Search

In 2017, a spillover dam was constructed in the middle course of the Amazar River of Russia, forming a reservoir to provide water to the Amazar Pulp and Saw Mill project known as Polyarnaya. The dam uses an integrated approach, combining hydrochemical, hydrobiological, and ichthyological methods, as well as echo sounding. Comprehensive studies of the transformation of the Amazar River into a reservoir demonstrate the initially low biodiversity of hydrobionts characteristics for a semi-mountain river under the conditions of the sharply continental climate of the Trans-Baikal region. During the initial stage of formation, the reservoir was similar to the original watercourses in physical and chemical parameters and in the composition of the flora and fauna. It featured extensive shoals that were gradually turning into silt-covered and plant-filled shallow bays. These bays will eventually be locations of maximum concentration and diversity of hydrobionts and future nursery and spawning grounds for fish. The construction of the dam has significantly changed the hydrology of the Amazar River downstream of the dam. These findings reveal problems related to fish migration to the Thymallidae and Salmonidae spawning areas, as well as reductions in the biodiversity and quantity of the macrozoobenthos typical for run-of-river reservoirs.

The ecosystem of water bodies and their general organic productivity are determined by the composition of phytoplankton and its photosynthetic activity. The qualitative and quantitative composition and the ratio of phytoplankton pigments in the Kharanor reservoir were studied according to the data of field studies during the ice-free period. The dominant complex of phytoplankton, represented by 16 species from 6 divisions, was revealed. In the formation of the total biomass, the leading role belonged to green, diatoms and golden algae. The obtained values of the indices of biodiversity, equalization and dominance for the reservoir indicate the simplification of the structure and average biodiversity of the phytoplankton community as well as the monodominance of the phytoplankton complex. The heterogeneity of the biotopic characteristics of different parts of the reservoir is manifested in the variability of the values of green pigments. In the area of the discharge channel of the hydroelectric power station, the ecosystem is under constant influence of the temperature factor. The increase in the content of chlorophyll-a in the area of the pumping station is associated with the intense mixing of water masses when pumping water from the Onon River. The constant mixing of river and lake waters in the reservoir does not contribute to the stabilization of the ecosystem, as indicated by the predominance of carotenoids over green pigments, positive indicators of pheophytin and the ratio of carotenoids/chlorophylls. The values of the pigment index indicate the physiological activity of phytoplankton in the production of organic matter. In general, the ecosystem retains its mesotrophic level of development.