Limnology and diatom ecology of shallow lakes in a rapidly thawing discontinuous permafrost peatland

Lakes in discontinuous permafrost peatlands are on the front lines of climate change, sensitive to even modest increases in air temperature. The aim of this study was to provide the first limnological characterization of shallow (∼1-2 m depth) lakes in the Scotty Creek basin (Northwest Territories, Canada), a field site of circumpolar significance due to the existence of long-term ecohydrological monitoring going back decades. We use this as a foundation from which to advance our process-based understanding of the potential drivers of lake ecosystem change. Our results showed that dissolved organic carbon (DOC) and lake color were not correlated, a pattern that appears to be an important driver of diatom (siliceous single-celled algae) assemblages in these lakes. Diatoms in the study lakes tended to fall into one of two assemblage clusters. One cluster, comprised of small benthic Fragilariaceae and small Navicula species (sensu lato), was found associated with higher lake color. The second cluster, comprised of Encyonopsis and large Navicula species, was found associated with high DOC, lower color, and the presence of a benthic moss mat. From this, we suggest that DOC quality is a primary control on lake ecology in this region for its role in controlling light penetration to the lake bottom. We hypothesized that the prevalence of nearshore fens and collapse scar wetlands would be important drivers of DOC, but this was not supported in the 9 study lakes for which we had available data to map shoreline features.