Vol 17, No 3 (2024)

The results of long-term studies in the cooling reservoir of the Kharanorskaya SDPP (Transbaikalia) are presented, conventionally divided into four periods depending on the increase in power plant 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 number and biomass of hydrobionts, which indicates an unstable state of the forming cooling pond technoecosystem.

According to data of 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), and Najas major (3), 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 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 the Najadaceae species since the beginning of the 21st century, both in 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.

The variability of the morphological characters of the genus Alburnoides Jeitteles, 1861 from watercourses in the south of Russia (five rivers of the Crimean Peninsula and two rivers of the Krasnodar Territory) is considered. It has been established that in spirlins within the study areas, body sizes average from 60.1 ± 1.45 mm in individuals from the river Gostagayka (Krasnodar region) up to 88.2 ± 1.87 mm in fish from the river Angara (Crimean Peninsula). Using the Mann–Whitney test, statistically significant differences were registered between the samples in most plastic characters; they were absent in meristic characters. In the studied regions, heterogeneity in the structure of the genus Alburnoides was noted: according to the results of cluster analysis for the totality of all studied characters, the greatest similarity was found in samples from Crimean rivers that are geographically close to each other (rivers Chernaya, Belbek, Kacha and Alma), but group from the river Angara adjoins them at a higher level of divergence. A separate group is formed by samples from the rivers of the Krasnodar Territory. The obtained data are consistent with the literary information on the formation of the ichthyofauna in the rivers of Crimea; the established clear differences between the charaters from the rivers of southern Russia require a more detailed study.

The results of an ecological and anatomical study of plants in the coastal shallows of rivers and lakes o the Lower Amur region are presented in order to identify their resistance and adaptability to the conditions of existence. 7 stenotopic species were studied. It was revealed that the vegetative organs of plants are characterized by a combination of typical hydromorphic and specific adaptive features. Adaptation of species to sandy-silty shallow habitats is carried out due to histological transformations of the main tissues. The narrow specialization of species does not affect the typical structure of plant organs and does not lead to a simplification of their internal structure. The studied species are more characterized by signs of terrestrial micromorphology (sclerification, suberinization and cutinization of tissues) rather than hydrophytic. It is assumed that a specific complex of shallow flora was formed mainly from terrestrial species.

Using the example of the rivers of the Onega Lake basin, the species composition of mollusks of the Sphaeriidae family, their abundance, biomass, and contribution to benthic communities in rivers with many lakes in the catchment areas were analyzed. Patterns of spatial distribution of species across biotopes and gradients of environmental variables were traced. 26 species of mollusks of this family were identified, among them European-Siberian species predominate. Most of the species of mollusks of the family Sphaeriidae found by us have wide ecological ranges and are found in water bodies of various types. It was found that the contribution of Sphaeriidae to the species richness and functioning of aquatic communities in rivers in the conditions of branched lake-river systems (Lake Onega basin) exceeds the values usual for rivers with a small number of lakes in the catchment area. Using the ANOSIM and PERMANOVA methods, it was proved that the species composition of rocky rapids and riffles, sandy rifts and soft bottom soils is different. Using the IndVal test, seven species were shown to have a statistically significant association with one of these biotopes, and four of them, with rocky bottoms of river rapids and riffles. Using the NMDS method, it was shown that the greatest changes in the species composition of representatives of Sphaeriidae are observed when environmental conditions change from small streams with slow current and brown water to large rivers with fast current and clear water.

A study of changes in sea surface temperature (SST) on the South-Western shelf of the Crimea in 2000–2020 was conducted. The equations of trends in the change of SST are found. It is shown that according to the nature of changes in the average annual sea temperature, three periods can be divided: 2000–2007, 2008–2013 and 2014–2020. The influence of changes in the average annual SST on the development of pelagic fish of the cold-waters complex (on the example of the Black Sea sprat) is considered. Changes in the main parameters of populations and their relationship with the change in the average annual SST were found. It was found that the observed increase in sea temperature negatively affected the development of the sprat population, the average age of the population decreased by 1.3 times, in general, the population was rejuvenated, the average size and weight of individuals decreased.

Studies of the pollution of Lake Baikal with microplastic particles have been started quite recently. Almost all research is focused on the assessment of surface water pollution, while the impact of microplastics on Baikal organisms remains unexplored. We conducted a laboratory experiment involving three species of gastropod mollusks, the Palearctic Lymnaea stagnalis (L., 1758) and Radix auricularia (L., 1758), as well as the Baikal endemic Benedictia baicalensis (Gerstfeldt, 1859). Two types of microplastics were used in the experiment: fragments of polystyrene and polyester fibers, prepared independently in the laboratory. These plastic particles, along with the food mixture, were placed in aquariums with mollusks. In total, as a result of the experiment, 386 preparations with mollusk excrement were obtained, of which 144 preparations were for the Radix auricularia species, 176 for the Lymnaea stagnalis species, and 67 for the Benedictia baicalensis species, the experiment with the latter species was carried out only with microplastic fragments. All preparations were analyzed according to the degree of fluorescence. The data were statistically processed using Spearman’s rank correlation coefficient. The data obtained allowed us to conclude that gastropods of these species are able to absorb microplastic particles and remove them from the body. However, the rate of removal of microplastic particles from the body of a mollusk is species-specific, and also directly depends on the morphological structure of microplastic particles.

A study of the accumulation of radionuclides ⁹⁰Sr, ¹³⁴Cs, ¹³⁷Cs by a lake frog (Pelophylax ridibundus Pall., 1771) living in the areas of the reservoirs of the Middle Urals was carried out. The variability of size and mass indicators and concentrations of radionuclides in animals in the surveyed area was noted. Increased concentrations of ¹³⁷Cs and ¹³⁴Cs were detected in some amphibian representatives compared to the average values. A significant decrease in the concentration of ⁹⁰Sr in frogs with an increase in raw body weight was found on a large statistical material. Analysis of the data obtained on the concentrations of ⁹⁰Sr and ¹³⁷Cs in frogs of different sexes did not reveal a significant difference in the accumulation of both radionuclides between male and female animals, as well as in the accumulation of ⁹⁰Sr by striata and strieless amphibians. It is shown that radionuclides ⁹⁰Sr and ¹³⁷Cs enter the animal body from water much more than from the ground, while with an increase in the concentration of radionuclide in the habitat, the coefficients of their transition into the animal body decrease.

The article describes the scientific and methodological possibilities of bioassay in the field of studying the effects of climate change on water bodies and aquatic organisms. In fish aquaculture, it was revealed that an increase in water temperature changes the biochemical parameters of the internal environments of organisms, affects their behavior and the number of offspring. A number of biogeochemical transformations of aquatic ecosystems are predicted: a decrease in the pH of water, mineralization of organic matter of bottom sediments, release and increase in bioavailability of compounds of potentially toxic elements. Bioassay methods using monocultures and laboratory microcosms have shown that maximum temperature values and a cascade of concomitant changes will lead to a restructuring of the aquatic life community, changes in the habitats of organisms, and the disappearance of stenothermic species. The realism of such scenarios is confirmed by paleodata and modern natural phenomena.

The study of algological material from tundra lakes of the adjacent territories of the Ust-Lena Reserve (Yakutia) using scanning electron microscopy revealed a new species of diatoms for science Buryatia strelnikovae sp. nov. The new species has morphological similarities with other species of the genus B. oviformis and B. crassa. It differs from the former by large values of the number of striae and areolae of 10 µm, from the latter by smaller length and width of the sash and large values of the number of strokes and areoles of 10 µm, but differs from them in smaller leaf length and width, large values of the number of striae and areolae of 10 µm.

The data on the discovery of the cornucopia of the narrowed Typha angustata in the delta of the Don River are given. In the “Flora of the USSR” this species was understood quite broadly, its range stretched from the Danube to the Pacific Ocean. For a long time, it was not found and was referred to as synonymous with T. australis, T. domingensis T. angustifolia. The species has not disappeared from the composition of the hydrophilic flora of Russia. It is preserved in the “arms” of the Delta of the Don River. As a result of isolations in the Cenozoic, which led to the severance links with the eastern and western water basins, the range was significantly reduced and the rate of evolution was reduced. In the modern geological period, T. angustata is undergoing natural elimination.