BioGeoChemistry of Tidal Flats


Y. C. Hilker, A. Gittel, H. Cypionka, B. Engelen

Vertical distribution of bacterial communities involved in the methane cycle of tidal flat sediments

Methane concentrations in the East Frisian Wadden Sea near the island of Spiekeroog were found to be hundred times higher than in the open ocean. To clarify sources and sinks of this climatically active gas in tidal flats, a 5-m-long sediment core was investigated. The core was characterized geochemically including methane- and sulfate-concentration measurements. Rates of anaerobic oxidation of methane (AOM) were determined by means of radio tracers. The abundance of sulfate reducers and methanogenes was determined by quantitative PCR using specific primers for the dsrAB- and mcrA-gene. The profiles of methane and sulfate were mirrored in the profiles for the dsrAB- and mcrA-genes. The correlation of molecular signatures and total cell counts will be taken to identify the zone of anaerobic methane oxidation. The sulfate-methane transition zone between 350 to 400 cm sediment depth is supposed to be a hot spot of anaerobic methane oxidation indicating that AOM take place at lower pressure. In future investigations, methane oxidation in the oxic compartments of the Wadden Sea will be determined to calculate the methane flux within the system.