Wet tundra environments of the Siberian Arctic are natural sources of the climate relevant trace gas methane. The relevance of Arctic carbon reservoirs is highlighted by current climate models that predict significant changes in temperature and precipitation in the northern hemisphere. In order to improve our understanding of the present and future carbon dynamic in polar regions the methane content as well as the activity, diversity and physiology of the methanogenic community in permafrost sediments have to be studied. For these investigations permafrost cores of Holocene and late Pleistocene age were drilled in the Lena Delta, Siberia (N 72°, E 126°). The permafrost deposits are characterized by silty material with a high ice content between 11 and 35 %. The organic carbon of the core material varied between 0.6 and 4.9 %. In all permafrost deposits a high CH4 concentration were proven and methanogenesis could be initiated after thawing of the sediment. Even the incubation of soil material at 3 °C (0.1 11.4 nmol CH4 h-1 g-1) and 6 °C (0.08 4.3 nmol CH4 h-1 g-1) showed a significant CH4 production. Phospholipid etherlipid (PLEL) analysis revealed a high amount of archaeal biomass in permafrost layers with high concentrations of methane. Even up to 8.5 m permafrost depth archaeal PLEL were detected, although at low amounts.The results indicated the existence of a permafrost microbiota, which has well adapted to the extreme environmental conditions. Furthermore, first evidence of modern methanogenesis in the perennially frozen sediments was given by microbial activity and PLEL analysis. The characterization of pure cultures of methanogenic archaea obtained from permafrost environments should deliver detailed information of metabolic activity, survival potential and adaptation strategies of the microorganisms in extreme habitats.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL7-From permafrost to deep sea in the Arctic