Isotopic variations of organic carbon and carbonates in bottom sediments and microbial mates of mineral lakes in Zabaikalsky krai

We have studied isotope variations of organic carbon and carbonates in bottom sediments and microbial mats of mineral lakes of Zabaikalsky Krai. Organic carbon (d13Corg) in bottom sediments of the studied mineral lakes ranges from -22.28 to -30.12 %o, carbonates (d13Corg)- from -5.60 to -12.15 %o. A wide range of variations in d13Corg indicates that bottom sediments of mineral lakes inherit the isotopic composition of the primary producers of organic substance. In production processes, microorganisms of mineral lake mats use carbon dioxide, which differs in the carbon isotopic composition. Cyanobacteria in the microbial mats of mineral lakes use carbon dioxide of biogenic origin to synthesize organic substance. High pH values in combination with high concentrations of salts up to saturating levels make mineral lakes unique ecosystems. The arid climate and high solar activity favor the evaporation of water and formation of highly mineralized lakes. A specific feature of these lakes is alkaline conditions and high concentration of salts [Syrenzhapova, Abidueva, Dagurova et al., 2023]. There are more than 100 large and small lakes in Zabaikalsky Krai, among which mineral lakes are often found. They are mainly located in flat basins, have a predominantly round or oval shape, the water level depends on the amount of precipitation. Some of them dry out during dry times. The article is aimed at studying isotope variations of organic carbon and carbonates in bottom sediments and microbial mats of mineral lakes of Zabaikalsky Krai.