Investigating the role of soil microbial processes in aquatic greenhouse gas emissions in Eastern Canadian permafrost landscapes

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Greenhouse gas (GHG) emissions from thawing permafrost represent a major potential positive feedback to global warming, but our understanding of the biological, geochemical, and hydrological mechanisms controlling these emissions remains limited. Recent research points to aquatic environments (lakes and ponds) as hotspots of GHG emissions, but the pathways through which permafrost soil carbon contributes to aquatic GHG emissions remain unclear. Currently there is a lack of research integrating microbiological, biogeochemical, and hydrological processes in soils and aquatic environments in permafrost landscapes, which this interdisciplinary project aims to address. We will study these processes in ecosystems in Eastern Canada representing both continuous and discontinuous permafrost. Our FRQNT-funded research project focuses on (1) characterizing relationships between microbial communities, organic matter (OM), and GHG fluxes across soil to aquatic environmental gradients through field sampling and (2) identifying the mechanisms controlling linkages between microbial communities and GHG fluxes using incubation experiments. Our team comprises strong expertise in carbon cycle biogeochemistry (Peter Douglas- McGill), Arctic aquatic ecology (Isabelle Laurion-INRS), soil microbiology (Cynthia Kallenbach- McGill), microbial genomics (Jérôme Comte- INRS), and nutrient biogeochemistry (Roxane Maranger- Université de Montréal). New funding from the NSERC NOVA program will facilitate collaboration with a hydrologist (Melissa Lafrenière-Queens), broadening the research program to focus on specific mechanisms of hydrological transport of organic matter, microbes, and nutrients from soils to ponds. This will include examination of the role of summer rainfall and different size classes of organic matter in controlling soil-pond carbon fluxes. It will also facilitate a comparative analysis of rapidly eroding gullies with permafrost thaw ponds in terms of their potential for mobilizing permafrost carbon reservoirs. This new funding study will provide key insights into mechanistic linkages between soil microbiology, hydrology, and permafrost GHG emissions.