Long-Chain Alkenones in Saline Meromictic Lakes of the North Minusinsk Depression (Southern Siberia): First Knowledge and Possible Correlation with Water-Level Dynamics

Long-chain alkenones (LCAs)-lipides produced by some microalgae of the Haptophyta group in seas and continental water bodies-are promising paleomarkers of climate changes because they are well-preserved in bottom sediments. The hydrocarbon chain and the degree of unsaturation of double bonds of this class of lipides can vary depending on habitat conditions of their producers. For the first time, we have discovered LCAs in the bottom sediments of two saline meromictic lakes Shira and Uchum located in arid steppes of southern Siberia (the North Minusinsk Depression) and estimated the distribution of their total content, length, and the degree of unsaturation. The highly abundant population of producers of LCAs-haptophyte algae of the genus Isochrysis (Haptophyta)-is revealed in the water column of Lake Uchum. It is shown that the species composition of the haptophyte algae and composition of the LCAs in the lakes under study are similar to those in saline stratified lakes of North America (Saskatchewan, Canada) with a similar climate and salt composition. The abundance of the C37:4 alkenone in the bottom sediments in the last 100 years reflected the variations in lake salinity caused by the documented changes in the water level. In this way, it is shown that the LCAs may be used as a paleomarker of climate-driven changes in the water level of the saline lakes in southern Siberia.