Carbon, nitrogen, and sulfur isotope changes and hydro-geological processes in a saline lake chain

Abstract

The ionic concentrations,conductivity and pH of water in the Lake Chany complex in West Siberian Russia change from the mouth to the interior of the lake. This difference is indicative of marked evaporation of lake water from the closed water body system in the dry climate of Western Siberia. The carbon isotope composition of particulate organic matter (POM, composed mainly of phytoplankton) clearly changes, along with the pH of the water, reflecting the concentration of dissolved CO2. Carbon and nitrogen isotope signatures of Chironomus plumosus larvae, a benthic invertebrate that may feed on bulk lake sediment, systematically increase, along with those of POM and sediment organic matter (SOM), through the lake chain. Both sulfate-sulfur and nitrogen isotope compositions of the POM and SOM increase with distance from the estuary into the Lake Chany complex. Heavier sulfur and nitrogen isotope recycling from the sediment, caused by microbial sulfate reduction and denitrification, respectively, may have led to the increased sulfate-sulfur and nitrogen isotope compositions of the POM and SOM.