Introduction

Northern freshwater ecosystems are undergoing rapid change in response to climate-related permafrost thaw (e.g., Littlefair et al. 2017, Zolkos et al. 2022). Freshwater systems (e.g., lakes & rivers)  facilitate the cycling of carbon and nutrients between different reservoirs, including land, water, and atmosphere (e.g., Tranvik LJ et al. 2009). These processes are closely tied to the interactions between freshwater systems and their surrounding landscape (figure 1). In northern regions, the presence of permafrost (figure 2) influences freshwater biogeochemistry by impacting hydrological pathways and surrounding vegetation (e.g., van Everdingen RO, 1981; Standen KM & Balzter JL 2021).  

With rapidly accelerating climate change in high latitudes driving permafrost thaw (Kokelj SV et al. 2015), northern lakes are subject to changing land-water interactions.  Thawing permafrost often results in the erosion and deposition of terrestrial materials into nearby aquatic systems, such as through collapsing lake banks (figure 3). The development of thermokarst features, lakes or other landforms created from thawing permafrost, can drive shifts in aquatic biogeochemistry and biological community composition (Crump BC et al. 2003; Kokelj SV et al. 2005). 

The influx of terrestrial material into aquatic systems creates new environments that may have a different ability to support microbial activity. Microbes are responsible for the production and emission of greenhouse gases (i.e., carbon dioxide and methane) as a byproduct of decomposing organic matter. The volume and type of gas released are dependent on the organic matter present in the system and the microbial community supported by the environment. As permafrost thaws, there is concern that the carbon stored in permafrost will be transformed into greenhouse gases, contributing to climate change. However, these emissions are dependent on microbial activity in northern regions and the presence of specific environmental conditions.