Response of methanogenic archaea to Late Pleistocene and Holocene climate changes in the Siberian Arctic

Abstract

[1] In order to investigate the link between the methane dynamics in permafrost deposits and climate changes in the past, we studied the abundance, composition, and methane production of methanogenic communities in Late Pleistocene and Holocene sediments of the Siberian Arctic. We detected intervals of increased methane concentrations in Late Pleistocene and Holocene deposits along a 42 ka old permafrost sequence from Kurungnakh Island in the Lena Delta (northeast Siberia). Increased amounts of archaeal life markers (intact phospholipid ethers) and a high variety in genetic fingerprints detected by 16S ribosomal ribonucleic acid gene analyses of methanogenic archaea suggest presently living and presumably active methanogenic archaea in distinct layers predominantly in Holocene deposits, but also in deep frozen ground at 17 m depth. Potential methanogenic activity was confirmed by incubation experiments. By comparing methane concentrations, microbial incubation experiments, gene analysis of methanogens, and microbial life markers (intact phospholipid esters and ethers) to already partly degraded membrane lipids, such as archaeol and isoprenoid glycerol dialkyl glycerol tetraethers, we demonstrated that archaeol likely represents a signal of past methanogenic archaea. The archaeol signal was used to reconstruct the response of methanogenic communities to past temperature changes in the Siberian Arctic, and the data suggest higher methane emissions occurred during warm periods, particularly during an interval in the Late Pleistocene and during the Holocene. This new data on present and past methanogenic communities in the Siberian terrestrial permafrost imply that these microorganisms will respond to the predicted future temperature rise in the Arctic with increasing methane production, as demonstrated in previous warmer periods.

The development of permafrost bacterial communities under submarine conditions

“…In subseafloor sediments, the microbial abundance usually shows an exponential decrease with depth [ Kallmeyer et al, ]. In C2, however, maximum microbial abundances, bacterial gene copy numbers, and DNA concentrations occurred in the unaffected permafrost unit, which confirms that even in frozen sediments microbial cells can be conserved and survive within thin brine veins [ Steven et al, ; Wagner et al, ; Bischoff et al, ]. C2 also exhibited a quite constant diversity and richness in all pore water units except for PW IV.…”

Increasing Organic Carbon Biolability With Depth in Yedoma Permafrost: Ramifications for Future Climate Change

“…Prior studies have also found large abundances of Methanomicrobia in Alaskan soils (Malard & Pearce, ). Methanogens have also been detected in buried yedoma permafrost in northeast Russian (Bischoff et al, ; Rivkina et al, ) and the CRREL permafrost tunnel in Fox, AL (Mackelprang et al, ). In the CRREL permafrost tunnel, methanogen relative abundance decreased with increasing permafrost age (Mackelprang et al, ), while in our study at the VC permafrost tunnel methanogen relative abundance did not significantly change with depth.…”

Predicting long‐term carbon mineralization and trace gas production from thawing permafrost of Northeast Siberia

“…Since methanogenesis started with a very long lag phase and generally did not reach stable production rates until the end of the incubations, we could not model CH 4 production with the applied carbon degradation model. Low initial methane production rates (<0.01 μmol gdw −1 day −1 ) have been measured repeatedly in permafrost samples (Bischoff et al ., in press; Rivkina et al ., ; Wagner et al ., ). Even measurements for more than 1 year indicate the minor importance of methanogenesis in comparison to CO 2 production (Lee et al ., ).…”

“…The long time of more than one year needed to establish the highest methane production rates, supports the hypothesis of a relatively low abundance of methanogens in permafrost. However, a positive response of methanogenic communities to warmer and wetter periods in the Holocene and Late Pleistocene, as reconstructed from corresponding permafrost deposits of the Lena Delta, supports the assumption of increasing methane production and release when permafrost thaws (Bischoff et al ., in press).…”

“…Hence, permafrost thawing may provoke a positive feedback to climate warming by causing increased greenhouse gas emissions. Recently, a positive feedback of methanogenic communities to warmer periods in the Late Pleistocene and Holocene was shown for the Lena River Delta (Bischoff et al ., in press).…”