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

Abstract

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 it mons were sampled within this central depression two on the western border and two to the east of the depression Another station W AS sampled in m non-exploited area to the north of the depression Four stations were sampled outside of the concession area on the adjacent Middelkerke B ink 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 witness could not be detected between the different locations Compared to the reference stations it the Middelkerke Bank and locations next to the depression crustaceans (amphipods and in particular Bathyporeia spp) and echinoderms (Ophiura spp and Lchinocardium 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 ends 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 eat het for the Kwinte Bank together with other Belgian subtidal sandbanks Sand extraction h is created small scale habit it differences 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.