Distribution and source attribution of alkalinity in the Dutch Wadden Sea

Abstract. As the major global CO₂ sink, the oceanic buffering capacity total alkalinity (TA) is of growing scientific interest. TA is mainly generated by weathering, and further by various anaerobic metabolic processes. The Wadden Sea, located in the southern North Sea is thought to be a source of TA for the carbonate system of the North Sea, but quantifications are scarce. Here, we observed TA, dissolved inorganic carbon (DIC), and nutrients in the Dutch Wadden Sea in May 2019. We sampled transect surface waters to detect spatial distributions and compared it with earlier data. A tidal cycle was sampled to further shed light on TA generation and potential TA sources. We identified the Wadden Sea as a source of TA with an average TA generation of 7.6 µmol kg^-1 h^-1 during ebb tide in the Ameland Inlet. TA was generated in the sediments and washed out with off running water. A combination of anaerobic processes and CaCO₃ dissolution were potential sources of TA in the sediments. We assume that seasonality and the associated nitrate availability in particular influence TA generation by denitrification, which we assume is low in spring and summer.