Since the second half of the 20th century, the influence of anthropogenic factors on the natural environment has increased significantly. As a result, various local, regional and national environmental problems began to arise. This leads to a change in the flora and fauna living in the regions, as well as to the complete disappearance of some species from the face of the earth. Therefore, time itself dictates the need for a deeper study of plants in the regions, the environmental factors affecting them.

    There is an impact on the ecological state of the aquatic ecosystems of the middle Zarafshan and the processes of change occurring in them, in particular, the species composition of hydrobionts living in reservoirs, rivers, canals and fish farms. In this regard, the study of the fauna and ecology of hydrobionts in the aquatic ecosystems of the middle Zarafshan, the development of protective measures are among the topical issues of great scientific and practical importance.

    Based on these questions, the main goal of my research is a comprehensive study of the fauna and ecology of hydrobionts in the aquatic ecosystems of the middle Zarafshan. In addition, we are aimed at an in-depth study of parasitic and beneficial species contained in hydrobionts, identifying the ranges of rare, endangered species, developing protective measures, studying ways of quantitative and territorial reproduction of populations of promising, economically significant species.

    Given that the systematic composition of hydrobionts of various types of waters of the Zarafshan River, their bioecological features, interbiotope distribution, ecology and other important aspects have not been fully studied, I began my research in 2017.

    Scientific materials for all our research in the spring-summer and autumn seasons of 2017-2022. the following types of water bodies on the coast of the Zarafshan River will be used: reservoirs - Kattakurgan, Tusinsay, Karatepa, Karasuv and Akdarya reservoirs; rivers - Zarafshan, Akdarya and Karadarya reservoirs; canals - Bulurgursky, Dargomsky, Narpaysky, Siebsky, Eskiankhansky and Tuyatortarsky canals and hydrobiont organisms, common in several fish farms, were studied in terms of species composition and ecology.

    As a result of this studied research material, we have so far published articles in 3 national, 3 foreign journals and more than 13 different conferences, in particular in 2 journals listed in the Scopus database.

    Hydrobionts in the territory, like other orangutans, by their importance in nature, occupy an important place in maintaining natural ecological sustainability.

    Leeches are a type of annelids. These are invertebrates that include over 900 species that make up the class Hirudinea. Currently, the number of species of leeches common in freshwater reservoirs is about 500.

    In particular, while most leeches are ectoparasites, the rest participate in biotic relationships in the natural ecosystem in a predator-prey form. Ectoparasitic leeches feed on the blood (hemolymph) of vertebrates (mammals, birds, turtles, amphibians, fish) and invertebrates (mollusks, oligochaetes). Predatory species of leeches feed mainly on insect larvae in aquatic ecosystems, small gastropods and oligochaete worms.

    Using the bioindicator properties of leeches, it is possible to assess the organic pollution of water bodies. This, in turn, is important because it is the biological agent that helps to develop methods that are currently becoming relevant - to prevent the problem of water pollution, to mitigate its negative consequences. In addition, biotopes of populations of leeches parasitizing in the oronasal cavity of animals, the life cycle of which, on the basis of recommendations aimed at their protection, can be used to stabilize the economic effect, indicate compliance with ongoing world studies.

    On the territory of the Middle Zarafshan, only one species of crabs is distributed - Pontastacus leptodactylus, the main biomass of which is concentrated in the Kattakurgan reservoir. The body is on average 11.4-12.3 cm long. The shrimp, scattered throughout the biotopes of the reservoir, hide in their nests during the day, and actively move around and look for food at night. They eat differently, most often they eat carrion, small fish, as well as plants with a high content of calcareous matter. The body is covered with a cuticle made of chitin.

    Shrimp are carnivores, feeding on contaminated fish in water bodies, especially in fish farms, and are of particular importance due to their economic efficiency in fish farms, preventing the spread of disease by acting as natural sanitation.

    Bivalve mollusks living in the territory live in rivers, canals, ponds and at depths of 2–2.5 m in fisheries and reservoirs, most often 0.5–1.5 m, i.e. in well-heated (passed by sunlight) plots. Depending on the aquatic environment in which they live, they are divided into the following ecological groups: Rheophilic - living in wastewater, Peloreophilic - in swamps, Crenophilous - in Springs and pelolimnophiles - living in underwater silts. Bivalve molluscs serve as an indicator in determining water quality.

    The presence and distribution of hydrobionts are greatly influenced by biochemical and geochemical processes. Although the morphophysiological features of hydrobionts, in particular mollusks, in the region of the middle Zarafshan are well studied, the amount of chemical elements in its composition has not yet been studied.

    When determining the need of hydrobiont organisms for chemical elements, it is important to study their composition in the biochemical and geochemical parts. Because with a small or large number of elements in the environment, not only quantitative changes in the internal environment of organisms can occur, but also changes in the external one. Therefore, various diseases arise due to a lack or excess of elements in the body. Studies of the amount of elements contained in molluscs, which play an important role in the bioindication of water quality, are of great scientific and practical importance today.

Sultan Suyarov,

Doctoral student of the Department of Ecology and Life Safety of SamSU.

Scientific adviser - Khusniddin Boymurodov, Doctor of Biological Sciences, Professor.