Athalassic lakes in Yukon (Canada) respond sensitively and differentially to long-term climate variability

Northern athalassic (inland saline) lakes may be especially responsive to climate warming yet are understudied relative to freshwater ecosystems. Here, we use dated sediment cores to assess how two athalassic lakes in central Yukon (subarctic Canada) responded to ∼100 years of climate variability compared to a freshwater site. The athalassic lakes responded to moderate drought (1927-1945) and wet (1958-1966) conditions, but biological change differed between the subsaline (vertical salinity gradient from 2.2 – 4.2 ppt) and hyposaline (3.7 – 24 ppt) sites. Throughout the drought, cladocerans and cyanobacteria became scarce in the hyposaline lake, likely due to salinity stress, and did not recover. In contrast, most biological proxies in the subsaline lake were relatively stable until the wet period when lake production increased and likely stimulated pelagic cladoceran growth under tolerable osmotic conditions. However, paleosalinity in the subsaline lake decoupled from climate in the early 1970s and instead appeared governed by catchment processes, including erosion and hydrological changes after a 1969 wildfire. In contrast, the freshwater reference site has remained relatively stable since the early 1900s. These data highlight athalassic lakes as sensitive paleoclimatic recorders and demonstrate how site-specific factors within their catchment mediate their response to climate change.