Comprehensive assessment of the ecological state of the flood-plain lake Kholunovo by chemical and biological indicators

Lake Kholunovo (Kirov region, Russia) is a natural monument of regional importance, located in the floodplain of the Vyatka River, the largest river in the region, in the vicinity of the administrative center of the region - the city of Kirov. In the summer season of 2022, a route inspection of the lake was carried out, a physical and chemical analysis of water samples, biotesting and a study of phytoplankton were performed. It is noted that according to hydrochemical indicators, the water in Lake Kholunovo belongs to the group of slightly polluted waters. With depth in the lake, the concentration of ammonium nitrogen increases, the content of oxygen dissolved in water and the pH value decrease. These factors influence the toxicological properties of water. At a depth of 2.5 m and in the bottom layer, the water in the lake is toxic to the test organisms Paramecium caudatum and Escherichia coli . The species composition of the algocyanoflora of the floodplain lake Kholunovo reflects the ecological state of the reservoir. The phytoplankton of the lake is characterized by the dominance of green algae, indicators of weak water pollution, and the predominance of beta-mesosaprobiont species. Since the lake does not experience technogenic load, but is used only for recreation and fishing, it is proposed to consider this reservoir as a background when studying similar lakes in the Vyatka River valley that are experiencing technogenic load.