09 Nov 2023
 | 09 Nov 2023
Status: this preprint is open for discussion.

Distribution and source attribution of alkalinity in the Dutch Wadden Sea

Mona Norbisrath, Justus E. E. van Beusekom, and Helmuth Thomas

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.

Mona Norbisrath et al.

Status: open (until 05 Jan 2024)

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Mona Norbisrath et al.

Mona Norbisrath et al.


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Short summary
Observational study that investigated total alkalinity (TA) in the Dutch Wadden Sea. We collected discrete water samples to identify spatial TA distribution patterns and to locate and shed light on potential TA sources. By observing a tidal cycle in the Ameland Inlet, we identified the sediments as a local TA source and assumed aerobic metabolic processes eg CaCO3 dissolution as a TA source in the upper oxic sediments, and anaerobic metabolic processes as a TA source in the deeper anoxic ones.