Biogeochemistry of glacial lakes in western Norway: Comparison to other regional lakes and impacts of an extreme hydrological event

Glaciers can affect the biogeochemistry of associated freshwater systems; however, there is substantial spatial and temporal variability in these effects. We assessed the biogeochemistry of proglacial lakes connected to Jostedalsbreen, a rapidly changing ice cap in western Norway that has declined in area and mass since the end of the Little Ice Age. We measured heavy metals and nutrients in four glacially fed (GF) and three nearby snow and groundwater-fed (SF) lakes during September 2023. Nutrients—total phosphorus (TP) and nitrate (NO3−)—and some heavy metals (Pb, Cr, Al, Fe, Co) were elevated (107 percent and 158 percent, respectively) in GF compared to SF lakes. In contrast, the metals As and Cd were higher (70 percent) in SF compared to GF lakes. We also investigated the geochemical effects of an extreme flood event in one GF lake, and we found all metals, two major ions, TP, and turbidity were higher 1-day post-flood compared to 24-days post-flood. Our results show that the geochemistry of GF lakes differs from nearby SF lakes, and rising meltwater fluxes may increase metal and nutrient concentrations in GF lakes. Additionally, extreme precipitation can contribute large amounts of metals to aquatic systems, potentially affecting local and downstream biota.