Microbial Carbon Cycling in Permafrost-Affected Soils

The Arctic plays a key role in Earth s climate system as global warming is predicted to be most pronounced at high latitudes and because one third of the global carbon pool is stored in ecosystems of the northern latitudes. In order to improve our understanding of the present and future carbon dynamics in climate sensitive permafrostecosystems, present studies concentrate on investigations of microbial controls of greenhouse gas fluxes, on the activity and structure of the involved microbial communities, and on their response to changing environmental conditions. Permafrost-affected soils can function as both a source and a sink for carbon dioxide and methane. Under anaerobic conditions, caused by flooding of the active layer and the effect of backwater above the permafrosttable, the mineralization of organic matter can only be realized stepwise by specialized microorganisms. Important intermediates of the organic matter decomposition are hydrogen, carbon dioxide and acetate, which can be further reduced to methaneby methanogenic archaea. Evolution of methanefluxes across the subsurface/atmosphere boundary will thereby strongly depend on the activity of anaerobic methanogenic archaeaand obligately aerobic methaneoxidizing proteobacteria, which are known to be abundant and to significantly reduce methane emissionsin permafrost-affected soils. Thereforemore » current studies on methane-cycling microorganisms are the object of particular attention in permafroststudies, because of their key role in the Arctic methanecycle and consequently of their significance for the global methanebudget.« less