Sources, distribution and biogeochemical cycling of dissolved trace elements in the coastal lakes of Larsemann Hills, East Antarctica

Highlights: • Trace metals are at natural background level with no anthropogenic influence. • Dissolved PO₄⁻³ and Mo are found as limiting nutrients for primary productivity. • Dissolved Cu supports bacterial mediated organic decomposition in the lakes. • Removal of dissolved Ba and their accumulation in sediments are widespread. Coastal lakes in Antarctica receive an enormous amount of ions and trace elements (TEs) during the austral summer. Some of these TEs and ions are utilised as essential nutrients in primary productivity. In the present study, selected dissolved TEs (Ba, Mn, Cu, Co, Cd, Mo and U) along with dissolved organic carbon (DOC) and Chlorophyll-a were studied in ten coastal lakes of the Larsemann Hills, East Antarctica to decipher their (TEs) sources, understand geochemical behaviour and assess their role on nutrient dynamics. Dissolved concentrations of these TEs are in sub-nanomolar range; almost an order of magnitude lower than the average seawater and global river concentrations. Sea-salt spray and chemical weathering in the catchments of these lakes are dominant sources for these TEs and ions. Though most of the Antarctic lakes have been reported for their oligotrophic character, however, a significant amount of DOC and Chlorophyll-a, and occurrence of algal mats in some of the LH lakes indicate seasonal (austral summer) productivity with the availability of sunlight and nutrients. Our investigation reveals that phosphate (PO₄³⁻) and Mo act as limiting nutrients because of their lower concentrations in the water column. Dissolved Cu plays an important role in bacterial-induced organic matter decompositions and release of organic carbon to lake water. We also found Ba excess (non-terrigenous) in the lake and catchment sediments varying from 26 to 63%. The higher Ba_excess in the catchment sediments could be due to significant removal of dissolved Ba during the solute transport and later supplied to these lakes. The geochemical data sets presented in this study were found at a natural background level and therefore, would be useful for comparison with other global aquatic environments. Findings of the present study improve our understanding about the biogeochemical cycling of trace elements and their critical role in oligotrophic lakes of Antarctica.