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|Hierarchical Monitoring Methods for Tidal Flats|
English title: Hierarchical Monitoring Methods for Tidal Flats
Reference no: OND1290730
Period: January 2002 till December 2005
Thesaurus terms: Intertidal environment; Man-induced effects; Monitoring
Geographical term: ANE, Netherlands, Westerschelde [Marine Regions]
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Intertidal and shallow subtidal soft sediment microbial communities play an important role in coastal biogeochemistry and provide ecosystem services that directly benefit the human population. These functions include processing of excess nutrients, provision of food sources for commercially important fish and shellfish species, and prevention of coastal erosion. Prediction and modelling the responses of coastal ecosystems, particularly soft sediment systems, to environmental change is inherently difficult. Microalgal biofilms on intertidal mudflats occur sporadically throughout the year, and have a patchy distribution. Periods of extremely high primary production and sediment stabilisation are interspersed with periods of low algal abundance. Sediment-dwelling microalgae exist in a dynamic environment, with steep and constantly varying, vertical gradients in sediment chemistry (e.g. pH) and physical conditions (irradiance). Cells at the surface may experience high light stress and they may be deprived of nutrients and CO2. These conditions make it difficult to predict and quantify the biomass and production of microalgae, which is a primary factor controlling the function of the sediment ecosystem, and which must be considered by managers of the coastal zone.
The objective of the HIMOM project is to provide a system of Hierarchical Monitoring Methods (HMM) to determine system change within intertidal areas. A standardised toolkit will be developed with which to characterise the key biological and physical processes in intertidal areas of estuaries. HIMOM will produce and implement the HMM in the form of handbooks and learning tools in order to provide coastal zone managers in the EU with a cost-effective management strategy. In the course of the project, techniques and methodology will be standardised and intercalibrated, with the input of expert knowledge from sedimentologists, biologists and end-users of the HMM at all steps. The objective of NIOO-MM within the project is to investigate dynamics in microalgal biomass and primary production and develop standardized optical methods within the HMM. These methods can be used in combination with remote sensing data to extrapolate from point measurements to the scale of whole estuaries. Approach Components of the HMM will be developed and field-tested by working closely together with the National Institute for Coastal Zone Management (RIKZ) in this project. Both partners will conduct synchronised sampling campaigns at the same times and locations. Biomass will be studied by both traditional means (wet sampling, RIKZ) and by optical measurements, using hyperspectral surface reflectance scans and fluorescence measurements (NIOO-MM). Cost-benefit analyses of the two methods will be performed. The Westerschelde estuary is the chosen study site. Regular airborne remote sensing flights will assist in the assessment of biomass and primary production at the scale of the entire estuary. Algorithms to estimate microphytobenthic biomass from remote sensing data will be further improved. Vertical changes in biomass that are caused by migration of diatoms will be measured using fiberoptic microprobes, in combination with surface reflectance, and incorporated into a model of sediment optical properties. Primary production will be studied using a suite of methods, in combination with (microfiber) PAM-fluorometry, and results will be combined with estimates of photosynthetically-active biomass in order to accurately predict primary production.
Towards an HMM The HIMOM project started in March 2002. One of the first products of the project is an online Methods Handbook that was completed in March 2003. Production of the Handbook was preceded by extensive intercalibration of methods during a workshop organised by NIOO-MM. Optical methods for measuring sediment characteristics were intercalibrated to ensure a high degree of repeatability between different instruments and operators, and are now in deployment at 5 European estuaries. The optical methods produced very similar estimates of microalgal biomass for a wide range of different sediment types, whereas pigment determinations varied considerably between laboratories. Estimation of benthic algal biomass and production The growth rates and carrying capacity of a developing microalgal biofilm were investigated with HiMOM methods in a mesocosm experiment together with project 00MM14: Quantifying PSII electron transport in microphytobenthos. A sampling program was carried out regularly on a number of intertidal sites, in combination with the standard sampling for the monitoring program MOVE from RIKZ, and the VLANEZO project 02MM20: biodiversity-productivity relationships of benthic diatoms along a salinity gradient. Results of the first year are being used to assess the extent of variability within the estuary in parameters such as primary production, pigment composition and species diversity. Ground truthing using contact cores with a defined depth, together with ground-level remote sensing has produced an extensive database for algorithm development. As a result, chlorophyll levels in the surface layers of the sediment can be predicted with a high degree of accuracy (r2> 0.8) for both sandy and muddy sites from measurements of reflected solar irradiance. This information will be used in the interpretation of airborne remote sensing imagery obtained in September 2002
The HMM concept will be developed further at an end-user meeting to be held at NIOO in late 2003. A demonstration of selected elements of the HMM in use at five European estuaries will be performed during May 2003. Results will be available in near real-time from all sites via an internet site, and end-users will be invited to watch the demonstration. Further remote sensing campaigns are planned, using a CASI scanner, digital video cameras and specialised vegetation index cameras. These surveys will be carried out by MD-RWS and by NIOO-MM and results will be used to create maps of estuarine habitats, 'ecotypes'. Results of on-going sampling campaigns will be synthesised and used to determine the relationship between benthic productivity and diversity along the salinity gradient in the Westerschelde.
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