BioGeoChemistry of Tidal Flats


M. Grunwald, O. Dellwig, J. Freund, A. Lübben, R. Reuter, H. J. Brumsack

Tidal variations of dissolved methane in the wadden sea of NW Germany

Methane is a reactive trace gas which contributes in a large scale to the world’s climate and the carbon budget. The tidal flat system of the study area is connected to freshwater courses and the North Sea. Methane measurements were carried out in the freshwater environment, the Wadden Sea water column, and the open North Sea, with distinctly decreasing concentrations towards the North Sea. One goal of our investigations is to budget the methane fluxes into and out of the Wadden Sea system. Dissolved methane in the water column is continuously measured with a methane sensor at a time-series station near Spiekeroog Island where hydrological and meteorological parameters are determined as well. Methane sources are the freshwater and the tidal flat sediments, assuming the latter to be of more importance. Continuous measurements show a tidal cyclicity with two-times higher concentrations at low tide, which points towards a net export to the North Sea. Despite of biological processes and hydrology, methane concentrations seem to be influenced by meteorology. Thus, time-series analyses show a time-shifted dependence of methane concentrations on the wind current.