The results of long-term studies in the cooling reservoir of the Kharanorskaya State District Power Plant (SDPP) (Trans-Baikal Area) are presented, conventionally divided into four periods depending on the increase in its capacity. The stages of phyto- and zooplankton development determined by the influence of technogenic and biotic factors are determined. The response of plankton communities to changes in heat load is shown. Periods of intensive vegetation of algae and mass development of invertebrates alternate with a significant decline in the abundance and biomass of hydrobionts, which indicates an unstable state of the forming cooling pond technoecosystem.

The results of summer studies of phyto- and zooplankton in aquatic systems of technogenic origin are presented. There are low species richness and a significant range of the quantitative indicators of aquatic organisms. The change in the main structure-forming taxa in the pH gradient is shown. Environmental factors that determine the composition and structure of plankton communities have been identified.

The Transbaikalia (Russia) hosts a number of shallow endorheic saline alkaline lakes. The outcome of our studies demonstrated changes in phytoplankton and zooplankton in selected lakes covering a wide salinity gradient (from 0.69 to 128.33 g/L) over a number of years. Our main goal is to assess the variability of structural and functional indicators of phytoplankton and zooplankton communities at the various salinity levels. The gradient of abiotic factors significantly determines the dynamics of planktonic community diversity, abundance, biomass, and production. High values of secondary production was ensured by nonpredators (bacteriovorous, herbivorous, and detrivorus). We found that species and functional diversity of phytoplankton and zooplankton decrease with increasing salinity, whereas their abundance, biomass, and daily secondary production did not. In phytoplankton, a shift occurred from the small-medium cell size unicellular and colonial non-flagellated forms to the large-extra large filamentous cyanobacteria and colonial algae. A shift from selective raptorial and microphagous carnivores to herbivorous copepods and cladocerans and further to more generalist filter-feeder of rotifers and anostracans was observed in zooplankton. These findings are important because they provide a meaningful view of phytoplankton-zooplankton trophic interactions and contribute to an improved understanding their functional effects on aquatic ecosystems. Our results also complement existing knowledge and provides new information about the diversity and functioning of planktonic communities in soda lakes.

The state of the lakes of Southeastern Transbaikalia is assessed. The formation of the hydrochemical and hydrobiological regime of water bodies in the study area occurs under semi-arid climate conditions. The existing cyclical climate fluctuations with a periodicity of 27–35 years cause their sequential filling and drying out. These works were carried out during the transition period between low-water and high-water years. The abiotic environmental factors and chlorophyll a concentrations of various phytoplankton divisions, such as green algae, cryptophytes, diatoms and cyanobacteria, are considered. This work was carried out using a FluoroProbe submersible probe (bbe Moldaenke GmbH, Germany). It was established that the observed fluctuations in the level regime of lakes affect abiotic indicators, causing changes in the content of chlorophyll a of phytoplankton. The principal component analysis showed that the chlorophyll content of green algae depends on the content of potassium and sodium, bicarbonates, and chlorides. The chlorophyll content of cyanobacteria depends on the concentrations of calcium and magnesium. The chlorophyll content of cryptophyte algae depends on the depth of water bodies. Thus, changes in water levels in lakes affect the hydrochemical composition, which determines the structure of phytoplankton communities. Consequently, changes in the abiotic conditions, influencing the development of primary producers, are manifested in changes in the pigment composition of phytoplankton. Currently, most of the studied reservoirs are passing through the stage of mesotrophic level of their development.

The results of a complex hydrochemical and hydrobiological study of salt lakes in the South-Eastern Transbaikalia during the period of moisture change are presented. The studied lakes, according to the geochemical classification, belong to the chloride and soda types. The taxonomic diversity of aquatic biota decreases while the salinity increases and the hydrochemical type of lakes changes from soda oligo-mesohaline (4–16 g/L) to chloride eu-hyperhaline (33–70 g/L) and to soda hyperhaline (128–231 g/L). In soda oligo-mesohaline and chloride lakes the phytoplankton taxonomic composition is similar and is represented by green and diatom algae, as well as cyanobacteria. Submerged aquatic plants are represented by Stuckenia pectinata in soda oligo-mesohaline lakes. Ruppia maritime was found in the Dabasa-Nor chloride lake. In zooplankton and zoobenthos, rotifers and chironomids dominated respectively. Quantitative characteristics of phytoplankton in oligo-mesohaline lakes are lower than in hyperhaline soda and eu-hyperhaline chloride lakes. The phytomass of submerged aquatic plants, on the contrary, is higher in oligo-mesohaline lakes. In the hypersaline soda lake Borzinskoye, zoobenthos and zooplankton organisms are represented by planktonobenthos species, namely Anostrica, with low abundance.

Aquatic ecosystems in arid regions are important and unique habitats for aquatic wildlife and support species biodiversity. Endorheic soda lakes in Central Asia are subject to great fluctuations in its size depending on climatic conditions. Here we present research results covering the last 20 years, including the period from the maximum filling of the Torey lakes (Transbaikalia, Russia) to their aridification and the initial phase of their refilling. Barun-Torey and Zun-Torey lakes are the largest soda lakes in the arid zone with a large water surface area. A unique feature of lakes is the unstable hydrological regime. The reason for the water level change is the periodic filling and drying of lakes due to cyclic climatic changes in humidity and temperature. We aim to determine the response of the plankton communities to environmental change in the Torey lakes over this period. We analysed the interannual variations in phytoplankton and zooplankton species richness, structure and density. We conducted our studies during various phases of the hydrological cycle, including three periods for Zun-Torey Lake (high (1999 and 2003), intermediate (2007, 2011) and low (2014 and 2016) lake levels) and two periods for Barun-Torey (high water level (1999 and 2003) and the initial filling phase (2014, 2016, 2018, 2020, 2021)). Barun-Torey Lake dried up completely in summer 2009 and since 2013 the initial refilling has been observed. Zun-Torey Lake dried up in fall 2017. Changes in water level and water chemistry determined plankton biodiversity transformation. Fluctuations of plankton communities were different for each lake and conformed the phases of the hydrological cycle. We identified four stage changes in plankton associations during the aridification of Zun-Torey Lake, and three stage changes in plankton associations as the water level fell and through the initial refilling phase for Barun-Torey Lake.

This article presents the results of a comprehensive hydrochemical and hydrobiological study of 13 different types of lakes in Transbaikalia conducted in July 2022. Based on factor analysis of hydrochemical and hydrobiological indicators, the lakes were divided into three groups: 1) brackish soda; 2) chloride and sulfate, as well as one salty soda lake, Shvartsivskoe; and 3) brine soda. It has been established that the number of species of different groups of aquatic organisms decreases as the salinity level increases, regardless of the chemical type of water. It has been shown that the dominant composition of primary producers in lakes of different types differs. Two new species of macroalgae for Transbaikalia have been identified (Stigeoclonium flagelliferum Kütz. and Rhizoclonium riparium: (Roth.) Harv.). In the flora of aquatic plants of Baikal Siberia, after more than a 100-year hiatus, Ruppia maritima L is present. The zooplankton of lakes is dominated by halotolerant species. The dominant structure of zoobenthos in brine and salt lakes is dominated by Artemia crustaceans and Ephydridae flies. In deeper brackish lakes, Chironomidae mosquitoes are always the dominant species. Quantitative indicators of phytoplankton and zooplankton communities are characterized by an inverse relationship. With the massive development of cryptophyte algae in brine reservoirs, the abundance and biomass of zooplankton are minimal. No significant fluctuations in the biomass of zoobenthos and phytomass of aquatic plants were detected. In sulfate and chloride lakes, the trophic structure of heterotrophs is represented in zooplankton by a grazing chain, and in zoobenthos by detritivores.

ФГБУН «Институт природных ресурсов

Saline lakes as an extreme type of ecosystems are the object of intensive multidisciplinary research. The few chloride water bodies are unique in their own way and are of great interest to researchers. Their morphometric, hydrological, physical and hedrochemical characteristics are subject to significant changes, which are caused by cyclic climatic fluctuations. These lakes periodic fill and dry up. Most chloride lakes are localized on relatively level surfaces. The depth and area of the lakes vary depending on meteorological conditions. They are fed by surface runoff water and atmospheric precipitation. The surveyed water bodies are part of the Onon-Borzya group of lakes, located in the Onon River valley in the south-eastern Transbaikalia. The region is characterized by a cryoarid climate. Organisms adapted to living in mineral lakes combine wide physiological tolerance to changing salinity with rather strong dependence on other features of the habitat. We aim is to research the diversity of algae and plankton invertebrates in shallow chloride lakes (Gorbunka, Dabasa-Nur, Hilganta). This work presents the results of primary studies conducted in March and July 2021. Plankton samples were collected and processed according to methods generally accepted in hydrobiology. Taxonomic composition, abundance and biomass of planktonic organisms were revealed. The composition of algae and the ratio of the divisions in the plankton of the surveyed chloride water bodies are typical for water bodies with increased salinity, where cyanobacteria and green algae prevail. In zooplankton one species, rotifer Brachionus plicatilis, which is a cosmopolitan, halobiont and typical inhabitant of inland mineral lakes, was found. Quantitative indices varied within a wide range, which is probably connected with hydrochemical indices and different level of filling of lakes.

The results of a study of the biodiversity of hydrobionts in the Ingoda River are presented. In phytoplankton sixty six taxa of algae with a rank below the genus have been identified. The zooplankton contains 21 species. The species composition of the macrophytobenthos includes 5 taxa. In the flora of hydrophytes, 15 plant species have been identified. The zoobenthos contains 40 species. Our researches have been showed that widespread species prevail in the flora and fauna of hydrobionts in the Ingoda River. Two alien species ( Elodea canadensis and Gmelinoides fasciatus ) have been recorded in the Kenon Lake. A very rare East Siberian species of mayfly Acanthametropus nikolskyi has been recorded in the Ingoda River zoobenthos.

Barun-Torey and Zun-Torey lakes are located in the arid steppe zone of the Central (Inner) Asia, Eastern Siberia, Russia. The Torey lakes are characterizes unstable hydrological regime. The water level variation is explained by the periodic filling and drying of the lakes due to cyclical climatic changes in humidity and temperature. We conducted our studies various water level phases of the climatic cycle: from high water level (1999, 2003) to drying out and the initial filling phase (2007, 2011, 2014, 2016, 2018, and 2020). The aim of this paper is to present long-term research results on changes in the plankton biocenoses of the Torey lakes during a climate cycle, the drying and initial filling of basins. Succession of plankton dominant species is in the direction of: diatoms+green algae and rotifers+crustaceans → green algae and crustaceans → green algae+cyanobacteria and crustaceans → no planktonic algae and invertebrates → cyanobacteria+diatoms+green algae and rotifers+cladocerans+copepods.

Reservoirs of anthropogenic genesis are a special component of the technogenic landscape. Their environmental conditions differ from those of natural water bodies. Such differences include a limited catchment area and a low thickness of bottom sediments, as well as high contents of metals, metalloids, and salts. The objects of our research are various lake formations that formed during the development of mineral deposits in the Eastern Transbaikal region. This article describes the chemical composition of the waters and the species diversity and the structure of hydrobiont communities that are different in their formation and purpose of technogenic reservoirs of mining areas. Algae and zooplankton of technogenic water bodies in a region with an arid climate have been studied for the first time. The studied waters have a variety of morphometric and physicochemical characteristics with a wide range of pH values (2.99–8.80), total mineralization (85.9–9065 mg/L), and content of ore and associated elements. According to the chemical composition, the waters are sulphate and bicarbonate-sulphate, with different ratios of magnesium and calcium. The species diversity of the algae and zooplankton of the studied water bodies is low (75 taxa of plankton algae, 8 taxa of macroalgae, and 63 species and subspecies of plankton invertebrates). This is associated with extreme environmental conditions, where species richness is influenced by physicochemical conditions of the habitat. The determining factors for the development of Cryptophyta representatives are micro- and macrocomponent composition and general mineralization, for other groups of phytoplankton (Cyanobacteria, Bacillariophyta, Chrysophyta, Charophyta, Chlorophyta, Euglenophyta, and Dynophyta) it was the content of bicarbonates. Quantitative indicators of zooplankton are positively related to the concentration of ammonium nitrogen (for Crustacea) and negatively to pH (Rotifera).

Small lakes have lower water levels during dry years as was the case in 2000-2020.We sought to show the biodiversity of plant communities at various water levels in Lake Arakhley.Changes in moisture content are reflected in the cyclical variations of the water level in the lake, which decreased approximately 2 m in 2017-2018.These variations affect the biological diversity of the aquatic ecosystems.We present the latest data on the state of the plant communities in this mesotrophic lake located in the drainage basin of Lake Baikal.Lake Arakhley is a freshwater lake with low mineral content and a sodium hydrocarbonate chemical composition.Changes in the nutrient concentration were related to precipitation; inflow volume and organic matter were autochtonous at low water levels.The most diverse groups of phytoplankton found in the lake were Bacillariophyta, Chlorophyta, and Chrysophyta.High biodiversity values indicate the complexity and richness of the lake's phytoplankton community.A prevalence of Lindavia comta was observed when water levels were low and Asterionella formosa dominated in high-water years.The maximum growth depth of lacustrine vegetation decreased from 11.0 m to 4.0 m from 1967 to 2018.Decreasing water levels were accompanied by a reduction in the littoral zone, altering the communities of aquatic plants.The hydrophyte communities were monodominant in the dry years and were represented by Ceratophyllum demersum.The vegetation cover of the lake was more diverse in high-water years and variations in the lake's water content altered the composition of biogenic substances.These changes were reflected in the lake's phytocenosis.

Установлены абиотические границы распространения гидробионтов в соленых, содовых озерах юго-востока Забайкалья.Показано, что в разные климатические фазы экосистемы одних водоемов могут изменяться в пределах одного равновесного состояния, варьируя в рамках определенного диапазона абиогенных и биогенных характеристик, сохраняя неизменным состав первичных продуцентов.В других водоемах изменяется структура первопродуцентов, в связи с чем выделяются два и три альтернативных состояния экосистемы

In 2017, for the purposes of the Pulp and Saw Mill (PSM) “Polyarnaya”, the spillover dam was constructed on the Amazar River, a left tributary of the Amur River. Upon completion of the dam construction, the waters of the river formed a small river reservoir PSM “Polyarnaya”. This work covers findings on components and quantities of the newly formed reservoir at its initial stage and the data on biodiversity of its feeding flows. At this stage, the species composition of the flora and fauna in the reservoir falls in between the lacustrine and the riverine ones. The riverine conditions are observed in the upstream area of the reservoir; the middle area bears an intermediate status; while the limnetic zone near the dam features transformation of the river system into a lake-like running-water ecosystem. Seasonally, in the period from spring to autumn, phytoplankton showed a decreasing trend of the quantitative values; whereas the total abundance and biomass of zooplankton were increasing; zoobenthos featured lack of trends; macrophytes contents were different from season to season being abundant in the Amazar River near the urban settlement in spring and in the Amazar River downstream from the dam in autumn. Consequently, the initial stage of the formation of the reservoir is rather similar to original watercourses in the physical and chemical parameters and in the composition of flora and fauna as well.

We described the taxonomic structure of planktonic associations in the water bodies of Kharanor State District Power Plant (cooling pond, water supply, drainage, and water intake channels of Kharanor reservoir located in the arid zone of the south-eastern Transbaikalia in a highly continental climate). Hydrobiological researches were conducted in April, July, and October 2019. We identified 141 algal taxa ranked below the genus, representing the divisions of Cyanobacteria (15 taxa), Bacillariophyta (41), Chrysophyta (10), Cryptophyta (3), Dinophyta (4), Charophyta (8), Chlorophyta (56), and Euglenophyta (4), and 52 zooplankton taxa, including 28 species and subspecies of Rotifera, 15 species of Cladocera, and 9 species of Copepoda. In the cooling reservoir, the plankton community included 135 phytoplankton taxa and 38 zooplankton species; 58 algal taxa and 27 invertebrate species were sampled in the water supply channel, 50 taxa and 26 species were sampled in the drainage channel, and 94 taxa and 24 species were collected from water intake channel respectively. Six diatom species (Stephanodiscus hantzschii, Nitzschia sigmoidea, Fragilaria radians, Asterionella formosa, Ulnaria ulna) and four zooplankton species (rotifers Asplanchna priodonta and crustaceans Daphnia galeata, Bosmina longirostris, Thermocyclops crassus) occurred in all water bodies during the entire study period.

Small lakes have lower water levels during dry years as was the case in 2000-2020.We sought to show the biodiversity of plant communities at various water levels in Lake Arakhley.Changes in moisture content are reflected in the cyclical variations of the water level in the lake, which decreased approximately 2 m in 2017-2018.These variations affect the biological diversity of the aquatic ecosystems.We present the latest data on the state of the plant communities in this mesotrophic lake located in the drainage basin of Lake Baikal.Lake Arakhley is a freshwater lake with low mineral content and a sodium hydrocarbonate chemical composition.Changes in the nutrient concentration were related to precipitation; inflow volume and organic matter were autochtonous at low water levels.The most diverse groups of phytoplankton found in the lake were Bacillariophyta, Chlorophyta, and Chrysophyta.High biodiversity values indicate the complexity and richness of the lake's phytoplankton community.A prevalence of Lindavia comta was observed when water levels were low and Asterionella formosa dominated in high-water years.The maximum growth depth of lacustrine vegetation decreased from 11.0 m to 4.0 m from 1967 to 2018.Decreasing water levels were accompanied by a reduction in the littoral zone, altering the communities of aquatic plants.The hydrophyte communities were monodominant in the dry years and were represented by Ceratophyllum demersum.The vegetation cover of the lake was more diverse in high-water years and variations in the lake's water content altered the composition of biogenic substances.These changes were reflected in the lake's phytocenosis.

Waterbodies with a naturally high level of mineralization are geographically widespread. They are found not only in hot and arid regions but also in some regions with temperate and cold climates, in particular, Eastern Siberia. Usually, these are groups of closed lakes that share common features: their location in a semiarid climate zone, the absence of surface runoff, a shallow depth, and a limited catchment area. They have significant variations in size and mineralization. The article presents the results of studies of the structure of plankton communities and the relationship between environmental factors and the main characteristics of plankton in littoral biotopes of different types (overgrown and open littoral) of soda lakes of the Onon–Borzin system.

The present paper is based on the results of long-term studies of planktonic algae and invertebrates in the fresh, soda and saline and technogenically loaded water bodies. The priority abiotic factors (hydrochemical composition, hydrophysical parameters), determining the development (species number, dominant species, abundance and biomass) of the main taxonomic groups of phyto- and zooplankton were determined.