Theme III: The structure of the benthic system

Abstract

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 macroand microphytobenthos as well as the consumption by infauna predators may also be important energy pathways . This section deals mainly with some structural aspects of the benthic system and possible effects caused by the changed environmental conditions in the Oosterschelde after the construction of a storm-surge barrier and secondary dams . Within the benthic system of the Oosterschelde a distinction must be made between two very different benthic habitats: hard and soft bottoms . The seawalls and many other constructions provide an artificial area of hard substrate, estimated at about 1150 ha in the Oosterschelde (Smaal & Boeije, 1991) . The benthic communities on these hard substrates in the Oosterschelde estuary were known to be very rich and are covered in this section by the papers of De Kluijver & Leewis (1994) and Meijer & Waardenburg (1994) for the sublittoral and littoral zone respectively . The results between both studies differ however strikingly . In the littoral zone the environmental changes did not seem to have affected the communities strongly . The reduction in tidal amplitude had a minor effect on the zonation of communities. Especially in the upper part of the 153