The response of benthic suspension feeders to environmental changes

Abstract

In many estuaries, benthic suspension feeders generally occur in high densities and biomass, often concentrated in beds and reefs. In the Oosterschelde estuary the main species are cockles (Cerastoderma edule), mussels (Mytilus edulis) and the (subtidal) rocky shore populations of e.g. oysters (Crassostrea gigas), Ascidians, sponges and brittle stars (Ophiothrix fragilis). Biomass, averaged over the whole area in the post-barrier period, was estimated for cockles, mussels and rocky shore populations as 13.1, 10.7 and 2.5 g ash-free dry weight (AFDW) m ^{- 2}, respectively (Smaal & Nienhuis, 1992). In comparison with the mean biomass over the whole area of the other benthic populations (mainly deposit feeders) of 5 g AFDW m ^{- 2}, the dominance of the suspension feeders is obvious. Biomass data can also be presented per unit of habitat surface: in that case mean biomass of cockles and benthic deposit feeders on the tidal flats is 40 and 15 g AFDW m ^{- 2} respectively, mean mussel biomass on mussel cultivation plots is 170 g AFDW m ^{- 2} and mean biomass of the rocky shore community is 88 g AFDW per m ^{- 2} hard substrate (Seys et al., 1994; Leewis et al., 1994).