Metabolic alkalinity release from large port facilities (Hamburg, Germany) and impact on coastal carbon storage

Abstract

Abstract. Metabolic activities in estuaries, especially these of large rivers, exert profound impact on downstream coastal biogeochemistry. Here, we unravel the contribution of large industrial port facilities to these impacts and show that metabolic activity in the Hamburg port (Germany) increases total alkalinity (TA) and dissolved inorganic carbon (DIC) runoff to the North Sea. We explained this activity to be fueled by the imports of particulate inorganic and organic carbon (PIC, POC) and particulate organic nitrogen (PON) from the upstream Elbe River, resulting in maximum 90 % TA generation due to CaCO3 dissolution in the entire estuary. The remaining 10 % can be attributed to a TA generation by anaerobic metabolic processes such as denitrification of remineralized PON, or other pathways. The Elbe Estuary as a whole adds approximately 15 % to the overall DIC and TA runoff. Both the magnitude and partitioning among these processes appear to be sensitive to climate and anthropogenic changes, and affects coastal CO2 storage capacity.