Analysis of the Phytoplankton State in Low Mountain Lake Manzherokskoye (Gorny Altai) using Hydro-Optical and Hydro-Physical Characteristics

The composition, development, distribution of the phytoplankton as well as the hydro-optical and hydro-physical characteristics were studied in the eutrophic-polytrophic, low-flow, low-mountain, ancient lake Manzherokskoye (Altai Republic) in April and July 2021. In the subglacial period, with an ice thickness of 0.45–0.50 m and a thin snow layer with thaws, a water temperature of 0.1–4.6°C, 29 taxa with a rank below the genus vegetated. Their abundance reached: biomass – 15.9 g/m (mean value 11.5 g/m), Chl content 2.79 mg/m, Chl – 58.11 mg/m, Chl – 35.81 mg/m. Summer phytoplankton at a temperature of 24.2–25.5°C was characterized by higher taxons (72), biomass 7813.3 g/m (mean value 1960.4 g/m), Chl content 16.82 mg/m and by lower Chl – 10.87 mg/m and Chl – 30.54 mg/m. The strongest dependence of optical indicators on the abundance of algae was noted between the light absorption coefficients with wavelengths of 520, 550, 580, 610 nm and cyanobacteria biomass, between the light absorption coefficient with wavelength of 460 nm and the total biomass of green and euglenic algae.