Two-million-year-old microbial communities from the Kap København Formation in North Greenland

Abstract

Using ancient environmental DNA (eDNA)1 we reconstructed microbial and viral communities from the Kap København Formation in North Greenland2. We find pioneer microbial communities, along with likely dormant methanogens from the permafrost's seed bank. Our findings reveal that at the time of the formation, the terrestrial input of the Kap København site originated from a palustrine wetland, suggesting non-permafrost conditions. During this time, detection of methanogenic archaea and carbon processing pathways suggests a moderate strengthening of methane emissions through the northward expansion of wetlands. Intriguingly, we discover a remarkable sequence similarity (>98%) between pioneer methanogens and present-day thawing permafrost counterparts. This suggests that not all microbes respond uniformly to environmental change over geological timescales, but that some microbial taxa’s adaptability and resilience remain constant over time. Our findings further suggest that the composition of microbial communities is changing prior to plant communities as a result of global warming. 3 bioRxiv preprint doi: https://doi.org/10.1101/2023.06.10.544454; this version posted June 12, 2023. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license. Main In recent years, ancient environmental DNA (eDNA)1 has transformed our understanding of ecosystem dynamics and how ecosystems have evolved in response to environmental changes3– 5 . Using eDNA preserved in the Kap København Formation, Kjær et al.2 reconstructed the plant and animal communities that inhabited North Greenland ~2 million years ago (Fig. 1A), and found a complex and diverse species assemblage that has no modern analogue. However, this study do not consider the microbes which play fundamental roles in the maintenance of biogeochemical processes that shape the community structure of multicellular organisms6–8. The characterisation of the microbial eDNA component is crucial for insights into the complex functioning of past ecosystems. In fact, most sedimentary ancient DNA studies typically neglect microbial communities8, primarily due to their dynamic nature, which distinguishes them from plant and animal communities whose genetic signals are not overprinted by continued activity within the deposit. …