Is the Wadden Sea a source of greenhouse gases, and what role do mudflats, sediments, groundwater and inflows from land play in this? A consortium of six research institutions is investigating these questions in Meldorf Bay. Using two research vessels, and a measuring pontoon, the teams are recording the exchange of gases between land, water and the atmosphere. There is a particular focus on methane, as previous measurements have shown elevated concentrations of the gas in the mudflats.
Anyone looking out across the Wadden Sea at low tide probably doesn’t think of greenhouse gases as the first thing that springs to mind. Yet processes are constantly taking place in the sediment and in the water, during which carbon is converted and greenhouse gases are produced, absorbed or transported further. The extent of these material flows and which sources are significant has been little researched, particularly in coastal areas.
As part of a joint measurement campaign, scientists from six German research institutions are now investigating greenhouse gases in a measurement section established around Meldorf Bay. “The coast is the interface between land and ocean: here, carbon compounds are transformed, transported and released again with the tides within a short space of time,” says Dr Ingeborg Bussmann, a biogeochemist at the Alfred Wegener Institute (AWI) on Heligoland, who is coordinating the campaign. “We are particularly interested in where methane is produced and how much of it actually enters the atmosphere.”
Previous measurements have repeatedly revealed elevated concentrations of dissolved methane near mudflat areas. However, it is still unclear where the gas originates. One possible source lies in the mudflat sediment. There, microorganisms break down organic material and may produce methane in the process. However, the gas could also enter the bay via groundwater from the sediments. Another possibility is inflows from the mainland, which enter the coastal waters via sluices. The measurements are intended to help distinguish between these different pathways.
The Wadden Sea campaign is a component of the ElbeXtreme project (a collaborative project within the research mission of the German Alliance for Marine Research, DAM), which addresses the impacts of extreme events in the Elbe estuary and the German Bight. The data from the campaign will be incorporated into the numerical modelling and the planned information and decision-support system of ElbeXtreme, thereby supporting risk understanding and resilience planning for coastal ecosystems and local communities. “With the Wadden Sea campaign, we are filling a key knowledge gap: to what extent do mudflats that fall dry contribute to CO2, methane and nitrous oxide fluxes in extreme years such as 2026? By simultaneously sampling water, sediment and the atmosphere, we are creating the data foundation for realistic models and sound decisions on the protection and management of our coastal regions,” says Prof. Dr Eric Achterberg, professor in the Marine Biogeochemistry Research Division at GEOMAR Helmholtz Centre for Ocean Research Kiel and consortium leader of ElbeXtreme.
Further information on the Wadden Sea campaign can be found in the GEOMAR press release.
