25 samples from the lake Bayan Nuur sediment core ( BN2016-1) bottom sediments were processed for diatom analysis in the range from 0 to 110.4 cm (Appendix 2). The samples of sediments were treated using the water bath method. We used high refracting Naphrax resin for the preparation of slides. The species were identified by key books. The valves were counted by parallel transects up to 300 pieces in a sample, using a light microscope and immersion oil. The total number of valves was considered to be 100%. Dominant species were defined as those which accounted for 10% of the total amount or more; subdominants were species which accounted for 5–10%. The pH and total phosphorus (µg/l) values were reconstructed using the European diatom algae database. The trophic status was assessed according to the reconstructed value of total phosphorus. Biogeographical and ecological characteristics of the taxa concerning preferences of habitat, pH, water salinity, geographical distribution were described following Van Dam et al. (1994, doi:10.1007/BF02334251) and Barinova et al. (2006).