The ebb tidal delta of the Grevelingen: a man-made nursery for flatfish?

In order to investigate the impact of the closure of the Grevelingen estuary on the benthic life and nursery function of its ebb tidal delta, a comparison was made between the present ebb tidal deltas of the Grevelingen and the Eastern Scheldt. Three groups of benthic animals were compared: macrobenthos, epibenthic animals (including demersal fish) and hyperbenthos. The ebb tidal delta of the Grevelingen is much richer for almost all animal groups discussed. The data suggest that this richness is a consequence of the changes that have occurred in the hydrodynamics since the closure of the Grevelingen estuary in 1971. The area now traps and retains mud, detritus, larvae of different groups of infaunal animals, larvae of epibenthic crustaceans, and eggs and larvae of fish. This change is reflected in the increased importance of the area as a nursery for flatfish, especially dab and sole. However, the increase in the nursery function of the ebb tidal delta does not make up for the loss of nursery areas in the estuary itself