Macrobenthos characteristics and distribution, following intensive sand extraction from a subtidal sandbank

Macrobenthic fauna are investigated, to establish the nature and vulnerability of benthic communities to aggregate mining on a subtidal sandbank, the Kwinte Bank, in the Southern Bight of the North Sea. Within the central part of this sandbank, a depression (5 m deep) has been created, as a result of 20 years of dredging over the same small area (1 km long and 700 m wide). Three stations were sampled within this central depression; two on the western border; and two to the east of the depression. Another station was sampled in a “non-exploited” area to the north of the depression. Four stations were sampled outside of the concession area, on the adjacent Middelkerke Bank. The hypothesis is tested as to whether or not the density, species richness, taxon and community composition do not differ, between the depression and the adjacent sites (with similar sediment composition) on top of the sandbank. In addition, it is examined whether these parameters differ between the depression and reference sites, at the adjacent undisturbed sandbank. Differences in density and species richness could not be detected, between the different locations. Compared to the reference stations at the Middelkerke Bank and locations next to the depression, crustaceans (amphipods and in particular Bathyporeia spp.) and echinoderms (Ophiura spp. and Echinocardium cordatum) were more abundant in the area of the depression, suggesting a higher similarity to the swale environment, than was the case previously. The observed trends were similar, for both of the sampling periods, February and November 2004. However, the species composition difference has been observed within the context of the wide range of species assemblages described earlier for the Kwinte Bank, together with other Belgian subtidal sandbanks. Sand extraction has created small-scale habitat differences on the Kwinte Bank, to which the benthic fauna have adjusted; however, this is not significant on a true larger scale of the sandbank system, one year after cessation of the intensive disturbance