Methane production in thawing permafrost is constrained by methanogenic population size and carbon density

The total methanogenic population size in turn varied by five orders of magnitude thus being highly heterogeneous and appeared to be a function of carbon density. In excess of methanogenic substrate carbon density further served as a good predictor for the potential production of CH4 after thaw. Finally, we propose that the millennial exposure to permafrost conditions bred high affinity methanogenic communities since we observed their inability to exhaust large concentrations of substrates and to substantially increase in population size after almost one year of incubation at moderate temperatures of 15°C in most of the incubations.

Our study further supports related work that on the long-term methane production can contribute substantially to the permafrost carbon feedback since random incubations showed a pronounced evolution of methane and increase in methanogenic population size, respectively.