Sediment reworking mechanisms in shelf seas : In situ observations from the southeastern North Sea

The seafloor in shallow coastal and shelf seas is a highly dynamic system providing plenty of natural resources and important ecosystem services. Driven by energetic physical forcing, biological activity and intense anthropogenic use, its mobile sediments are constantly overturned. The reworking processes mediate the exchange of abundant organic matter and pollutants across the benthic interface. Coherent in situ measurements of forcing and morphodynamic response help to identify relevant reworking mechanisms, to outline their spatial and temporal scales, and to quantify their impacts on the benthic ecosystem. New high-resolution observation techniques enable also the assessment of small-scale processes that, due to their ubiquity, are yet of shelf-wide importance. This thesis explores three mechanisms in the southeastern North Sea: The morphology and dynamics of small scale-bedforms, the relation of physical and biogenic sediment reworking by bedform migration and bioturbation, and the effect of submarine fluid expulsion. The analysis of these processes reveals new links between physical and biological drivers and illustrates their complex interactions at the benthic interface.