Eutrophication of Surface Water Bodies and Ways of Its Reduction (a Review)

Results of studies on eutrophication of surface waters as one of the negative phenomena of the functioning of aquatic ecosystems are summarized in the article. It is noted that eutrophication is a complex process caused by the influence of a number of factors, primarily an increased content of nutrients, in particular nitrogen and phosphorus compounds. The criteria for assessing the trophic state of water bodies and watercourses using chemical, biological and physical parameters, as well as complex indices of trophic state based on them, are presented. External and internal sources of nutrient input to the aquatic environment are considered. It is shown that the input of nitrogen and phosphorus compounds from bottom sediments should be considered as a powerful internal source of eutrophication. Considerable attention is paid to the analysis of the causes of nutrients' release from bottom sediments. It is emphasized that intensive algal blooms negatively affect a number of hydrochemical parameters causing a significant decrease in the content of dissolved oxygen up to its deficiency and the formation of hypoxia and anoxia. The production of cyanotoxins during excessive algal blooms results in the increase in the toxicity of the aquatic environment and adversely affects the state of biota and human health. The potential impact of climate change on the level of eutrophication of water bodies is discussed. The most common methods of reducing eutrophication are provided, which involve limiting the external input of nitrogen and phosphorus compounds to water bodies, as well as their migration from bottom sediments.