AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00458

ABSTRACT: The Wadden Sea is a highly dynamic tidal system and an important area for a variety of species, including wild and cultivated mussels. Increased suspended sediment concentrations may negatively affect ecosystem functioning across trophic levels, hence insight in the effects of anthropogenic activities is of importance. The aim of this study was to investigate the scale of sediment resuspension associated with commercial mussel cultivation activities. Turbidity prior and during fisheries and harvest was investigated by in situ measurements with towed and fixed sensors. Four case studies were selected to represent maximum disturbance. For one case study, sediment resuspension was further investigated by analysis of satellite images. The in situ measurements showed that turbidity is enhanced by mussel fisheries and harvest, but that effects are limited in time and space. Turbidity enhancement during fisheries was several-fold higher than during harvest, whereas the spatial scale of both activities was limited to their direct vicinity. In contrast to the in situ study, the satellite image analysis identified a spatial magnitude that extended over a somewhat larger spatial scale and further revealed that this ‘dark water’ plume consisted of higher coloured dissolved organic matter (CDOM) concentrations rather than suspended particles. Along with turbidity, CDOM seems thus an important consideration for determining light attenuation in a water body affected by anthropogenic seafloor disturbance. As we presented case studies that were expected to represent maximum impact, we conclude that there is no specific need for further in-depth studies that allow upscaling to ecosystem-wide effects.