Background The Arctic plays a key role in the Earths climate system, because global warming is predicted to be most pronounced at high latitudes, and one third of the global carbon pool is stored in ecosystems of the northern latitudes. The degradation of permafrost and the associated release of climate-relevant trace gases from intensified microbial turnover of organic carbon and from destabilized gas hydrates represent a potential environmental hazard.Microbial processes and methane fluxesThe mean flux rate from polygon depressions was 53.2 ± 8.7 mg CH4 m-2 d-1, whereas the mean flux rate of the dryer rim part of the polygon was 4.7 ± 2.5 CH4 m-2 d-1. The CH4 production in the upper soil horizon of the polygon depression was about 10 times higher (38.9 ± 2.9 nmol CH4 m-2 d-1) in July than in August (4.7 ± 1.3 nmol CH4 m-2 d-1). The CH4 oxidation behaved exactly in reverse: the oxidation rate of the upper soil horizon was low in July (1.9 ± 0.3 nmol CH4 m-2 d-1) compared to the activity in August (max. 7.0 ± 1.3 nmol CH4 m-2 d-1). The findings demonstrate the close relationship between apparent methane fluxes and the modes and intensities of microbiological processes of methane production and oxidation in the polygonal tundra soils.Research needs Despite increasing studies on microbial processes and communities in permafrost envirnments [1, and ref. within there], their function, population structure and reaction to environmental changes is largely unknown, which means that also an important part of the process knowledge on methane fluxes in permafrost ecosystems is far from completely understanding. This hampers prediction of the effects of climate warming on arctic methane fluxes, in particular when these predictions are based on models that do not take into account the specific nature of microbial populations in permafrost soils and sediments. Understanding these microbial populations is therefore highly important for understanding the global climatic effects of a warming Arctic.[1] Wagner & Liebner (2009) Soil Biology 16, 219-236, Springer Berlin Heidelberg