LANDSCAPE AND MICROBIAL CONTROLS ON LAKE GEOCHEMISTRY IN SW GREENLAND

Arctic lake geochemistry is changing rapidly due to altered temperature/precipitation regimes that affect the flows of elements into lakes and their subsequent biological processing. Here, we examine regional vs. local controls on dissolved and particulate lake geochemistry in six hydrologically isolated lakes near the Greenland Ice Sheet. Elemental inputs into lakes are dominated by regional minerogenic dust deposition, which has increased with enhanced glacial activity since the Little Ice Age (~1850 CE), stimulating microbial production and elemental immobilization. Dust deposition rates decrease with distance from the ice sheet, and differential leaching and organic matter sedimentation rates have led to the accumulation of base cations in lake sediments closer to the ice sheet vs. higher burdens of metals and sulphur in more distant lakes. Dissolved elemental patterns show inverse patterns due to evaporative concentration of cations, differential weathering of silicates vs. carbonates, and redox-dependent/microbial processing of metals and sulphur. Together, these results highlight the heterogenous responses of lakes to global change drivers and the interactive controls of physical, chemical, and biological processes on biogeochemical cycling and storage in Arctic drylands lakes.