G. Moerkerke

Fine-scale geomorphological mapping of sandbank environments for the prediction of macrobenthic occurrences, Belgian Part of the North Sea

Publisher Summary Fine-scale geomorphological mapping is demonstrated to be able to predict macrobenthos occurrences within shallow sandbank areas of the Belgian part of the North Sea. The Belgian part of the North Sea (BPNS) is a siliciclastic macrotidal environment comprising several groups of sandbanks. The sandbanks represent a thin and patchy Holocene cover, which overlies Tertiary clayey sediments that outcrop locally in troughs. Sediment transport is mainly driven by tidal currents, though wind-induced currents and waves may have a direct effect on sediment resuspension and bedform morphology. Human activities are widespread and relate mainly to harbor infrastructure works, dredging and disposal of dredged material, marine aggregate extraction, and windmill farm construction. The statistical habitat suitability model predicts the occurrence of the four macrobenthic communities based only on median grain size and silt–clay content. On the scale of the BPNS, marine landscapes have been mapped and translated into macrobenthic community preferences. The emphasis is placed upon relationships between the macrobenthos and the fine-scale geomorphological and sediment nature, for which sonar imagery is needed. Ideally, seafloor classification techniques would allow automated discrimination of acoustic facies, but results did not depict the fine-scale variation, as seen from the imagery. Interpretation in terms of bedforms and sedimentary characteristics led to 15 acoustic facies, which were further related to macrobenthic community occurrences. Successful validation over the entire Belgian coastal zone promotes its use for classifying sandbank environments. Furthermore, it is demonstrates that sidescan sonar and multibeam technology can be used to directly map reefs of tube-building polychaetes. These ecosystem engineers are key species within hotspots of biodiversity among inter- and subtidal soft sediment environments of the North Sea.