PHYTOPLANKTON OF A SMALL RIVER AS AN INDICATOR OF WATER QUALITY IN THE CONDITIONS OF CLIMATE CHANGE AND MILITARY ACTIONS ON THE TERRITORY OF UKRAINE

Abstract

The work discusses some topical issues of water quality assessment of small watercourses under the conditions of climate change and military operations on the territory of Ukraine, using the example of the Tal River (Kyiv region, Borodyanskyi and Ivankivskyi districts). The data obtained during the growing seasons of 2023–2024 regarding the structural-functional and indicator characteristics of watercourse algae were compared with the information obtained in 2004–2005. At the current stage of functioning of the river ecosystem in the phytoplankton of the Tal River, 42 species and intraspecific taxa of algae with the nomenclatural type of the species, including 9 divisions, were found. According to the composition of the leading taxa, it is green-diatom-euglenous. Impoverishment of the species composition of river phytoplankton over the past 10 years was established, primarily due to a noticeable decrease in the share of diatoms (from 27 species to 9). The impoverishment is most likely due to the increase of negative anthropogenic influence, as well as climatic changes. A simplification of the taxonomic structure of phytoplankton was also established, as indicated by a decrease in the genus coefficient over time. In the structure of phytoplankton of the river, the leading role belonged to planktonic and benthic inhabitants, planktonic, benthic and soil forms had a smaller representation in the composition of algal communities. The presence of a significant share of benthic species in the composition of plankton is due to the peculiarities of shallow areas of small rivers, which are characterized by wind mixing and, as a result, separation of benthic and soil forms. The presence of a significant share of benthic species in the composition of plankton is due to the peculiarities of shallow areas of small rivers, which are characterized by wind mixing and, as a result, separation of benthic and soil forms. According to the temperature limitation, most of the indicator species belonged to eurythermic species, the share of thermophilic species was also noticeable, which is probably the result of global climate changes. In terms of rheophilicity, stagnant-flowing (slowly mobile) species prevailed – indicators of moderately oxygenated waters, 33% belonged to stagnant forms with relatively low oxygen saturation, which corresponds to the place of phytoplankton existence – a shallow river with a low intensity of photosynthetic aeration Most species of planktonic algae r. Thallus are freshwater forms. The presence of salt-loving forms (halophilic oligohalobes, mesohalobes) is the result of increased mineralization as a result of drying, which leads to a change in the diversity of algae and is one of the climatic factors that affects the formation of the algoflora of the Ukrainian Polissia. In relation to pH, indifferents prevailed i n the Tal River, while the proportion of acidophiles (13%) was also noticeable, which indicates a moderate effect of acidification and slight acidification processes. It was found that the vast majority of watercourse algae according to saprobicity belong to the III class of water quality – «water of satisfactory quality».