Benthic sources for dissolved inorganic carbon in the North Sea: A stable isotope perspective

Marine sediments may act as a sink for carbon. Substrate and electron donor availabilities, sedimentology, as well as biological activity may influence the carbon cycling, impacting the release of TA and DIC. The North Sea is a highly dynamic system with shallow tidal areas and fresh water tributaries delivering nutrients and dissolved carbon. For the southern part, benthic DIC sources have been identified [1], with tidal areas being further hot spots [2], some being impacted by submarine fresh water discharge [3]. The Skagerrak provides the unique opportunity of studying benthic DIC production under the impact of different dominant electron acceptors [4]. Potential transformation of carbonates may impact release of TA and DIC.

Here, we investigated the role of different sediments from the North Sea, including tidal areas, for their DIC source function and carbon storage capacity. Water column, pore water, and sediment samples were investigated to understand the processes controlling the benthic production and release of TA and DIC. The carbon isotope composition of dissolved and solid phases were investigated to understand the specific biogeochemical processes dominating benthic mineralization and carbonate dissolution.

[1] Burt et al. (2016) Limnol. Oceanogr. 61, 666-683. [2] Schwichtenberg et al. (2020) Biogeosciences, 17, 4223-4245. [3] Winde V. et al. (2014) J. Mar. Sys. 129, 394-402. [4] Canfield D.E. et al. (1993) Geochim Cosmochim Acta 57, 3867-2883.

The investigations are carried out within the BMBF project COOLSTYLE/CARBOSTORE. The Sylt part also contributes to the DFG project KiSNet, and investigations are further supported by Leibniz IOW.