Understanding the Role of Permafrost-Affected Microbes in Thawing Arctic
Authors:
Fumnanya Abuah1* ([email protected]), Tatiana A. Vishnivetskaya1, Katie Sipes1,9, Joy Buongiorno1, James Bradley3, Donato Giovannelli4, Andrey Abramov5, Samantha Peters6, Richard J. Giannone6, Robert L. Hettich6, Julia Boike7, Sarahi L. Garcia8, Andrew D. Steen1,2, Karen G. Lloyd1
Institutions:
1Microbiology Department, University of Tennessee–Knoxville; 2Department of Earth and Planetary Sciences, University of Tennessee–Knoxville; 3Queen Mary College; 4University of Naples Federico II; 5Institute of Physicochemical and Biological Problems of Soil Science; 6Biosciences Division, Oak Ridge National Laboratory; 7Alfred Wegener Institute; 8Department of Ecology, Environment, and Plant Sciences, Science for Life Laboratory, Stockholm University; 9Department of Environmental Sciences, Aarhus University
Goals
Using integrative metaomics technologies, determine a role of natural microbial populations in pristine permafrost, seasonally thawed active layer, and hydrogeologically connected fjord sediments to degradation of organic matter and contribution to climate feedbacks in thawing Arctic.
Abstract
Permafrost and permafrost-affected areas cover approximately 24% of the global terrestrial surface and reserve ~50% of the total soil organic carbon. Global warming drives permafrost degradation, release of organic carbon to decomposition, and intensification of microbial activity that in its turn leads to the increase of greenhouse gases flux exacerbating climate-change feedbacks. Biodiversity of heterotrophic microbes and the metabolic pathways they use to convert newly available organic matter to carbon dioxide and methane are little studied. Increased availability of organic carbon from thawing permafrost threatens to create a positive feedback on climate change, and since thawing organic carbon is transported by subterranean groundwater flow into nearby rivers or fjords, these microbial feedbacks involve communities in thawing permafrost as well as those in hydrogeologically connected soils. Greenhouse gas emissions at the soil surface are an amalgamation of microbial activity in all the layers underneath, so knowing the vertical layering of microbial communities is key to understanding the mechanisms of these climate change feedbacks.
Svalbard, Norway (79°N) is experiencing faster warming than the rest of the high Arctic, making it a bellwether for Arctic permafrost. The samples of permafrost and active layer were collected during winter at the Bayelva field site, and fjord sediments were collected during spring in close proximity to Ny Ålesund, Svalbard. The team examined in situ microbial communities using metagenomics, culturing, and extracellular enzyme assays from the surface down to 141 cm. Researchers compared the vertical layering of these communities and their carbon-degrading genes to those found in the adjacent marine fjord sediments using metagenomics, metatranscriptomics, and metaproteomics. Using comparative metagenomics and metagenome assembled genomes (MAGs), the team showed the depth distribution of individual MAGs leads to layered activity. The higher abundance of genes and peptides for major carbohydrate active enzymes (CAZymes) and glycoside hydrolases in subsurface at depths around 30 cm and 80 to 90 cm suggests that subsurface microbial communities are more active due to insulation from harsh surface conditions and due to high liquid water content, even though the deeper soils are sustained by older deposits of organic matter. Importance of the phyla of Verrucomicrobia and Proteobacteria was shown in both fjord sediments and permafrost-affected soils. Even though some matches between organisms that are capable of degrading similar organic matter in soils and the fjords were shown, the activity profiles differed from taxonomic profiles based on genetic potential alone. Researchers found significant overlap in potential for organic matter degradation in the subsurface of both the permafrost active layer and the fjord. It is likely that these subsurface communities are supported by the higher liquid water contents in the soil subsurface as well as depth-related changes in terminal electron accepting processes in fjord sediments. This suggests a direct role of subsurface microbial communities in a potential feedback loop with climate change, where thawing permafrost releases organic matter to active microbes which, in turn, convert the organic matter to greenhouse gases that may further warm the climate.
References
Abuah, F., et al. “Investigating Microbial Communities in Svalbard Permafrost,” AGU Fall Meeting. Chicago, IL. 12–16 December 2022. B12I-1154.
Abuah, F., et al. “Subsurface Microbes May Drive Climate Feedbacks in Thawing Arctic Permafrost,” Geobiology GRC. Galveston, TX. 14–19 January 2024, #33.
Funding Information
This study was supported by the U.S. DOE, Office of Science, BER program, GSP (DE-SC0020369).