As a result of comprehensive studies in Arbakalir Lake and Charskii Hot Spring during the growing season in 2021, the physical and chemical parameters of water and the species and phytocenotic diversity of vegetation were studied. In the flora of water bodies, 56 taxa from seven divisions, of which 31 species belong to flowering plants, 22 species to macroalgae, and one species in each to bryophytes, horsetails, and lycophytes were identified. Two species are included in the Red Book, at both the federal and regional levels. Two species are classified as relict. The structure of the flora contains species of three ecotypes, of which 38 species (67.9

Lake Gusinoye is the largest lake in the Baikal natural territory after Lake. Baikal, around which the Gusnoozersky industrial complex is formed. In the macrophyte flora of the lake. 27 species from 21 families have been identified. The spatial structure of vegetation is determined by the morphometric characteristics of the lake's littoral zone. The northern and southern sectors of the lake are the most overgrown. Compared to previous years of research, an increase in the area of charophyte and moss thickets was revealed. The progressive overgrowing of the lake helps to maintain the processes of self-purification of the ecosystem, removes pollutants and nutrients from circulation and ensures the sustainable development of the ecosystem. The ability of the lake ecosystem to maintain the overall level of productivity due to restructuring of the structure is also evidenced by data on other communities of hydrobionts (zooplankton, zoobenthos and ichthyocenoses). The results of our studies of the chemical composition of macrophytes of Lake. Gusinoe showed, in comparison with the data of the 90s, the concentrations of chemical elements in macrophytes decreased. The recorded ecological state of the lake is determined by a complex of factors, both natural and natural (water level, temperature rise, littoral morphometry, chemical composition of water).

According to data on the late 20th century in the Trans-Baikal and Baikal areas, the family Najadaceae is represented by four species known in few localities: Caulinia flexilis (4 localities), C. minor (3), Najas major (3), and N. marina (4). All of them are annuals, r-strategists, which are characterized by fluctuations in abundance. Since the 21st century, these species have been found in 20 more localities, mainly situated within the Baikal Depression. In 2015, when performing monitoring studies of aquatic flora, three more new localities of Caulinia flexilis, C. minor, and Najas major were found in the basin of the Amur River. Distribution maps of the Najadaceae species in the region were compiled, and the ecological characteristics of their habitats were given. In Trans-Baikal area, since the middle of the 20th century, warming has occurred due to an increase in the average annual temperature. For the last 70 years, aridization has increased in southern regions, which changes the habitat conditions in waterbodies. Findings of these Najadaceae species in Trans-Baikal area have coincided with the periods of increase in mean annual air temperatures and with local minimums of precipitation. An increase in the number of findings of Najadaceae species since the beginning of the 21st century, both in the Trans-Baikal area and in other regions of Russia, has been occurring against the background of an increase in the average annual air temperature. In Trans-Baikal area, the trend of increasing of temperatures in the warm season since the beginning of the 21st century is favorable for these species and may contribute to their further distribution.

As a result of comprehensive researches in the Lake Arbakalir and the Spring Charsky Goryachi klyuch during the growing season in 2021, the physical and chemical parameters of water, species and phytocenotic diversity of vegetation were studied. 56 taxa from 7 divisions of which 31 species belong to flowering plants, 22 species to macroalgae, one species in each to bryophytes, horsetails and lycophytes were identified in the flora of water bodies. Two species are included in the Red Book, both at the federal and regional levels. Two species are classified as relict. The structure of the flora contains species of three ecotypes, of which 38 species (67.9 %) belong to true aquatic plants. 18 associations from 12 formations were identified in the syntaxonomic structure of aquatic and coastal aquatic vegetation. Based on factor analysis, the main factors influencing the distribution of phytocenoses are water temperature, pH, mineralization, and main cation, anion and nutrient contents.

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.

ДИНАМИКА БИОМАССЫ И ПЛОЩАДИ ЗАРАС-ТАНИЯ ВОДНОЙ РАСТИТЕЛЬНОСТИ ОЗЕРА КЕНОН (

Приводятся сведения о находках реликтового вида Ruppia maritima в соленых озерах Восточного Забайкалья России (Забайкальский край) и северо-востока Монголии. Дана информация о количественных показателях популяций, экологических условиях, минерализации и pH озерной воды.

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.

. Information is given about the finds of the relict species Ruppia maritima in salt lakes in the southeast of Transbaikalia of Russia (Trans-Baikal Territory) and in the northeast of Mongolia. Information is present on quantita-tive indicators of populations, ecological conditions, salinity and pH of lake water.

Previously, a hypothesis was put forward about a change in the degree of hydrophicity of lakes under the influence of fluctuations in the level. At the same time, the direct abiotic factors leading to ecosystem changes are the illumination of the soil and the level of its wind resuspending. At the same time, there were no empirical correlations between these indicators in relation to the lakes of the Ivano-Arachley system. In this work, based on the study of the lakes of the Ivano-Arakhley system, during the period of extremely low water content, a correlation is shown between the depth of macrophyte growth and the transparency of water at a damage of 0.96 (p=0.002). Factor analysis by the method of principal components showed a high positive relationship with the morphometric parameters of the ecosystem and the degree of openness of the reservoir. The relationship between the depth of vegetation distribution, water transparency, the ratio of depth, lake area expressed in terms of the coefficient of openness must be taken into account when planning activities on lakes that can affect vegetation or water transparency.

The paper presents the results of studying of the aquatic vegetation of Lake Kenon based on the integrated use of traditional methods of visual survey with an echo sounding. The use of echo sounding surveys makes it possible to study better the features of the distribution of submerged aquatic plants. It allows you to speed up the process of sampling in the field, and also facilitates office processing of the received data. Based on the measurement results, a bathymetric map was built, and the boundaries and areas of dominant phytocenoses were determined. It was revealed that at present the total area of thickets is 489 hectares, which is 33 % of the lake area. The maximum depth of plant growth was 5.1 m. The data obtained is higher than the percentage of overgrowth in 1993, but lower than the values for the 70s and 80s. At present, as in previous years, Chara algae are leading in terms of overgrowing area. The decrease in the distribution area of Nitella flexilis and Potamogeton crispus was revealed.

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 ofLindavia comtawas observed when water levels were low andAsterionella formosadominated 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 byCeratophyllum 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.

О современном состоянии и многолетней динамике флоры и растительности озера Гусиное (Республика Бурятия)Базарова Б. Б

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

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.

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.