Phytoplankton is dominated by cryptophyte flagellates Rhodomonas sp. and green-coloured cocci. In the coloured layers, the following pigments were detected by spectrophotometry: chlorophyll a, chlorophyll b, bacteriochlorophyll c or g, and phycoerythrin. Therefore, the presence of cryptophytae algae (genus Rhodomonas), unicellular phototrophic organisms containing chlorophyll b, and green sulfur bacteria is shown. The distribution of the layers: 0 - 1.7 m: organisms are virtually absent; 1.7- 2.2 m: cyanobacteria; 2.2 - 2.4 m: light absorption peaks corresponding to phycoerythrin and chlorophyll a and b appear, a large number of cryptophytae algae (genus Rhodomonas) and unicellular green algae. 2.4 - 2.7 m: concentration of pigments decline, a small amount of cells with chlorophyll b and cryptophytae algae; 2.7 - 4 m: green sulfur bacteria.

For the first time, a theoretical explanation of changes in the lake Kislo-Sladkoye following a spring tide is given. Densities of seawater and lake water were calculated and the results show that seawater penetrated the lake at a depth of 1.55 m during the spring tide.