Terrestrial-aquatic connectivity structures microbial communities during the formation of thermokarst lakes.

Rising air temperatures and permafrost degradation drive the erosion of palsas (permafrost mounds mainly composed of frozen peat and ice layers) and lead to the formation of thermokarst ponds and lakes, known for their high greenhouse gas (GHG) emissions. This study investigates the impact of permafrost soil erosion during thermokarst lake formation on microbial community structure and its implications for GHG dynamics in a highly degraded permafrost valley (Nunavik, northern Quebec, Canada). Samples were collected from a palsa, an emerging lake connected to the palsa, surrounding peat and soil pore water, and two mature lakes which are older, stratified, and less connected to the palsa.