THE EFFECTS OF MARINE GRAVEL EXTRACTION ON THE MACROBENTHOS - EARLY POST-DREDGING RECOLONIZATION

A small area of sea bed off the English east coast was experimentally dredged by a commercial suction-trailer dredger. Some 50 000 t of mixed aggregate were removed, representing about 70% of the sea bed area down to an average depth of 0.3 m. Results from benthic surveys undertaken at the experimental site and at a nearby reference site, indicate that significant reductions had occurred in the variety, abundance and biomass of benthic organisms as a consequence of dredging. Subsequent recolonization of dunuded substrates by the dominant taxa proceeded relatively rapidly, although the dredged site had clearly not fully recovered some 7 months later. Differences in the recruitment success of the dominant taxa, notably Dendrodoa grossularia and Balanus crenatus, between the reference and treatment sites pre- and post-dredging were observed. Possible explanations for these differences in relation to the observed physical alterations to the sea bed are discussed.