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The edible cockle (Cerastoderma edule L.) is a dominant suspension feeder in the Oosterschelde, a 351 km2 tidal bay in the SW Netherlands. To establish its role in the benthic foodweb, and to assess the impact of human activities, data on density, age composition, biomass and growth were collected from several tidal flats in the Oosterschelde between 1980 and 1990.

The construction of a storm-surge barrier in the mouth of the Oosterschelde caused important hydrodynamical and morphological changes that could influence the macrobenthic populations. This paper is one in a series of five all dealing with the effects of the storm-surge barrier on macrozoobenthos and analyses the spatial and temporal distribution of macrozoobenthos in the Oosterschelde and its relationship with some environmental parameters, based on two large scale sampling campaigns, one before and one after the completion of the barrier.

The benthic compartment forms a very important link within the estuarine ecosystem. It depends to a large extent on the import of food (plankton or detritus) from the pelagic system, and it serves as food for many predators, of which fish and birds are best known. However, both the primary production within the benthic compartment by macro- and microphytobenthos as well as the consumption by infauna predators may also be important energy pathways.

Between 1982 and 1987, the construction of a storm-surge barrier and two secondary dams in the eastern and northern parts of the Oosterschelde/Krammer-Volkerak area resulted in the loss of 33% of the 170 km2 of intertidal area in the estuary. Consequences for non-breeding waterbirds were evaluated on the basis of monthly high-tide counts during five seasons before and three seasons after the construction period.

To evaluate the effects of the construction of a storm surge barrier in the Oosterschelde, long-term patterns (1979–89) in abundance and biomass of the intertidal macrozoobenthos were studied at 14 permanent stations. Additionally, data of a large-scale survey in late summer 1985 and 1989 were analysed. In this paper, patterns in general parameters are discussed.

In order to evaluate the impact of the construction of the storm-surge barrier and secondary dams on macrobenthos of the tidal flats in the Oosterschelde (SW Netherlands), changes in distribution, density and biomass of five common species (Spio martinensis, Hydrobia ulvae, Arenicola marina, Scoloplos armiger and Bathyporeia sp) were analysed.