Symbiotic relationships couple nitrogen and carbon cycles for the production of greenhouse gases in thermokarst ponds

With the rapid warming of the Arctic, permafrost-affected landscapes are undergoing transitions, including the formation of thermokarst ponds. However, the mechanisms driving greenhouse gases (GHG) cycles in these systems remain relatively unexplored. Previous research showed that thermokarst microbial communities are strongly shaped by nitrogen species and by the quality of dissolved organic matter (DOM). Here, we hypothesized that potential symbiotic or consortium relationships influence GHG production by coupling carbon (C) and nitrogen (N) cycles. As these associations can be influenced by the state of permafrost degradation, we investigated the key functions and pathways of N and GHGs cycles in two permafrost degradation state, a sporadic subarctic permafrost (Whapmagoostui-Kuujjuarapik, Québec) and a continuous Arctic permafrost site showing early signs of degradation (Bylot Island, Nunavut). We used hybrid next-generation sequencing combining short-read paired-end Illumina and long-read Oxford Nanopore for pathways and metagenome-assembled genomes (MAGs) reconstruction. First results revealed various pathways potentially fueling methanogenesis in subarctic thermokarst ponds, notably the involvement of symbiotic relationships between acetate producers and archaeal methanogens, and their link to the quality of the DOM. Ongoing metagenomic analyses of the continuous permafrost site will elucidate whether similar patterns are in place. This research sheds light on the complex interplay between microbial communities, GHG dynamics, C and N cycles in thermokarsts ponds.

Primary Presenter: Martial Leroy, Institut national de la recherche scientifique (martial.leroy@inrs.ca)

Authors:

Martial Leroy, Institut national de la recherche scientifique  (martial.leroy@inrs.ca)

Valentine Cyriaque, Institut national de la recherche scientifique  (valentine.cyriaque@inrs.ca)

Isabelle Laurion, Institut national de la recherche scientifique  (isabelle.laurion@inrs.ca)

Thomas Rattei, Centre for Microbiology and Environmental Systems Science, Life Science Compute Cluster, University of Vienna  (thomas.rattei@univie.ac.at)

Jérôme Comte, Institut national de la recherche scientifique  (jerome.comte@inrs.ca)