Diversity of species of higher aquatic plants of Lake Somivka (Dniprovsko-Orilskyi Nature Reserve)

The hydroecological properties of lakes in river floodplains are variable and are determined by the influence of a number of indicators, among which the hydrochemical properties of the soil, the number of floods, and the physicochemical parameters of the aquatic environment are important. Floodplains are very sensitive to changes, especially to the regulation of riverbeds, drainage, and pollution. Preservation of them in a natural state is important for ecological balance. Higher aquatic plants influence the processes occurring in water bodies, change their physicochemical properties, and determine the level of eutrophication of water bodies. In the summer, most of the hydrochemical parameters of water change due to the increase in temperature, while the oxygen level in water decreases from 7,2 to 6,4 mg/l, and the level of permanganate oxidation increases from 7,3 to 11,4 mg/l. Water transparency decreases to 0.1–0.2 m. When coastal areas of water bodies, such as, Scirpus lacustris L., Alisma plantago-aquatica L., Stratiotes aloides L., various types of sedges, the above processes are intensified, which causes changes in the natural properties of ecosystems as a whole. Aloe water cutter rapidly, forming dense thickets that can crowd out other aquatic plants, water chestnut, which in moderate quantities contributes to ecological balance, but with excessive growth can disrupt the oxygen balance and contribute to waterlogging of the reservoir. Among hydrophytes, the development of Salvinia natans L. is stable, the number of which almost does not change in the studied water area. At the initial stages, the sedge helps to stabilize the ecosystem by absorbing excess nutrients. Floodplain lakes have a dynamic phytoplankton composition that changes depending on the season and the ecological state of the reservoir, therefore the species diversity of phytoplankton, the number of systematic groups are variable. The phytoplankton of Lake Somivka is represented by eight systematic groups, among which the dominant ones are blue-green with a significant predominance of 14348 individuals/m3 and diatom algae. Polluted and eutrophicated bodies of water are dominated by cyanobacteria, which can release toxins and lead to oxygen deficiency.