Известия высших учебных заведений. Поволжский регион: Естественные науки (Mar 2021)
Zooplankton communities in the new and old Sura riverbeds in Penza
Abstract
Background. The Sura River in Penza and its vicinity undergo significant natural and anthropogenic (dam construction) impacts in 1942–1943, which caused a change in the riverbed. In the course of its natural meandering a channel was formed, which has became the main in 1945 after the breakthrough of water through the hydroconstruction, and the old Sura turned into the former riverbed. In 1970, after the creation of the Penza reservoir above the city, the state of the watercourse and adjacent reservoirs, as well as the hydrobionts inhabiting them, changed even more. The river regime is also affected by the reservoir created in 1959 at Heat Electropower Station-1. Over the past 75 years, aquatic ecosystems have been formed, the similarities and differences of which can be studied on the example of zooplankton communities that respond quickly to changes in the environment. The aim of the work is to study zooplankton communities in the new and old riverbeds of the Sura River, as well as to identify key factors and their possible influence on the formation of the structure of these communities. Materials and methods. Material for the study consists of zooplankton samples taken in the modern channel of the Sura river 7 stations: in village Zasechnoe of (I) to the confluence (IIа) and after the confluence (IIb) of the Moyka river, to the confluence (IIIa) and after the confluence (IIIb), Kashaevka river, behind the dam of Heat Electropower Station-1 (IV), after sewage treatment plant (V), and in the old riverbed at 8 stations: flow Barkovki (PB1 and PB2), sedimentation tank (O), oxbow lake Altаrca (A1, A2), in the Akhuny microdistrict in the Staraya Sura river (SS) and two oxbow lakes: Kalashny Zaton (KZ) and the Podkovka oxbow (SSP). In total, 55 samples were processed according to generally accepted methods, which were taken monthly in the spring-summer period of 2020. The physicochemical parameters of the environment were analyzed in August. Results. Totally 82 species have been found in zooplankton communities. The highest number of species was recorded at one of the stations of the modern Sura riverbed Sura, and the lowest – in the Staritsa watercourses. According to structural parameters (population, number of species, their occurrence, proportion of dominant species), the zooplankton communities of the Sura River at stations near the Heat Electropower Station- 1 dam are significantly different compared to other sampling points on the river. The reason is due to the transformation of the watercourse in this area into a reservoir, i.e. with a significant decrease in the flow of the river due to the construction of the dam. The pH of water and the content of such components as NO2–, NO3–, SO4 2–, Ca2+, BOC5, suspended substances and water hardness are lower than in the new riverbed in August at stations of different types of water bodies in the old riverbed of the Sura River. The highest values of these parameters in the Sura River at stations IV, V are due to the accumulation of pollutants entering the watercourse within the city and directly at their locations. The dependences of the abundance of 11 of the 18 dominant species on 19 environmental parameters were statistically significant. Parameters of the indicator species number and structural parameters of zooplankton communities indicate the contamination of the studied water bodies and characterize them as mesotrophic and eutrophic. Conclusions. Differences in zooplankton communities of the new and old Sura River beds are due to different regimes (flow rate, overgrowth, etc.) and anthropogenic impact. In the old riverbed, as well as at the last station of the Sura River, due to the slow flow and accumulation of organic substances as a result of the death of vascular vegetation, numerous algae, as well as the arrival of organic matter, zooplankton communities indicate the transition of water bodies from mesotrophic to eutrophic type.
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