Methanogenesis in Arctic Permafrost Habitats

Abstract

SummaryIn polar regions, huge layers of frozen ground, termed permafrost, are formed. Permafrost covers more than 25 % of the land surface and significant parts of the coastal sea shelves. Permafrost habitats are controlled by extreme climate and terrain conditions. Particularly, the seasonal freezing and thawing in the upper active layer of permafrost leads to distinct gradients in temperature and geochemistry. Methanogenic archaea in permafrost environments have to survive extremely cold temperatures, freeze-thaw cycles, desiccation and starvation under long-lasting background radiation over geological time scales. Although the biology of permafrost microorganisms remains relatively unexplored, recent findings show that methanogenic communities in this extreme environment are composed by members of the major phyla of the methanogenic archaea (Methanobrevibacter, Methanobacterium, Methanosaeta, Methanosarcina, Methanolobus/Methanohalophylus/Methanococcoides, Methanculleus/Methanogenium), with a total biomass comparable to temperate soil ecosystems. Currently, methanogenic archaea were the object of particular attention in permafrost studies, because of their key role in the Arctic methane cycle and consequently of their significance for the global methane budget.2