Seasonal changes in total alkalinity and dissolved inorganic carbon in the southern North Sea and intertidal regions around the North Frisian Islands

Coastal regions are highly variable ecosystems and play a crucial role in the global carbon cycle. In the North Sea, the CARBOSTORE project aims to investigate some of the benthic and pelagic reservoirs of carbon. This study focuses on the seasonal and inter-annual changes in the Southern North Sea and the North Frisian Islands in the Wadden Sea. Large regional and seasonal variability has been documented in previous studies of total alkalinity and carbon in these regions, but the driving factors are still being investigated.

Since the start of the CARBOSTORE project in spring 2021, two seasonal cruises were completed in July and October 2021. The dissolved inorganic carbon (DIC) and total alkalinity (TA) in the southern North Sea and intertidal regions around the North Frisian Islands were measured, along with several other biogeochemical parameters measured using a Ferry Box. These surveys allow insights into the regional distribution and the seasonal cycle of TA and DIC and will help elucidate the potential sources of carbon. In addition, a close collaboration to colleagues investigating the benthic processes in this project will allow for coupling the benthic and pelagic dynamics.

Preliminary results show a gradient in TA and DIC from land to sea, as well as regional variability. In the intertidal zones, TA and DIC values are higher overall than in the southern North Sea. Higher TA and DIC values were measured in July compared to October. What is more, the intertidal regions near the Ems River show some of the highest TA and DIC values, suggesting a potential influence from riverine inputs.