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Abstract

Gas hydrates are ice-like crystalline solids composed of a three-dimensional network of hydrogen-bonded water molecules that confines gas molecules in welldefined cavities of different sizes. Since gas hydrates form under elevated pressure conditions at low temperatures they often occur in permafrost regions when sufficient amounts of water and gas are present. In this natural setting the gas is predominantly methane of microbial or thermogenic origin. In different field studies the occurrence of microbial methane in and below the permafrost could be proved: Collett and Dallimore (1998) report on intra-permafrost microbial methane in drill cores from the 92GSCTAGLU, the 92GSCKUMAK and the 92GSCUNIPKAT wells, situated close to a potential future scientific drilling target (NWT, Canada). The occurrence of intrapermafrost microbial methane has also been observed during drilling of the Mallik 4L-38 and 5L-38 wells (NWT, Canada). In submarine permafrost microbial methane occurrences could be detected in cores from the Siberian Arctic Shelf (Koch et al. 2009). Noteworthy, the noble gas abundance data from Mallik imply that the source of gases were gas hydrates. The relationship between gas hydrates, microorganisms and the surrounding sediment is extremely complex: Microorganisms producing methane provide the prerequisite for gas hydrate formation. However, as a result of microbial activity not only methane will be provided for hydrate formation but gas hydrates are surrounded by a great variety of organic compounds. These organic compounds are not incorporated into the hydrate structure but may influence the formation or degradation process. To understand the influence of microbial activity on the methane hydrate formation process and the stability conditions of the resulting hydrate phase we perform laboratory studies. Thereby, we mimic gas hydrate formation in the presence and absence of methanogenic archaea (e.g. Methanosarcina soligelidi) and other psychrophilic bacteria isolated from permafrost environments of the Arctic and Antarctic. Our results may contribute to understand and predict the occurrences and behavior of potential gas hydrates within or adjacent to the permafrost.