M I D A S
Marine Information and Data Acquisition System
Campaign :The Abra alba/Mysella bidentata community on BCS  (Lookup in IMIS)
Abstract:
Because of the high ecological value of parts of the Belgian Continental Shelf (BCS), combined with increasing anthropogenic pressure on the marine ecosystem, the establishment of marine protected areas (MPA’s) is of high priority within the current policy. Biological information is essential to be able to set up a scientifically justified management. Since indicators (Feral, 1999) allow to describe the environment on a time- and cost efficient way, they represent useful tools within the monitoring of the management. So far, the Abra alba – Mysella bidentata community is the most diverse and dense macrobenthic community of the BCS. The ‘riff’ building polychaet Lanice conchilega performs an important habitat structuring function within the community, with a possible subsequent increase of densities and diversity. Abra alba and Spisula subtruncata, two characteristic and abundant bivalves of the community, are important food resources for higher trophic levels, such as demersal fishes and seabirds. Scientifically justified management and monitoring of this ecologically valuable Abra alba – Mysella bidentata community is of highest importance. At first, detailed knowledge on the ecology of the community is needed (e.g. spatial and temporal patterns). Secondly, the population dynamics of ecological important species (such as Lanice conchilega, Spisula subtruncata and Abra alba) has to be evaluated, considering their use as indicators for a time- and cost efficient monitoring of the community. The spatial distribution of the community and its habitat preferences will be studied. Special attention will be paid to the community structure (e.g. diversity, density, biomass and trophic interactions) along physico-chemical gradients (Western – Eastern coastal zone, onshore - offshore). This will be done by means of (1) the collection of new macrobenthic data within unstudied parts of the BCS and (2) detailed literature and data research on the macrobenthos of the BCS. Temporal variability in the community structure will be studied on short (seasonal), medium (year-to-year) and long (’70 versus ’90) term and this along physico-chemical gradients. Therefore, macrobenthic samples will be collected monthly (March 2002 to October 2003) at different zones of the BCS (Western Coastal banks, Eastern coastal zone and an offshore area). During the period of major recruitment (May and June) samples will be collected every two weeks. Data obtained will be compared with data available from previous studies (’70 versus ’90). The study of the population dynamics of ecological important species in relation to their environment is indispensable to evaluate their use in monitoring. Macrobenthic, meiobenthic and plankton samples will therefore be collected at the same places and during the same period as indicated for the temporal study. Comparing zones with and without Lanice ‘riffs’, the habitat and community structuring capacity of Lanice conchilega will be studied in detail. The sediment catching capacity of the Lanice ’riffs’ will be tested experimentally. Knowledge of the spatial and temporal patterns in the Abra alba – Mysella bidentata community will be used to formulate advices for a scientifically justified management and monitoring of this ecologically valuable community. Furthermore, the use and value of the ecological important species studied as possible indicators will be evaluated.