Regulation of oxygen dynamics by transport processes and microbial respiration in sandy sediments

More than 50% of the continental shelves are covered by sandy sediments that are permeable and allow for advective porewater flow. The interaction of small scale bedforms and bottom water currents creates pressure gradients, which pump reactive solutes and particles from bottom waters into the sediment where they stimulate benthic microbial communities. This accelerates benthic mineralization and nutrient turnover. So far, studies have generally assumed that the sediment is immobile, even though continental shelves are a high energy environment. Strong tidal currents and waves regularly mobilize the sea floor leading to changes in its morphology. Little is known about the regulation of solute and particle fluxes within sandy sediments when they are exposed to such variable morpho- and hydrodynamics. This thesis aims to improve our understanding of transport processes in sandy sediments and to identify physical and biological parameters controlling benthic biogeochemical cycling