Due to elevated emissions of carbon dioxide (CO₂) into the atmosphere, oceanic uptake of CO₂ is increasing and the oceanic carbonate system altered in a phenomenon termed Ocean Acidification (OA). How come that in relatively shallow shelf systems like the North Sea, the trend in pH decrease of the open ocean is not followed ? Which geochemical processes contribute to this discrepancy? To answer these questions, the Master student will collect sediments from the Oosterschelde for measuring fluxes of alkalinity, DIC, O₂, dissolved metals and nutrients between the sediment and the overlying water in the presence and absence of larger biota and modelled as a function of biological activity.