View source for Biogenic reefs of Europe and temporal variability

== European-scale distribution of biogenic reefs==
[[Image:coastal and shelf habitats.jpg|thumb|right|250px|Figure 1: Map taken from the OSPAR Status Report 2010 depicting the distribution of the threatened and/or declining coastal and shelf habitats in Europe.]]

Biogenic reefs can be described as hard compact structures created by the activity of living organisms. They do not share a 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: ''Sabellaria alveolata'', ''Sabellaria spinulosa'', ''Modiolus modiolus'' and ''Mytilus edulis''. Many biogenic reef 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] </ref>). Figure 1 illustrates the distribution of some biogenic reef habitats which are currently in decline around the coast of Europe. </br>

'''''Sabellaria spinulosa'''''

''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" />, Fig. 2.20). 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]</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 & 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 1). 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 & 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, 8m 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"/>). 


'''''Sabellaria alveolata'''''



==Examples==




 [[Natural_barriers#Biogenic reefs| based on]]

==References==
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