CHARACTERISTICS OF THE HABITAT CONDITIONS OF AQUATIC BIORESOURCES IN THE MIUS RIVER IN 2024

Background. The study of the hydrochemical and toxicological status of the Mius River is of great ecological and fisheries importance. Relevance. The high anthropogenic pressure on the Mius River, as well as insufficient knowledge of this water body in the modern period dictate the need for a comprehensive analysis of the habitat of aquatic biological resources. The aim of this work is to investigate the habitat conditions of the aquatic biological resources of the Mius River in 2024. Methods. Hydrochemical and toxicological studies of the water and bottom sediments of the Mius River were conducted in the river section spanning from the city of Miusinsk to the river confluence with the Mius Estuary (Liman) in August and November of 2024. Hydrochemical analysis involved the determination of dissolved oxygen, pH, ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, phosphates based on phosphorus, total mineralization, calcium ions, sulfate ions, and chloride ions. Toxicological analysis of water and bottom sediments has also been conducted and involved the determination of heavy metals (mercury, lead, cadmium, arsenic, iron, manganese), polychlorinated biphenyls (PCBs), and petroleum products. Results. The oxygen regime and concentrations of biogenic elements in the Mius River and the Mius Estuary (Liman) were favorable for hydrobionts. Based on the salt content, the water was characterized as slightly brackish in the Mius River and brackish in the Mius Estuary (Liman), with prevalence of sulfate ions (highly likely due to the influence of mine waters), an increase in chlorides in the lower reaches of the river, and calcium content sufficient for the development of fish. It is highly probable that the increased concentrations of iron and manganese in the water had a natural origin. It is also possible that the mercury was introduced into the water from a natural source. Increased concentrations (up to 3.4 MPCfishery) of petroleum products with high resinous substance content were recorded in the water of the lower reaches of the Mius River. In the bottom sediments of the middle and lower reaches of the Mius River, high concentrations of petroleum products exceeding the threshold level by up to 12 times could exert an adverse effect on the development of bottom communities. Conclusion . In general, the aquatic environment of the Mius River and Mius Estuary (Liman) in 2024 could be considered as relatively favorable for hydrobionts. The quality of aquatic biological resources (namely, crucian carp) met the regulatory requirements for food products.