Microbial community composition and abundance after millennia of submarine permafrost warming

Abstract

Abstract. Warming of the Arctic led to an increase in permafrost temperatures by about 0.3 ∘C during the last decade. Permafrost warming is associated with increasing sediment water content, permeability, and diffusivity and could in the long term alter microbial community composition and abundance even before permafrost thaws. We studied the long-term effect (up to 2500 years) of submarine permafrost warming on microbial communities along an onshore–offshore transect on the Siberian Arctic Shelf displaying a natural temperature gradient of more than 10 ∘C. We analysed the in situ development of bacterial abundance and community composition through total cell counts (TCCs), quantitative PCR of bacterial gene abundance, and amplicon sequencing and correlated the microbial community data with temperature, pore water chemistry, and sediment physicochemical parameters. On timescales of centuries, permafrost warming coincided with an overall decreasing microbial abundance, whereas millennia after warming microbial abundance was similar to cold onshore permafrost. In addition, the dissolved organic carbon content of all cores was lowest in submarine permafrost after millennial-scale warming. Based on correlation analysis, TCC, unlike bacterial gene abundance, showed a significant rank-based negative correlation with increasing temperature, while bacterial gene copy numbers showed a strong negative correlation with salinity. Bacterial community composition correlated only weakly with temperature but strongly with the pore water stable isotopes δ18O and δD, as well as with depth. The bacterial community showed substantial spatial variation and an overall dominance of Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadetes, and Proteobacteria, which are amongst the microbial taxa that were also found to be active in other frozen permafrost environments. We suggest that, millennia after permafrost warming by over 10 ∘C, microbial community composition and abundance show some indications for proliferation but mainly reflect the sedimentation history and paleoenvironment and not a direct effect through warming.

Evidence for signatures of ancient microbial life in paleosols

“…Possibly, changes in MCC occurring after burial have blurred these signatures. It thus appears that the preservation of paleoenvironmental signatures in the MCC of this loess-paleosol sequence is weaker compared to findings from some permafrost, aquatic or subseafloor sediments [34][35][36] .…”

Greenhouse gas production and lipid biomarker distribution in Yedoma and Alas thermokarst lake sediments in Eastern Siberia

“…Figure 3), yet comparable to pore water from Yedoma deposits on Buor Khaya, northeastern Siberia (median: 317 mg L −1 , max: 1371 mg L −1 ; Schirrmeister et al, 2017). In addition, Ewing et al (2015) (Mitzscherling et al, 2019), or for Samoylov Island, ranging from 57 to 288 mg L −1 (Liebner et al, 2008).…”

“…In addition, Ewing et al (2015) reported high maximum DOC values in Alaskan Yedoma pore water (median: 618 mg L −1 , max: 1551 mg L −1 ). For comparison, other studies from northeastern Siberia reported much lower pore water DOC values such as for early to middle Weichselian sediments on the Cape Mamontov Klyk, ranging from 4 to 305 mg L −1 (Mitzscherling et al, 2019), or for Samoylov Island, ranging from 57 to 288 mg L −1 (Liebner et al, 2008).…”

Archaeal Communities of Frozen Quaternary Sediments of Marine Origin on the Coast of Western Spitsbergen

“…Сообщества, характеризуемые присутствием архейных филумов Euryarchaeota, Bathyarchaeota, Thaumarchaeota, Asgardarchaeota, по преобладающим филумам оказались схожими с сообществами современных прибрежных [Mitzscherling et al, 2019] и морских отложений, связанных с метаногидратными пинго [Gründer et al, 2019;Treude et al, 2020]. Как и представители домена Bacteria (см.…”

“…Доминирующими группами домена Archaea в вечной мерзлоте в районе м. Мамонтов Клык (западная часть моря Лаптевых) возрастом около 2500 лет являются анаэробные метаногенные аммонийокисляющие и метанокисляющие археи [Mitzscherling et al, 2019]. В вечной мерзлоте бух.…”