ИСТИНА

Stratified lakes are water bodies where water masses do not mix for an extended period due to differences in density. This phenomenon allows for the study of the light climate relevant to the specific composition of phytoplankton developing in a particular water mass with difficult-to-overcome boundaries. Therefore, in such water bodies, the structure (composition and abundance) of phytoplankton is influenced, among other factors, by the spectral characteristics of light as well as the overall intensity of solar radiation. In this study, we present the results of our research on the structure of phytoplankton concerning the light climate conditions at different depths of Lake Skurcha (Republic of Abkhazia). Phytoplankton samples were collected at the end of January 2025, and the spectral composition of light was determined using a submersible spectrometer, while light intensity was measured with a lux meter. Overall illumination in the lake sharply decreased at depths of 1.5 m and 3.5 m, reaching 100 lux at a depth of 4 m. The light spectrum at 3 m shifted toward longer wavelengths, with a peak at 590 nm at a depth of 3.5 m. A significant influence of the spectral composition of light on the structure of phytoplankton was demonstrated, while the intensity of light did not have a similar effect.