Assessment of the ecological status of the river water system in European North under conditions of ultra-fresh humus waters using biotic indices (Suna River, Lake Onega Basin, Russia)

Protecting rivers and lakes from pollution is crucial for maintaining the health of aquatic ecosystems and ensuring the well-being of both wildlife and humans. Present study intends to examine the water quality of the Suna River (Eastern Fennoscandia in the European North of Russia) to assess the ecological risk. Widespread methods for assessing water quality based on macrozoobenthos and phytoperiphoton were applied. It was found that in conditions of ultra-fresh waters with high humus content, biotic indicators may indicate pollution of water bodies that do not actually experience significant anthropogenic impact. Ratings ranging from ‘poor’ to ‘excellent’ were obtained for different stations, reflecting the influence of natural features of different sections of the river. ‘Good’ water quality was noted at the river stones biotopes. In river gravel, sand and silt biotopes, as well as all lake biotopes, ‘mediocre’ water quality was found. The low anthropogenic income on the river catchment allows us to conclude that most indices for assessing water quality significantly underestimate the results in the natural conditions of Eastern Fennoscandia. Biotic indices EPT, BBI and EBI are most accurate for assessing the water quality of rivers and lakes in Eastern Fennoscandia. HIGHLIGHTS An assessment of the ecological state of the freshwater ecosystem in the North of Russia has been carried out.; Macrozoobenthos and periphyton can be indicators of the state of the environment.; The anthropogenic factor is important in the formation of a high-quality aquatic environment.; Water quality is determined by the degree of the impact on the ecosystem.; Very low water mineralization and high humus content make it difficult to determine the ecological status of rivers and lakes.;