Methanogenic response to long-term permafrost thaw is determined by the paleoenvironment

We investigated the response of the methanogenic archaeal community in Siberian permafrost to long term thaw (2-7 years) using interglacial permafrost from Holocene and Eemian deposits, and glacial permafrost of both stadial and interstadial origin from the Pleistocene. Samples were obtained during drilling campaigns of two sites of Northeast Siberia, Kurungnakh Island (72°.20.N, 126°17.E) and the second on Bol'shoy Lyakhovsky Island (73°20. N, 141°30.E). We applied a 16S rRNA amplicon based approach applying archaeal specific primers. Methane and carbon dioxide production were continuously measured throughout the incubation. Enumeration of methanogenic mcrA gene copies, indicative for the methanogenic population size, was performed by quantitative PCR (qPCR) on the initial samples and by the end of the long-term incubations.