Dynamics of the Concentration of Biogenic Elements and Phytoplankton in the Littoral Zone of Lake Baikal in 2021–2023

The results of a study of the dynamics of biogenic elements, chlorophyll, biomass, and phytoplankton abundance in the littoral zone of Lake Baikal in June and September 2021–2023 are presented. No consistent differences in the content of mineral forms of nitrogen and phosphorus have been found in different areas of the littoral zone with different anthropogenic loads. It is shown that the coastal areas near human settlements were characterized by high phytoplankton concentrations, as well as by high total nitrogen and total phosphorus with a predominance of organic forms. The influx of water from large tributaries increased the silicon content in littoral areas of the lake that are adjacent to the mouth. The spring subglacial phytoplankton complex began to grow during the maximum annual content of biogenic elements. The summer algal community developed at lower concentrations of mineral nitrogen and phosphorus; its development led to a decrease in the amount of phosphates, up to their complete depletion, as well as to a decrease in the concentration of nitrates and the appearance of nitrites and ammonium in September. Interannual variations in the content of biogenic elements are insignificant during certain periods of measurements. The concentrations of silicon, total nitrogen, and total phosphorus and their mineral forms have not changed compared to previous studies. With respect to the TSI and TLI indices and total algal biomass, the trophic status of the littoral zone of Lake Baikal corresponds to the oligotrophic level with eutrophic elements in June and mesotrophic features in September.