Nutrient cycling and productivity in Antarctic lakes

Abstract

Sedimentary organic matter from the Antarctic lakes is the source of various proxies used to study productivity changes. A total of three sediment cores (GL-1, V-1, and L-6) collected from the lakes of Schirmacher Oasis, East Antarctica, were analysed for total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), biogenic silica (BSi) and their ratios were computed to understand the nutrient cycling and productivity in Antarctic lakes. In core GL-1 and V-1, high TOC and high clay in the upper section of the core indicated high primary productivity due to the lakes' exposure to the ice meltwater influx. The C/N ratio of substances GL-1, V-1, and L-6 varied from 2.72 to 8.52, indicating the source of organic matter as autochthonous exclusively derived from algae (C/N less than 10). N/P ratio is less than 7.81 in all three lakes, meaning a potential limitation of N in all the lakes. In cores GL-1, V-1, N/Si ratio is lower than 1, indicating N limitation, while in core L-6, N/Si ratio is higher than 1, i.e. 1.53, indicating Si limitation. Si/P ratio is found to be greater than 3 in all the cores, indicating P limitation. Deviation from the Redfield ratio suggested that the lakes are oligotrophic.