />
<br />
This section is divided up into (1) the vulnerability and (2) the threats (biological, chemical and physical) to each species in turn: ''Sabellaria spinulosa''; ''Sabellaria alveolata''; ''Mytilus'' spp. and ''Modiolus modiolus''. <br />
<br />
In this section, we refer to the [[sensitivity]], [[vulnerability]] and potential for recovery of the habitat to sea level rise and storm events. In the case of natural reefs, flooding is not applicable and is therefore not discussed here. Much of the information from this section was sourced from the Marine Life Information Network website ([http://www.marlin.ac.uk]). We have adopted the terminology used by MarLIN with definitions below. In the following sections, we have identified the factors that are most likely to be associated with sea level rise and storm events for each species. The ‘intolerance’, ‘sensitivity’ and ‘recoverability’ of each species are presented in table format. <br />
<br />
'''Intolerance''' is the susceptibility of a habitat, community or species (i.e. the components of a biotope) to damage, or death, from an external factor. Intolerance must be assessed relative to change in a specific factor.<br />
<br />
'''Recoverability''' is the ability of a habitat, community, or species (i.e. the components of a biotope) to return to a state close to that which existed before the activity or event caused change. <br />
<br />
'''Sensitivity''' is dependent on the intolerance of a species or habitat to damage from an external factor and the time taken for its subsequent recovery. For example, a very sensitive species or habitat is one that is very adversely affected by an external factor arising from human activities or natural events (killed/destroyed, 'high' intolerance) and is expected to recover over a very long period of time, i.e. >10 or up to 25 years ('low'; recoverability). Intolerance and hence sensitivity must be assessed relative to change in a specific factor. <br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<br />
''S. spinulosa'' is generally considered to be a very tolerant species with limited sensitivity (Table 1). Perhaps, the greatest sensitivity is to substratum loss, as once dislodged, the individual worms cannot rebuild their tubes. ''S. spinulosa'' is often one of the first species to recolonise an area after a disturbance (Cooper ''et al.'', 2007). Therefore, this species is expected to have a high recoverability. <br />
<br />
''S.spinulosa'' is most frequently found in polluted and disturbed conditions. ''S. spinulosa'' occurs in high densities on subtidal gravels that would be expected to be disturbed every year or perhaps once every few years due to storms and in polluted conditions. ''S. spinulosa'' appears to be very tolerant of water quality variation, but is potentially vulnerable to the short‐term and localized effects of mineral extraction and the effects of oil dispersants on the larvae. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%";>'''Table 1: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''S. spinulosa''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
| Low<br />
| High<br />
| Low<br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
| Immediate<br />
| Not sensitive<br />
| Moderate<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|High<br />
|High<br />
|Moderate<br />
|Low<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Sabellaria alveolata '''''====<br />
<br />
Similar to ''S. spinulosa'', recolonisation of individual ''S. alveolata'' is expected to be high, as long as there is suitable substratum for the settlement of larvae (Table 2). Recovery of reefs is expected to take considerably longer. <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 2: List of levels of “intolerance”, “recoverability”’ and “sensitivity” for physical and chemical threats to ''S. alveolata''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources). '''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
| High<br />
| Low<br />
|low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Moderate<br />
| Moderate<br />
| Low<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
| Intermediate<br />
| High<br />
| Low<br />
| Low<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|High<br />
| Moderate<br />
|Moderate<br />
|High<br />
|-<br />
<br />
|Decrease in salinity<br />
|Intermediate<br />
|High<br />
|Low<br />
|Low<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Intermediate<br />
|High<br />
|Low<br />
|Very low<br />
|}<br />
<br />
</br><br />
===='''''Mytilus spp.'''''====<br />
<br />
Seed and Suchanek (1992)<ref name= "Suchanek"/> suggested that although mussel assemblages found in the upper intertidal or most sheltered sites experience the least change per unit time and may be considered more 'stable' (Lewis, 1977<ref>Lewis, 1977: The role of physical and biological factors in the distribution and stability of rocky shore communities Lewis, J.R. (1977). The role of physical and biological factors in the distribution and stability of rocky shore communities. '''In''': Keegan, B.F. ''et al''. (Ed.) (1977). Biology of Benthic Organisms: ''11th European Symposium on Marine Biology'', Galway, 1976. pp. 417-424.</ref>), these assemblages would recover much slower than lower intertidal and more exposed sites if disturbed. In addition, ''Mytilus'' spp. recovers quicker than other ''Mytilus'' species (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Overall, ''Mytilus'' spp. populations are considered to have a strong ability to recover from environmental disturbances (Table 3, Holt ''et al.'', 1998<ref name= " Holt98 "/>; Seed and Suchanek, 1992). Larval supply and settlement could potentially occur annually, but settlement is sporadic with unpredictable pulses of recruitment (Lutz and Kennish, 1992<ref>LUTZ R.A., & KENNISH M.J., 1992. Ecology and morphology of larval and early postlarval mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 53‐86. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9202 www.vliz.be/imis].</ref>; Seed and Suchanek, 1992<ref name= "Suchanek"/>). Therefore, while good annual recruitment is possible, recovery may take at least 5 years, although in certain circumstances and under some environmental conditions, recovery may take significantly longer (Tyler‐Walters, 2008<ref name= "Tyler">TYLER-WALTERS H., 2008. ''Mytilus edulis''. Common mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on‐line]. Plymouth: ''Marine Biological Association of the United Kingdom''. More info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3848 www.marlin.ac.uk].</ref>).<br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 3: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''Mytilus spp.''. Level of confidence is included to give an indication of literature available on each factor. (Source: see [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Low<br />
|Very high<br />
|Very low<br />
|High<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| High<br />
| Moderate<br />
| High<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Decrease in emergence<br />
|Low<br />
|Very high<br />
|Very low<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|-<br />
<br />
|Increase in turbidity<br />
| Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
| Not relevant<br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Noise<br />
|Tolerant*<br />
|Not relevant<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate<br />
|-<br />
<br />
|Displacement<br />
|Intermediate<br />
|High<br />
|Low<br />
|Moderate <br />
|-<br />
<br />
|Decrease in salinity<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate <br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|High <br />
|}<br />
<br />
</br><br />
===='''''Modiolus modiolus'''''====<br />
<br />
''M. modiolus'' is a long‐lived species and individuals are commonly observed to be older than 25 years. This species is regarded to be intolerant of loss of substratum, physical damage and abrasion (Table 4). Recovery is thought to take many years due to sporadic recruitment (Tyler-Walters, 2007<ref name= "Tyler07">TYLER-WALTERS H., 2007. ''Modiolus modiolus''. Horse mussel. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. [cited 01/05/2011]. more info: [http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3817 www.marlin.ac.uk].</ref>). <br />
<br />
''M. modiolus'' individuals or reefs are generally not considered to be fragile, however, physical threats from fishing gears pose a significant threat to this species. Older individuals are susceptible to boring by the sponge ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=134121 Clione celata]'' which can make shells brittle, thus increasing vulnerability (Comely, 1978<ref>COMELY C.A. 1978. ''Modiolus modiolus'' (L.) from the Scottish west coast. ''Ophelia''. '''17''', 167-193.</ref>). <br />
<br />
{| border="1" cellspacing="0" width="600px" style="margin: 1em auto 1em auto;"<br />
|+ <span style="Font-size: 120%">'''Table 4: List of levels of “intolerance”, “recoverability” and “sensitivity” for physical and chemical threats to ''M. modiolus''. Level of confidence is included to give an indication of literature available on each factor. (Source: See [http://www.marlin.ac.uk www.marlin.ac.uk Marlin website] for primary sources).'''</span><br />
|-<br />
! bgcolor="silver" |Factor<br />
! bgcolor="silver" |Intolerance<br />
! bgcolor="silver" |Recoverability<br />
! bgcolor="silver" |Sensitivity<br />
! bgcolor="silver" |Confidence<br />
|-<br />
|Increase in temperature<br />
|Intermediate<br />
|Low<br />
|High <br />
| Very low<br />
|-<br />
<br />
|Substratum loss<br />
| High<br />
| Low<br />
| High<br />
| Moderate<br />
|-<br />
<br />
|Increase in suspended sediment<br />
| Low<br />
|Immediate<br />
|Not sensitive<br />
|Low<br />
|-<br />
<br />
|Increase in water flow rate<br />
|Intermediate<br />
|Low<br />
|High<br />
|Low <br />
|-<br />
<br />
|Increase in turbidity<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Moderate <br />
|-<br />
<br />
|Increase in wave exposure<br />
|Intermediate<br />
|Low<br />
|High<br />
|Very low<br />
|-<br />
<br />
|Noise<br />
|Tolerant<br />
|Not relevant<br />
|Not sensitive<br />
|High<br />
|-<br />
<br />
|Abrasion & physical disturbance<br />
|High<br />
|Low<br />
|High<br />
|Low<br />
|-<br />
<br />
|Displacement<br />
|Low<br />
|Very high<br />
|Very Low<br />
|Very low <br />
|-<br />
<br />
|Decrease in salinity<br />
|High<br />
|Low<br />
|High<br />
|Moderate<br />
|-<br />
<br />
|Changes in oxygenation<br />
|Low<br />
|Very high<br />
|Very low<br />
|Moderate<br />
|}<br />
<br />
</br><br />
===NATURAL AND ANTHROPOGENIC THREAT===<br />
<br />
These organisms are exposed to a broad range of threats; therefore not all are discussed in this section. The most severe threats have been given priority (physical, chemical and biological), with particular emphasis on those relating to floods and storms. <br />
<br />
Physical threats can originate from natural and [[anthropogenic]] sources. Natural sources include increased temperatures, an increase in storm occurrence and intensity and sea‐level rise, all of which occurre as a result of global [[climate change]]. In this section we holistically address the general physical pressures each species faces, rather than those from individual processes. Physical anthropogenic threats to reefs are extensive, so not all are covered in this document. Some of the major threats to natural reefs are the impact of fishing gears, marine aggregate extraction, coastal development (including the construction of coastal defences), construction of offshore marine renewable and oil and gas exploration. Natural chemical threats posed by climate change include reduced [[salinity]], brought about by increased precipitation and surface runoff, and acidification brought about by reduced pH and changes in oxygen concentrations. Anthropogenic chemical threats are primarily those associated with pollution. Biological threats are usually considered to be natural in the form of parasites, predators and competitors. However, invasion by non‐native species is often a result of human introduction and therefore can indirectly be considered an anthropogenic threat.<br />
<br />
</br><br />
===='''''Sabellaria spinulosa'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria spinulosa'' usually occurs subtidally in areas of high water flow, and is relatively tolerant of wave and tidal‐forcing. However, as ''S. spinulosa'' generally grows upon cobbles and pebbles (Connor ''et al.'', 2004<ref>CONNOR D.W., ALLEN J.H., GOLDING N., HOWELL K.L. LIEBERKNECHT L.M., NORTHEN K.O. & REKER J.B., 2004. The Marine Habitat Classification for Britain and Ireland. Version 04.05 (internet version: [http://www.jncc.gov.uk/MarineHabitatClassification www.jncc.gov.uk]). Joint Nature Conservation Committee, Peterborough. Also available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=201410 www.vliz.be/imis].</ref>), and since it has been suggested that an increase in wave or tidal flow may reduce the stability of the attachment substratum, this can result in increased scouring and mortality of individuals (Jackson and Hiscock, 2008<ref name= "Jackson 08">JACKSON A. & HISCOCK K., 2008. ''Sabellaria spinulosa''. Ross worm. Marine Life Information Network: Biology and Sensitivity Key Information Sub‐programme [on-line]. Plymouth: ''Marine Biological Association of the United Kingdom''. Available from: [http://www.marlin.ac.uk/species/Sabspi.htm www.marlin.ac.uk].</ref>). It is a relatively disturbance‐tolerant species and is often the first species to recolonise an area after a physical disturbance (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). The physical disturbance of removal from tubes and substratum loss will cause mortality. As ''S. spinulosa'' is predominantly subtidal, it is likely to be less affected by temperature changes than the intertidal ''S. alveolata'', which has been shown to be severely affected by low winter temperatures (Crisp, 1964<ref name= "Crisp">CRISP D.J. 1964. The effects of the severe winter of 1962‐63 on marine life in Britain. ''Journal of Animal Ecology''. '''33''', 165‐210.</ref>). Fisheries for the pink shrimp (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107651 Pandalus montagui]'') and brown shrimps (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=107552 Crangon crangon]'') (often associated with areas of ''Sabellaria spinulosa'' reefs) have been implicated in the loss or damage of reefs. However, Vorberg (2000)<ref name= " Vorberg "/> undertook experimental and observational studies that indicated only minor damage to tubes and rapid recovery as a result of shrimp fisheries. Nevertheless, populations, especially loose aggregations, may be displaced by mobile fishing gear. <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is little data available on chemical threats to ''S. spinulosa'', although it is not thought to be sensitive to reduced salinity (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). <br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is insufficient information available on biological threats to ''S. spinulosa''.<br />
<br />
</br><br />
===='''''Sabellaria alveolata'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
<br />
''Sabellaria alveolata'' is typically found in the intertidal and is tolerant of changes in sediment regime. The physical disturbance of removal from tubes and substratum loss will cause mortality. Being an intertidal species, the greatest threats come from cold air temperatures and heavy wave action. It has been suggested that most colonies die through eventual break up by wave action (Jackson and Hiscock, 2008<ref name= "Jackson 08"/>). Increased exposure will result in a potentially shorter colony life. ''S. alveolata'' is a southern species and is at the northern end of its range in Britain. This species is known to be negatively affected by extremely cold winters. In the cold winter of 1962/1963, ''S. alveolata'' suffered severe mortalities along the Welsh and southern English coastlines, where it had previously reached its northern and northeastern range limits (Crisp, 1964<ref name= "Crisp">). Populations suffered mortalities again during the winter of 1978/1979, but on a much smaller scale (Kendall and Bedford, 1987<ref>KENDALL M.A., & BEDFORD M.L., 1987. Reproduction and recruitment in the barnacle ''Chthamalus montaguiat Aberystwyth (mid-Wales). ''Marine Ecology Progress Series''. '''38''', 305-308.</ref>). Recent work by Mieszkowska ''et al.'' (2006)<ref>MIESZKOWSKA N., KENDALL M.A., HAWKINS S.J., Leaper R., Williamson P., Hardman-Mountford N.J., SOUTHWARD A.J., 2006. Changes in the range of some common rocky shore species in Britain - a response to climate change? ''Hydrobiologia''. '''555''', 241‐51. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=101367 www.vliz.be/imis].</ref> showed that ''S. alveolata'' had recolonized locations close to their northern range limits from where they were lost after the cold winter of 1962/1963. Despite the current trends in global warming, winter 2009/2010 was the coldest on record in Europe, which may have negatively affected ''S. alveolata'' at its range edges. Continued monitoring is necessary to detect future changes.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
<br />
There is insufficient information available on chemical threats to ''S. alveolata''.<br />
<br />
</br><br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
<br />
There is very little information available on the biological threats to ''S. alveolata''. In a recent study of ''S. alveolata'' reefs in the Bay of Mont San‐Michel, France found that reefs were becoming increasingly colonized by the invasive Pacific oyster ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=140656 Crassostrea gigas]'' from local aquaculture operations and by green algae (''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=144296 Ulva]'' spp.) due to the increasing inputs of nitrates from terrestrial origin (Dubois ''et al.'', 2006<ref name="Dubois">DUBOIS S., COMMITO J.A., OLIVIER F., & RETIERE C., 2006. Effects of epibionts on ''Sabellaria alveolata'' (L.) biogenic reefs and their associated fauna in the Bay of Mont Saint-Michel. ''Estuarine, Coastal and Shelf Science''. '''68''', 635‐646.</ref>). It was found that epibionts, especially green algae, alter ''S. alveolata'' population structure, causing a reduction in new recruits that in the long run may cause significant damage to the reef structure itself. Furthermore, Dubois ''et al''. (2006)<ref name="Dubois"/> noted that ''C. gigas'' have high filtration rates, suggesting that they may out-compete ''S. alveolata'' for food.<br />
<br />
Competition for space with common mussels ''Mytilus'' spp. occurs, especially on boulder scars, but the factors influencing this are unknown. Heavy settlement of mussels on ''S. alveolata'' reefs has been suspected of causing short term destabilization and loss of habitat (Tyler -Walters, 2008<ref name= "Tyler"/>). <br />
<br />
</br><br />
====''''' Mytilus spp.'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''Mytilus'' spp. can be found both intertidally and subtidally. It is a fairly tolerant species with the biggest threats posed by habitat loss and dislodgement by storms. Removal of the substratum, be it rock or sediment, will entail removal of the entire population and its associated community. Repeated substratum loss and recruitment result in a patchy distribution of mussels on the shore (Seed and Suchanek, 1992<ref name= "Suchanek"/>). Storms and tidal surges are known to destroy mussel beds, often over hundreds of hectares in the Wash, Morecambe Bay and the Wadden Sea. With increasing wave exposure, mussel beds become increasingly patchy and dynamic. ''Mytilus'' spp. beds may also be damaged by wave driven logs or equivalent debris (Seed and Suchanek, 1992<ref name= "Suchanek">). Trampling by human traffic is most likely in spring and summer (Brosnan and Crumrine, 1994<ref>BROSNAN D.M., & CRUMRINE L.L., 1994. Effects of human trampling on marine rocky shore communities. ''Journal of Experimental Marine Biology and Ecology''. '''177''', 79-97. </ref>). The combined effects of trampling and natural winter disturbances may result in loss of mussel beds in the long term. Displacement and or dislodgement by storms will likely lead to mortality. Dare (1976)<ref name= "Dare"/> found that individual mussels swept or displaced rarely survived, since they either became buried in sand or mud, or were scattered and eaten by oystercatchers. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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In general, ''Mytilus'' spp. is tolerant of a wide range of contaminants and salinity and oxygen fluctuations. The most significant natural chemical threat to ''Mytilus'' spp. is a reduction in salinity caused by storm runoff (Hiscock pers. Comm. in Tyler-Walters 2008<ref name= "Tyler"/>). The effects of contaminants on ''Mytilus'' sp. were extensively reviewed by Widdows and Donkin (1992)<ref name= "Widdows">WIDDOWS J., & DONKIN P., 1992. Mussels and environmental contaminants: bioaccumulation and physiological aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp.383‐424.</ref> and Livingstone and Pipe (1992)<ref>LIVINGSTONE D.R., & PIPE R.K., 1992. Mussels and environmental contaminants: molecular and cellular aspects. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier Press, Amsterdam: pp. 425-510.</ref>. Mussels are suspension feeders and therefore process large volumes of water together with suspended particulates and phytoplankton. Mussels absorb contaminants directly from the water, through their diet and via suspended particulate matter (Widdows and Donkin, 1992)<ref name= "Widdows"/>, the exact pathway is dependant on the nature of the contaminant. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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''Mytilus'' spp. host a wide variety of disease organisms, parasites and commensals from many animal and plant groups including bacteria, blue green algae, green algae, protozoa, boring sponges, boring polychaetes, boring lichen, the intermediary life stages of several trematodes, copepods and decapods (Bower, 1992<ref>BOWER S.M., 1992. Diseases and parasites of mussels. '''In''': Gosling, E. (Ed.). The mussel ''Mytilus'': ecology, physiology, genetics and culture. Developments in Aquaculture and Fisheries Science 25. Elsevier, Amsterdam: pp. 543‐563. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=9213 www.vliz.be/imis].</ref>; Gray ''et al.'', 1999<ref>GRAY A.P., LUCAS I.A.N., SEED R., and RICHARDSON C.A., 1999 ''Mytilus edulis chilensis'' infested with ''Coccomyxa parasitica'' (''Chlorococcales'', ''Coccomyxaceae''). ''Journal of Molluscan Studies''. '''65''', 289-294.</ref>). ''Mytilus'' spp. is threatened by a number of invasive species. ''Aulocomya ater'', a mytilid, native to South America has been reported in the Moray Firth, Scotland in 1994 and again in 1997 (Holt ''et al.'', 1998<ref name= " Holt98 "/>; Eno ''et al.'', 2000; McKay, 1994<ref>MCKAY D., 1994. Unravelling the choreography of contaminant kinetics: approaches to quantifying the uptake of chemicals by organisms. In: J.L. Hamelink, P.F. Landrum, H.L. Bergman and W.H. Benson (Editors), Bioavailability: Physical, Chemical, and Biological Interactions, Lewis Publisher Inc., Chelsea, MI., pp. 17l‐l77.</ref>). ''A. Ater'' is thought to have a stronger byssal attachment than ''Mytilus'' spp. and can replace ''Mytilus'' spp. in more exposed areas if it reproduces successfully (Holt ''et al.'', 1998<ref name= " Holt98 "/>). <br />
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The Pacific oyster ''Crassostrea gigas'' was introduced in Europe for commercial purposes in the mid 1960s. In Europe, wild populations of Pacific oysters are already found from northern Germany to southern Portugal. Fey ''et al.'' (2010)<ref>FEY F., DANKER N., STEENBERGEN J., & GOUDSWAARD K., 2010. Development and distribution of the non-indigenous Pacific oyster (''Crassostrea gigas'') in the Dutch Wadden Sea. ''Aquaculture International''. '''18(1)''', 45‐59. Available form: [http://www.vliz.be/imis/imis.php?module=ref&refid=145408 www.vliz.be/imis].</ref> found that many mussel beds (''Mytilus'' spp.) have been taken over by Pacific oysters in the Dutch Wadden Sea. In the German Wadden Sea almost all mussel beds are now considered oyster reefs (Nehls ''et al.'', 2006<ref>NEHLS G., DIEDERICH S., THIELTGES D., & STRASSER M., 2006. Wadden Sea mussel beds invaded by oysters and slipper limpets: competition or climate control? ''Helgoland Marine Research''. '''60''', 135‐143. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=100432 www.vliz.be/imis].</ref>; Wehrmann ''et al.'', 2007<ref>WEHRMANN A, MARKERT A, SCHMIDT A., 2007 Miesmuschelbank: ein verlorener Lebensraum? ''Die Einwanderung der Pazifischen Auster in das Wattenmeer und ihre Folgen. Natur- und Umweltschutz''. '''6(1)''', 10–14.</ref>). In the early stage of the development of ''C. gigas'', Reise (1998) found 85% attached to ''Mytilus'' spp. (alive and empty shell) and 8% on other bivalves. <br />
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The American slipper limpet ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=138963 Crepidula fornicata]'', native to the North American East coast, was unintentionally introduced to Europe by oyster farming in the 1870s and now occurs from Denmark to Spain, Norway, the Mediterranean, Ireland and the United Kingdom (Blanchard, 1997<ref>BLANCHARD M., 1997. Spread of the slipper‐limpet (''Crepidula fornicata'') in Europe. Current state and consequences. ''Scientia Marina''.''61(2 sup.)'', 109-118. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208711 www.vliz.be/imis].</ref>; Thieltges ''et al.'', 2003<ref>THIELTGES D.W., STRASSER M., REISE K., 2003. The American slipper limpet ''Crepidula fornicate (L.)'' in the northern Wadden Sea 70 years after its introduction. ''Helgoland Marine Research''. '''57''', 27-33.</ref>; Rayment, 2007). There are conflicting results in the literature on the effects of ''C. fornicate'' on ''Mytilus'' spp.. In one set of field experiments (Thieltges, 2005<ref name= "Thieltges05">THIELTGES D.W., 2005a. Impact of an invader: epizootic American slipper limpet Crepidula fornicate reduces survival and growth in European mussels. ''Marine Ecology Progress Series''. '''286''',13-19.</br>'''AND'''</br> THIELTGES D.W., 2005b. Benefit from an invader: American slipper limpet ''Crepidula fornicate'' reduces star fish predation on basibiont European mussels. ''Hydrobiologia''. '''541(1)''', 241‐244. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=208713 www.vliz.be/imis].</ref>), the presence of ''C. fornicate'' has been shown to cause a reduction in survival and growth of the blue mussel ''Mytilus'' spp.. A reduction in survival and growth of mussels was likely due to physical interference, associated with the attachment of ''C. fornicata''. It is probable that when attachment onto a host occurs, the host organism will experience greater drag forces, requiring them to use more energy to remain attached to the substrate. This extra energetic requirement may result in reduced fecundity and survivability. Conversely, ''C. fornicate'' have also been found to benefit ''Mytilus'' spp. Work done by the same authors, Thieltges (2005<ref name= "Thieltges05"/>) found that ''C. fornicate'' presence on mussels led to a three‐fold decrease in predation by starfish. Although starfish did not prey directly on ''C. fornicate'', it is believed that the cover provided by settled limpets made it more difficult for the starfish to prey on the mussels. <br />
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====''''' Modiolus modiolus'''''====<br />
<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Physical threats'''</span></br><br />
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''M. modiolus'' is thought to have an intermediate to high intolerance to physical disturbance (Tyler-Walters, 2008<ref name= "Tyler"/> and 2007<ref name= "Tyler07"/> respectively). Subtidal ''M. modiolus'' beds are susceptible to damage from fishing activities. In Strangford Lough, Northern Ireland, ''M. modiolus'' beds have been shown to suffer damage and mortality by scallop [[dredging]] (Service and Magorrian, 1997<ref>SERVICE M., MAGORRIAN B. H., 1997. The extent and temporal variation of disturbance of epibenthic communities in Strangford Lough, Northern Ireland. ''Journal of the Marine Biological Association of the United Kingdom''. '''77''', 1151‐1164.</ref>; Magorrian and Service, 1998<ref>MAGORRIAN B.H., & Service, M., 1998. Analysis of underwater visual data to identify the impact of physical disturbance on horse mussel (''Modiolus modiolus'') beds. ''Marine Pollution Bulletin''. '''36''', 354-359.</ref>). <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Chemical threats'''</span></br><br />
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There is insufficient information available on chemical threats to ''M. modiolus''. <br />
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<span style="Font-size: 115%"; span style="color:#5F9EA0">'''Biological threats'''</span></br><br />
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Predation by crabs and starfish presents one of the greatest threats to juvenile ''M. modiolus'' (Brown and Seed, 1977<ref>BROWN R.A. & SEED R., 1977. ''Modiolus modiolus'' (L.) - an autecological study. '''In''': KEEGAN B.F., O'CEIDIGH P., BOADEN P.J.S. (eds). Biology of Benthic Organisms. Proceedings of the 11th European Symposium on Marine Biology, Pergamon Press, Oxford, Galway, Ireland, pp 93‐100. Available from: [http://www.vliz.be/imis/imis.php?module=ref&refid=27846 www.vliz.be/imis].</ref>; Anwar ''et al.'', 1990<ref name= " Anwar "/>; Tyler-Walters, 2007<ref name= "Tyler07"/>). As mussels grow and become more difficult to open, the threat of predation becomes less important (Seed and Brown, 1977<ref name= "Seed77"/>). High densities of the brittle star, ''[http://www.marinespecies.org/aphia.php?p=taxdetails&id=125131 Ophiothrix fragilis]'', are considered to be capable of having a detrimental effect on ''M. modiolus'' beds not only through removal of both food and mussel larvae from the water column (George and Warwick, 1985<ref name= "George"/>; Holt ''et al.'', 1998<ref name= "Holt98"/>). <br />
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===KEY PROCESSES TO FOCUS ON FOR MAINTAINING ECOSYSTEMS INTEGRITY===<br />
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In this section we discuss the processes to focus on for maintaining ecosystems integrity in terms of reefs in general and will not go into details for each species. <br />
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The spatial and temporal distribution of biogenic reefs can vary on vary small scales (i.e. meters and days) (Foster‐Smith, 2000<ref>FOSTER‐SMITH R.L., 2000. Establishing a monitoring baseline for the Wash subtidal sandbanks. pp 51.</ref>; Foster-Smith and White, 2001) making it difficult to accurately assess their status using point sampling methods. The ephemeral and unpredictable nature of biogenic reefs poses a challenge to effective management. The establishment of designated sites to protect habitats relies on a certain level of stability. Unless conservation effort can be concentrated on reefs of proven stability, site designation for biogenic reefs can prove unsuccessful. <br />
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Hendrick ''et al.'' (2011)<ref name= "Hendrick">HENDRICK V. J., FOSTER‐SMITH R. L. & DAVIES A. J., 2011. Biogenic Reefs and the Marine Aggregate Industry. Marine ALSF Science Monograph Series No. 3. MEPF 10/P149. (Edited by R. C. NEWELL & J. MEASURES). 60pp. ISBN: 978 0 907545 46 0.</ref> suggest the designation of a much broader site comprising areas which already support dense populations or are considered suitable for potential biogenic reef development may be more beneficial. This approach is analogous to the protection of mobile species rather than habitats or sessile species, affording protection of the environmental condition and mechanisms which enable biogenic reefs to develop. An alternative approach, suggested by Hendrick ''et al.'' (2011)<ref name= "Hendrick"/>, is the smaller-scale conservation of specific reef sites, with the view to the designation status lasting only for the lifetime of the actual reef. In order for this approach to be effective, the designation procedure must act on a shorter time scale (months rather than years). <br />
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Ideally, a combination of the two above mentioned approaches would prove to be the most effective. This would involve regular mapping of biogenic reefs within a larger supporting boundary. Exclusion zones around the reefs could be established and managed. <br />
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===CURRENT MANAGEMENT PRACTICES===<br />
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Biodiversity is of immense interest for managers and policy-makers. As such, The United Nations declared 2010 the International Year of Biodiversity (Resolution 61/203). Throughout the course of the year events will take place world-wide to raise public awareness of not only the biological diversity on our planet, but the importance of protecting it. The origins of legal mechanisms and targets for protecting biodiversity mostly stem from the Convention on Biological Diversity (CBD) that was drawn up in 1992. Parallel to the CBD, the European Community (EC) adopted the Council Directive 92/43/EEC in 1992, this legalization became more commonly known as the Habitats Directive. The directive focused on the conservation of natural habitats and of wild fauna and flora through the establishment of a network of Special Areas of Conservation (SACs). The primary objective of which, is to promote the safeguarding and preservation of threatened species and habitats deemed to be of European importance. <br />
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In response to the CBD, the UK Government also founded the UK Biodiversity Partnership to develop and implement UK Biodiversity Action Plans (UK BAP). UK BAP recognizes threatened biological assets within the UK and its surrounding waters and presents policies for the management and conservation of these assets. Plans for species and habitats in danger have been established to aid in recovery in order to assist in the UK’s development in reducing biodiversity loss set out in the CBD ([http://jncc.defra.gov.uk/page-1817 UK Biodiversity Group], 1999). To date, it has lead to the construction of action plans for 1150 priority species and 65 priority habitats ([http://jncc.defra.gov.uk/page-5700 BRIG, 2007]]). Reefs are one of the habitats listed under Annex I of the Habitats Directive which require the designation of an SAC.<br />
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===='''''Sabellaria spinulosa'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub-features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention ([[OSPAR]]) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation.<br />
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===='''''Sabellaria alveolata'''''====<br />
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Intertidal protection for ''S. alveolata'' reefs can be achieved through SSSI designation. ''S. alveolata'' reefs also occur as sub‐features of non‐reef Annex 1 habitats (eg intertidal mudflats and sandflats) under the Habitats Directive and are present in a number of candidate Special Areas of Conservation (cSACs). Discharges to the sea are controlled by a number of EC Directives, including the Dangerous Substances, Shellfish (Waters), Integrated Pollution Control, Urban Waste Water Treatment, and Bathing Waters Directives. The forthcoming Water Framework Directive will also be relevant. The Oslo and Paris Convention (OSPAR) and North Sea Conference declarations are also important. These commitments provide powers to regulate discharges to the sea and have set targets and quality standards to marine waters. An extensive set of standards covering many metals, pesticides and other toxic, persistent and bioaccumulative substances, and nutrients have been set under UK legislation. <br />
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===='''''Mytilus spp.'''''====<br />
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Alhough ''Mytilus'' spp. is not designated under any protection laws, the habitat “Intertidal ''Mytilus'' spp. beds on mixed and sandy sediments” has been listed on the OSPAR List of Threatened and/or Declining Species and Habitats. ''Mytilus'' spp. is also protected by fisheries regulations. Fisheries regulations vary greatly in different parts of the Europe. The regulatory considerations in terms of mussel fisheries management are complex.<br />
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===='''''Modiolus modiolus'''''====<br />
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In addition to its listing by OSPAR, this habitat is the subject of several local, national and regional listings, including the Habitats Directive (as part of ‘Reefs’) and the UK Biodiversity Action Plan. Such listings serve to highlight the conservation needs of the habitat, but successful protection depends on specific actions that follow. In the UK M. modiolus beds are identified as features for protection in SACs (Special Areas of Conservation) off Scotland, Wales and Northern Ireland.<br />
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== SEE ALSO ==<br />
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[http://www.theseusproject.eu/index.php?option=com_remository&Itemid=2&func=select&id=41 Theseus Official Deliverable 3.3-Natural habitats for coastal protection and relevant multi-stressor coastal risks. Report and European Scale overview.]<br />
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[[Natural_barriers#Biogenic_reefs |Natural barriers, Biogenic reefs]]<br />
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[[Biogenic_reefs_of_Europe_and_temporal_variability | Biogenic reefs of Europe and temporal variability]]<br />
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==REFERENCES ==<br />
<references/><br />
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[[Category: Marine habitats and ecosystems]]<br />
[[Category: Biodiversity and habitat loss]]<br />
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{{ 5Authors<br />
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|AuthorFullName1= Firth, Louise<br />
|AuthorID2=25628<br />
|AuthorFullName2= Davies, Andrew<br />
|AuthorID3=?<br />
|AuthorFullName3=Hawkins, Stephan<br />
|AuthorID4=12778<br />
|AuthorFullName4= Airoldi, Laura<br />
|AuthorID5=206666<br />
|AuthorFullName5= Colangelo, Marina Antonia<br />
}}</div>Katreineblomme