Biologiâ vnutrennih vod

In the summer of 2015–2023, pigments in bottom sediments were studied as indicators of the trophic state of benthal in the large channel Saratov Reservoir, which stands out in the cascade of Volga River reservoirs for high rates of water exchange and sedimentation. In the reservoir, the areas of coarse-grained sediments exceed those of fine-grained sediments by 4.2 times. Average content of chlorophyllawith pheopigments in the upper 5-cm sediment layer (12.4 ± 1.6μg/g dry sediments), calculated considering the areas of bottom sediments of different types, corresponds to the oligotrophic category. The most common values of pigment concentrations vary within the oligotrophic and mesotrophic categories. Concentrations of organic matter and pigments per 1 g of organic matter of bottom sediments in the Saratov Reservoir were minimal for the Volga cascade.

This scanning electron microscopy study revealed 297 species and varieties of diatoms from 72 genera in the phytoperiphyton of the Svir River tributaries, which allowed us to obtain the first data on the species composition of Bacillariophyta in a number of tributaries of this watercourse (Yanega, Uslanka, Vazhinka, Ivina) and expand it for Oyat and Pasha. Among them, 15 species are new to the flora of Russia and 59 forms from 19 genera were identified only up to the genus rank. The greatest species richness was recorded in the Yanega (118) and Ivina (148) tributaries and the highest taxonomic richness was observed among the genera Nitzschia (25), Navicula (26) and Sellaphora (34). A similar number of species and varieties, 208 and 219, respectively, were detected in the left-bank and right-bank tributaries.

Artemiapopulations from seven hyperhaline lakes of Altai Krai (Bolshoye Shklo, Bolshoye Yarovoye, Kulundinskoye, Kuchukskoye, Maloye Shklo, and Tanatar III) were studied. DNA barcoding of these populations allowed identifying two species ofArtemia:A. parthenogeneticaBarigozzi, 1974 andArtemiasp. Information on morphological and biometric features of adult individuals, as well as peculiarities of their habitat is given. Most of the analyzed morphological traits in the studied populations showed great variability, which is probably due to the influence of environmental factors (including water salinity) on them. At the same time, a morphometric index (minimum length of bristles on the furcae) was revealed, in terms of which the studied populations of these two species differ reliably.

The current state of the semi-aquatic mammalian complex of the Vyatka River floodplain under conditions of state protection (in the Nurgush State Nature Reserve and its buffer zone in the Kirov oblast) has been studied: the species composition, the population trend, their distribution over the territory, the environmental impact. The census was taken according to a generally accepted method with covered about 50% of the studied territory. It is shown that the Nurgush State Nature Reserve has restored and protected a full complex of semi-aquatic mammals typical of the European southern Boreal floodplain (7 species). The number of beaver has reached the capacity of habitats and fluctuates slightly around its size. The muskrat introduced in the study area has an extremely low population for the last decade; therefore, the species does not play any role in ecosystems. The native European mink was completely replaced by the introduced American mink, which has occupied the ecological niche of the displaced species. The otter under conditions of state protection from 2005 to 2024 has turned from a critically low-numbered species into a common one. The otter population recovery seems a limiting factor for the muskrat. The Russian desman has been recognized as a species with an extremely low density in the Nurgush State Nature Reserve; the probable population size in the Reserve and its buffer zone is up to 10 individuals. The Eurasian water shrew is a stable component of the mammalian complex of the studied area. Due to the low numbers, this species has no environmental significance. The European water vole was not numerous during the period of our research, which does not allow us to fully assess its importance in the communities.

The study resultsof thealgicidal activity of the MK17 metabolites crude isolated from the soil actinobacteriumStreptomyces flavogriseusMK17 biomass are presented in this paper. The mechanisms of metabolites MK17 stress effect on cyanobacteria were investigated. MK17 metabolites exhibit algicidal activity against cyanobacteria and green algae, with cyanobacteria being more sensitive to their effects than green algae. It was revealed that under the effect of MK17 metabolites crude there is a decrease in the concentrations of microcystins formed by toxigenic cyanobacteriaMicrocystis aeruginosaandPlanktothrix agardhiiin the medium. It is shown that MK17 metabolites cause damage to the functions of the cyanobacterial photosystem. Increased generation of active oxygen species in cells and, as a result, an increase in the content of malonic dialdehyde and activation of antioxidant defense mechanisms indicate the development of oxidative stress in cyanobacterial cells under the MK17 metabolites effect.

A clonal culture of the coccolithophoreEmiliania huxleyiwas isolated from the plankton of the Black Sea in February 2023. Its species identification was carried out using scanning electron microscopy and it was established that it belongs to type A. The optimal temperature for the development of this culture was revealed to be 20°C. The temperature coefficient (Q10) for the temperature range of 5–15°C was 3.36, and for the range of 10–20°C it was equal to 2.75. The influence of light on the structural and functional parameters of this species was studied. The maximum specific growth rate (1.37 day^-1) was achieved at a light intensity of 157 µE/(m² × s), and then it decreased as a result of light inhibition. The relative content of chlorophyllaper cell and dry weight decreased by 3–5 times as the light intensified from 8.5 to 425 μE/(m² × s). The transfer ofE. huxleyicells, which have the maximum intracellular pool of nutrients, into seawater depleted in nutrients, caused a decrease in the increase in their number and the efficiency of photosystem II, as well as an increase in cell volume and surface area. The sensitivity of photosystem II to phosphorus deficiency was higher than to nitrogen deficiency. Due to the intracellular pool of nutrients, this type of algae carried out 1.43–1.77 cell divisions.

The possibility of introducing the speciesTrapa natansL. to Saratov Region was studied. Donor material from the lower Volga (Astrakhan Region), the Middle Don (Volgograd Region) and the Khopyor middle reaches (Voronezh Region) reservoirs was used. The fruits weresown within the boundaries of the Saratov Region in 77 places in the floodplains of the Khopyor, Medveditsa, Tereshka and Volga rivers. For morphometric analysis, 16 morphometric parameters were measured in 30 rosettes from each population. The ordination of the points was performed using the Principal Component Analysis (PCA). The Medveditsa and Tereshka rivers turned out to be unsuitable for the existence of reintroduced populations. The reintroduction ofT. natansto the floodplain of the river was successful. The reintroduction of the species into the Khopyor and Volga rivers was carried out using donor material from the floodplains of the Don River (Volgograd Region) and the Khopyor River (Voronezh Region). The material from the Astrakhan Region, on the contrary, is unacceptable as donor material for reintroduction into Saratov Region. According to morphological features, natural populations from the Voronezh Region are more variable than populations from the Astrakhan Region. The population from the Astrakhan Region is characterized by larger rosettes and leaves than populations from Voronezh Region. In the reintroduction populations created in the floodplain of the Khopyor River within the Saratov Region, the leaf and rosette parameters were higher, and the fruit productivity was lower than in the donor populations from Voronezh Region. At the same time, in the reintroduction populations of first vegetation year, compared with the donor populations, a range narrowing of morphological and productive variability of individuals was observed.

The seasonal dynamics of zooplankton (Rotifera, Cladocera, Copepoda) were studied in the Ob River in years of different water levels in the zone of influence of the Novosibirsk Hydroelectric Power Station and in the middle reaches of the Ob River. Zooplankton samples were collected and analyzed using standard methods. Research has shown that the middle reaches of the Ob River are characterized by the formation of two summer peaks in zooplankton abundance and the presence of a clean water phase in late June – early July at the decline of the second flood wave and at the very beginning of the summer low-water period. In the section of the Ob River below the hydroelectric dam, the summer peak of zooplankton development is “cut off” due to the design features of water intake to turbines and the features of discharge regulation. In both sections of the river in the same season in different years, the number of zooplankton species, as well as the abundance and biomass of zooplankton, can vary significantly. Seasonal changes in the numerical indicators and species structure of the zooplankton community depend on the synergy of biotic and abiotic factors. During the flood period, the leading role in the formation of the zooplankton structure is played by the hydrological parameters of the watercourse, and during the summer low-water period – the water temperature. The spring and summer peaks in zooplankton abundance are mainly provided by rotifers, but the species composition varies significantly. The spring peak, as a rule, is ensured by the massive development of representatives of the genusKeratellaandSynchaeta, and in July-August the species of the river dominate in numbers genusBrachionusandPolyarthra. The change of taxa is determined by the biological characteristics of species. In both studied areas, regardless of the quantitative indicators of zooplankton, maximum values of the Shannon index were revealed in August.

The study was conducted on the feeding selectivity of larvae of pikeperchSander lucioperca(Linnaeus, 1758) in early ontogenesis (from 3 to 21 days after hatching) under culture conditions when feeding zooplankton from Lake Sukhodolskoye, the natural habitat of pikeperch. The basis of pikeperch larvae feeding during the first 15 days was the cladoceransBosmina longirostris(O.F. Müller, 1776) andPolyphemus pediculus(Linnaeus, 1758) (up to 80–100% of food items in the food bolus) – the most common species in the lake (92.92–99.57% of the number of zooplankters). At the initial stages of the life of pikeperch larvae, the proportion of food items available in size for their feeding reached 8.7%. The proportion of zooplankters favored by larvae for feeding was also low (18%). This appeared to have a negative impact on juvenile survival (~30% in the first week and 3.6% at the end of the study), as well as significant variability in larval size (coefficient of variation in juvenile mass 72%) and cannibalism.

The content of Cu, Zn, Pb, Cd, Ni and Fe, as well as the percentage of nauplii hatching from cysts, were studied in Artemiacysts collected in the Western Basin of the Saki Salt Lake in different seasons of 2017. The content of Cu varied within 5.58–13.48 mg/kg, Zn 38.34–53.04 mg/kg, Pb 0.69–2.94 mg/kg, Ni 1.17–5.73 mg/kg and Fe 223.6–321.5 mg/kg. The highest content of metals in cysts was noted in December, the lowest in June and October. High values of the correlation coefficient (more than 50%) were found between the content of Cu, Cd, Pb and Ni, as well as between the content of Cd, Pb and Ni. The lowest values of % hatching of nauplii from cysts were noted in June, and the highest ones – in December. There is no significant correlation between the content of metals in cysts and % hatching of nauplii from them. Various reasons for the fluctuation of metal content in Artemiacysts are discussed, which include precipitation, flood waters, runoff from agricultural lands, temperature fluctuations and other processes.

Based on the well-known factof the short-term metamorphosis of amphibiotic insects when emerging out directly from the water bodies’ surface, the author proposes a calculation method for such departure rate estimating from lotic systems based on drift collections. The calculation is made taking into account the area of the bottom site (1 m²) adjacent to the observation section. In passing, the problem of the discrepancy between the efforts spent on data collecting and the meager volume of data obtained is considered, which is especially relevant when working on small watercourses, where the emergence of some species is scattered and low-intensity.

A new finding of the diatomStephanodiscus hantzschiiGrunow, 1880 in Khalaktyrskoye Lake (Kamchatka) during the period of its mass growth in April 2023 is described. Density of this species was 4.95 million cells/l or 92.6% of the total density. A list of 45 species of associated diatoms is provided. According to electron microscopy data, it was established that the population ofS .hantzschiiwas represented by two morphotypes –hantzschiiandtenius, differing in quantitative (number of areolae and rows of areolae in 10 μm) and qualitative (shape of spines, location and shape of areolae on the valve face) characteristics. Features in the shape of the areolae and their location for different frustules of thehantzschiimorphotype have also been identified. Mass growth of this species and noted morphological features of its frustule structure could be due to the high level of eutrophication of the Khalaktyrskoye Lake.

The results of the experiment showed that the development of Cyclops insignis Claus, 1857 (Copepoda, Crustacea) embryos irradiated with γ-radiation doses of 50 and 100 Gy at the 1, 2 and 4 cell stage occurs up to the 4–16 cell stage. It is assumed that high doses of radiation lead to inactivation of the nuclear genome, and the development of embryos up to the 8–16 cell stage occurs due to cytoplasmic determinants.

In the spring of 2024, in the Middle Caspian off the coast of the Republic of Dagestan from Makhachkala to Kaspiysk, a massive development of the population of the copepodCalanipeda aquaedulciswas discovered, which was absent here for almost 20 years. It again entered the group of dominant species and formed an average of 92% of the total biomass of zooplankton. Mature males (45% of the total number), females (47%) and immature crustaceans of copepodite stages of development (8%) were recorded in the population. In the early 2000s,C. aquaedulciswas badly damaged by the introduction of the copepod Acartia tonsa and the ctenophore Mnemiopsis leidyi into the reservoir. Currently, there is hope for the restoration of theC. aquaedulcispopulation in the Middle Caspian.