This study presents a biomonitoring study of surface waters in the Krynka River basin, encompassing three major regional reservoirs: Khanzhenkovskoe, Olkhovskoe, and Zuyevskoe. These water bodies face significant anthropogenic pressure from mining effluents, industrial discharges, and domestic wastewater. Key pollutants identified are surfactants (SAAs), sulfates, phenols, chlorides, and manganese, with chemical oxygen demand (COD) exceeding regulatory limits. The research was conducted in September 2024. Based on the Specific Combinatorial Water Pollution Index, surface waters in the studied objects can be characterized as slightly polluted. To assess the negative impact of the identified pollutants on hydrobionts, the species composition of phytoplankton of the studied water bodies was analyzed. In the Olkhovskoe Reservoir and Olkhovaya River, cyanobacterial blooms (Oscillatoria agardhii G.) were observed, altering biodiversity in the Krynka River and Zuyevskoe Reservoir. Phytoplankton genera Synedra, Amphiprora, and Navicula—established bioindicators of aquatic ecosystem health—were dominant in Khanzhenkovskoe Reservoir, signaling nutrient enrichment and organic pollution. Changes in the species composition and structure of phytoplankton in the Krynka River, its tributaries and reservoirs, indicate a change in the level of saprobic water bodies from β to α-mesosaprobic, which indicates both the general level of surface water pollution and the accumulation of pollutants along the course of the river. The paper presents the results of fluorimetric analysis of photosynthetic activity of natural phytoplankton cells and demonstrates the possibility of using fluorescence induction curves for regular monitoring measurements. Fluorescence parameters indicate a general deterioration of photosynthetic activity of natural phytoplankton. The growth of Oscillatoria agardhii in the waters of the Olkhovskoe Reservoir and of green microalgae in the Zuevskoe Reservoir led to an increase in the fluorescence quantum yield (F_v/F_m) and the total photosynthetic activity index (PI), which makes it possible to use these parameters as indicator parameters reflecting the intensity of “blooming” of various phytoplankton species.

The article examines the state of the drinking Volyntsevo reservoir and its tributaries in conditions of significant changes in the hydraulic regime and pollution by waste mine waters. The state of algoflora of a water body is considered, the results of studying the species composition of phytoplankton, the content of basic photopigments and photosynthetic activity of microalgae are presented. The study presents the results of the application of the method of fluorimetric assessment of the state of phytoplankton cells as the main bioindicator of the state of the aquatic environment. The research was conducted in the vicinity of Yenakievo for the Volyntsevo reservoir and the Bulavin river. These water bodies are subject to significant man-made impacts: as a result of intensive water use of reservoir resources, there has been a significant decrease in water levels and, as a result, a deterioration in water quality. The conducted studies have shown a significant excess of the permissible standards for the content of magnesium ions, sulfates, total hardness and alkalinity in water samples. The negative impact of surface water pollution on the species composition of algoflora, as well as the photosynthetic activity of phytoplankton cells, has been shown. The obtained materials can serve as a basis for further monitoring of drinking reservoirs in the region. The current situation requires constant monitoring observations aimed at identifying and eliminating all sources of pollution of the studied water bodies.

In order to determine the condition of drinking water sources in Donetsk Region and assess potential threats related to water pollution from mining and industrial wastewater, it is extremely important to monitor surface waters, which should include an assessment of the condition of gydrobionts. Additionally, declining surface water quality in the region contributes to pollution in the coastal waters of the Sea of Azov. This study presents the monitoring results for the southern part of the Kalmius River basin. Analysis of water samples revealed contamination by phenol, sulfates, chlorides, anionic surfactants, iron, elevated water hardness, and significant exceedances of suspended solids and total dissolved solids. The iron concentration at the Kalmius River estuary reached 0.81 mg∙L⁻¹, exceeding the permissible limit by 2.5-fold. Sulfate and total dissolved solids concentrations attained 1673 and 160 mg∙L⁻¹, respectively. Changes in the species composition of phytoplankton were observed in response to variations in iron, manganese, and phenol concentrations in the water. Specifically, elevated iron levels led to increased abundance of the metal-sensitive species Cyclotella meneghiniana Kützing. Principal component analysis of the data revealed a relationship between increased phenol concentrations in the aquatic environment and a mean 20% reduction in phytoplankton cell photosynthetic activity, as well as the influence of manganese ions on cell abundance and photopigment content. Thus, phytoplankton cell fluorescence, alongside shifts in species composition and photosynthetic pigment content, can serve as an additional indicator of surface water pollution by iron and phenol.

The article considers the possibility of using fluorimetric analysis of photosynthetic activity of phytoplankton in assessing the toxicity of natural water samples by biotesting on Chlorella vulgaris culture. The study assessed the toxicity of water samples from the Krynka River, its tributaries – the Olkhovka and Olkhovaya Rivers, as well as the Khanzhenkovskoye, Olkhovskoye and Zuyevskoye Reservoirs, which are sources of water resources for the region. The inclusion of a fluorimetric assessment of the photosynthetic activity of phytoplankton cells using chlorophyll fluorescence induction curves makes it possible to study in more detail the change in the state of the test object. Biotesting was performed on a culture of green microalgae Chlorella vulgaris. The study revealed a decrease in the fluorescence intensity and photosynthetic index of algae cells when cultured on filtrate from all monitoring points. Acute toxic effects have been established for water samples from the Khanzhenkovskoye and Olkhovskoye Reservoirs, as well as chronic toxic effects for the Zuyevskoye Reservoir. The deterioration of surface water quality in reservoirs is associated not only with the ingress of mine waters, but also with intensive water use, which leads to a significant decrease in water levels and the death of aquatic organisms. The results obtained can become the basis for further monitoring studies of surface waters in order to identify and eliminate factors that have a negative impact on rivers and reservoirs in the region.

The article discusses the possibilities of using methods for recording light and induction curves of chlorophyll fluorescence of test-culture Chlorella vulgaris in biotesting of water samples. The results of biotesting of water samples from the Volyntsevo reservoir and its main tributaries are presented. The data are presented for the period of active use of reservoir resources, which led to a significant decrease in water levels and deterioration in the quality of water resources. Studies have shown the presence of chronic toxic effects of samples from the reservoir on the test object under study. The filtrate of water samples from the northern tributaries of the Volyntsevo reservoir had a stimulating effect on phytoplankton culture. The methods of fluorimetric analysis confirm the results of the biotesting technique, are consistent with changes in the number of cells and the content of chlorophyll in the samples, and also reveal a negative effect on the photosynthetic apparatus of Chlorella vulgaris, which does not cause changes in the parameters of the growth of the test culture. The negative impact of water samples from the main tributary of the reservoir, the Bulavin River, on the speed of electronic transport and the functioning of primary electron acceptors of photosystem II of Chlorella vulgaris cells was revealed. The obtained materials can be useful for researchers dealing with the problems of biophysics of primary photosynthetic reactions, environmental monitoring of surface natural waters and biotesting.

Pollution of rivers and large water bodies, including reservoirs, by wastewater from various sources is one of the most critical issues in the Donetsk region, requiring continuous monitoring and assessment of surface water quality. The research aims to assess the state of the Kalmius River under anthropogenic pressure, as well as to find correlations between the species composition, photosynthetic activity of phytoplankton, and the degree of water pollution. This study presents the results of biomonitoring of the Kalmius River and its tributaries within Donetsk City, which are under intense anthropogenic pressure. Pollution of the river channel by phenol, anionic surfactants, Ferrum ions, chlorides, and sulfates was identified. Based on the combinatorial pollution index, the water in the Kalmius River and its tributaries can be classified as polluted. The pigment composition of water samples was analyzed, and the species composition of river phytoplankton was determined. Dominant species include Chlorella vulgaris Beij., Dictyosphaerium pulchellum H.C.Wood, Scenedesmus quadricauda Brébisson, and Oscillatoria agardhii M.A.Gomont. Photosynthetic activity of the river’s algal flora was assessed based on chlorophyll fluorescence induction curves of natural phytoplankton. A correlation was established between surface water pollution levels and changes in the photosynthetic apparatus of microalgae cells. A strong negative correlation was found between the content of nitrate nitrogen in the aquatic environment and the photosynthetic activity, pigment composition, and abundance of the main dominant forms of phytoplankton, particularly the microalgae of the genus Cyclotella. The data obtained shows that the Kalmius River’s pollution has a significant impact on phytoplankton biodiversity, leading to the growth of cyanobacteria species.