CONTENT
Environmental Concerns and the State of Aquatic Environment
Hydrochemical regime and contamination with priority toxicants of the Seversky Donets River in 2024–2025
Korablinа I.V., Kosenko Yu.V., Alekseevа N.V., Dolzhanov P.B.
Abstract
Background. The study of the habitat conditions for aquatic biological resources in the Seversky Donets River is of great ecological and fisheries importance. Relevance. The high level of anthropogenic pressure on the Seversky Donets River necessitates regular comprehensive environmental monitoring. The aim of this study is to examine the hydrochemical regime and pollution with priority toxicants of the Seversky Donets River as a water body of the highest fisheries category. Methods. The results of an investigation of hydrochemical parameters and toxicant contamination of the Seversky Donets River ecosystem, based on the data collected in the area from Veselaya Gora settlement to Ust-Donetsk urban-type settlement in August 2024–2025 and in November 2024, are presented. Sampling of water and bottom sediments was conducted using standard methods. Determination of chemical parameters was performed in accordance with procedures approved at the federal level. Results. The oxygen and salinity regimes in the Seversky Donets River did not limit the functioning of freshwater and semi-anadromous fish species. Increased concentrations of nitrite nitrogen and phosphate phosphorus are indicative of anthropogenic water pollution. The local exceedance of the MACfishery for manganese in water by up to 13.0 times and for mercury by up to 15.8 times likely results from the combined influence of both natural and anthropogenic factors. The accumulation of petroleum products in bottom sediments in certain parts of the investigated area has been recorded, reflecting the chronic oil pollution of this water body. Conclusion. The environmental conditions for aquatic organisms in the Seversky Donets River in 2024–2025 were characterized as relatively favorable for their functioning.
Keywords: Seversky Donets River, hydrochemical regime, priority toxicants, water, bottom sediments, aquatic organisms
Features of the hydrochemical regime during the operation of the organic and carbonate pumps in the Northeastern Black Sea in 2022
Chasovnikov V.K., Chasovnikov D.V., Rebetskaya E.A., Fedorova P.A.
Abstract
Background. As a result of the functioning of the biological carbon pump (BCP), atmospheric carbon is converted into organic forms (organic pump) or inorganic forms such as calcite (carbonate pump). Relevance. The ocean accounts for nearly half of global carbon sequestration, making the study of these processes a relevant task in marine research. The aim of this work is to determine the hydrochemical conditions underlying the functioning of the organic and carbonate pumps in the Northeastern Black Sea in 2022 and to identify the factors responsible for the shift in their seasonal dynamics. Methods. In 2022, 14 expedition cruises (70 stations, 210 sampling depths) were carried out, with water sampling performed in the 0–50 m layer; temperature, salinity, and the concentrations of phosphorus, silicon, and inorganic nitrogen were measured, and quantitative and taxonomic analysis of phytoplankton was conducted. Results. An anomalous alteration of the timing of Emiliania huxleyi bloom (carbonate pump), which lasted from early June to late July, was recorded, while the period of diatom dominance (organic pump) shifted to August–September. Such a delayed and prolonged coccolithophore bloom, shifted by a full month, was documented for the first time. In 2022, the carbonate pump period was characterized by the following distinctive hydrological and hydrochemical features: stable water stratification with a shallow thermocline (located above the long-term average level) and high phosphorus concentrations combined with inorganic nitrogen deficiency. Conclusion. It was determined that the anomalous shift in the timing of carbonate pump functioning in 2022 resulted from a combination of factors: uncharacteristically stable stratification, persistent nitrogen deficiency, and elevated phosphorus concentrations in the active layer of the sea, which provided E. huxleyi with a competitive advantage for almost two months. Significant differences between the carbonate and organic pump dominance periods were revealed in temperature, salinity, silicon and nitrogen concentrations, and in the Si:N ratio. These findings improve our understanding of the switching mechanisms of the biological carbon pump in the Black Sea.
Keywords: Black Sea, hydrochemical regime, biogenic elements, diatoms, coccolithophore bloom shift, carbonate pump, organic pump
Biology and Ecology of Aquatic Organisms
Effects of mixed diets on the growth and reproductive success of Arctodiaptomus salinus (Daday, 1885) (Copepoda, Calanoida)
Aganesova L.O.
Abstract
Background. Calanoida copepods are a crucial component of zooplankton and serve as a high- quality live food for fish and crustacean larvae in aquaculture. Relevance. Mixed microalgae feeds offer a balanced diet for copepods (in terms of lipids, proteins, carbohydrates, and micronutrients), improving their growth, reproduction, and nutritional value. The aim of this work is to investigate the development, survival, and reproductive characteristics of Arctodiaptomus salinus (Daday, 1885) when fed with microalgal monocultures (Rhodomonas salina (Wisłouch) D.R.A. Hill &
R. Wetherbee, 1989, Dunaliella salina (Dunal) Teodoresco, 1905) or their mixture under experimental conditions. Methods. In this work, accumulative and individual cultivation modes for aquatic organisms were used. Results. The highest average daily fertility (4.2 eggs per female-1 day-1) and the shortest period between clutches (2.5 days) were obtained when the copepods were fed a mixture of the microalgae R. salina + D. salina. The highest hatching rate of viable nauplii (~80 %) was observed when the copepods were fed with R. salina and a mixture of R. salina + D. salina, whereas the lowest (~2 %) occurred when they were fed with D. salina. The minimum duration of ontogenesis (18–19 days) was recorded when the copepods were fed with R. salina and a mixture of R. salina + D. salina. Conclusion. The monoculture of microalgae R. salina is the optimal food source for A. salinus. The combination of R. salina + D. salina improves the reproductive performance of copepods while reducing cultivation costs, ultimately leading to more efficient aquaculture production.
Keywords: copepods, Arctodiaptomus salinus, microalgae, a mixture of microalgae, development, survival rate, reproduction, aquaculture
Spring and summer zooplankton of Kulikov-Kurchansky Limans
Kornienko G.S., Antsupova A.M.
Abstract
Background. This article presents the results of studies conducted in 2018–2021 and 2023 on the quantitative development and species composition of spring and summer zooplankton in the Kulikov- Kurchansky group of limans, as well as characterizes long-term changes in zooplankton species composition and biomass across two seasons (spring and summer). Data on zooplankton species diversity are presented, and the dominant zooplankton groups and prevailing species are identified. Relevance. At present, information on the species diversity and quantitative development of zooplankton in the Kulikov-Kurchansky group of limans remains very scarce. This work is aimed at revising and updating the available data. The aim of this work is to compare the abundance, biomass, and species diversity of spring and summer zooplankton in Kulikov-Kurchansky Limans in 2018–2021 and 2023 with data from previous years. Methods. Zooplankton samples were collected using a 5-liter Patalas plankton bathometer, followed by filtering 100 liters of water through a small Apstein net with No. 68 mesh gauze. The samples were fixed in a 4 % formalin solution. Laboratory processing was performed using an MSP-2 stereoscopic microscope. Zooplankton biomass was calculated using tables for determining individual organism weights. Results. A comparison of the qualitative and quantitative zooplankton dynamics revealed that the number of zooplanktonic species exceeds that recorded in previous years by more than twice. During the study period, rotifers prevailed in the zooplankton of Kulikovsky Limans in terms of abundance, accounting for 88.4–99.1 % in spring and 52.1–80.1 % in summer. The proportion of rotifers also increased in the Kurchansky Liman: from 2.3 % to 80 % in spring and from 13.7 % to 80.4 % in summer. Rotifers, in addition to dominating zooplankton abundance, also make a significant contribution to biomass: up to 96.6 % in spring and up to 28.9 % in summer. The proportion of cladocerans in Kurchansky Liman decreased from 3.9–18.2 % in 2018 to complete absence in subsequent years. Copepods dominated the zooplankton of Kurchansky Liman, comprising up to 99.7 % (3.04 g/m3) of total biomass in spring and up to 91.3 % in summer. In Kulikovsky Limans, copepods accounted for between 1.1 % (in spring) and 46.0 % (in summer) of the total zooplankton abundance. Conclusion. The limans of Kulikov- Kurchansky group retained their fishery potential in terms of fish farming on natural food resources.
Keywords: limans, Kulikovsky, Kurchansky, zooplankton, species diversity, abundance, biomass
Results of experimental production and rearing of juvenile narrow-clawed crayfi sh Pontastacus leptodactylus (Eschscholtz, 1823) in industrial culture
Pavlyuk A.A., Sergeeva S.G., Belousov V.N., Polin A.A., Strigunov A.M.
Abstract
Background. One of the ways to meet the increased demand for crustacean products is to grow narrow- clawed crayfish in artificial conditions. Relevance. The breeding of crayfish in trays, aquariums, and, more recently, in recirculating aquaculture systems has been carried out quite successfully; however, the issues of biotechnics require its thorough examination and improvement, including the identification of optimal conditions for crayfish cultivation and feeding. The aim of this study is to develop standards and the main elements of the technological procedure for obtaining viable juveniles of the narrow-clawed crayfish—in particular, the conditions for transporting and keeping mature females, the stocking density and growth rate of juveniles, as well as their survival rate depending on the rearing environment. Methods. The subjects of this study were the breeders of the narrow-clawed crayfish Pontastacus leptodactylus (Eschscholtz, 1823) harvested in their natural habitat, as well as its juveniles. The experiment was conducted using fish farming and biological methods, as well as hydrochemical and biotechnical research techniques, in accordance with generally accepted procedures. Results. The study was conducted in several stages: catching, transporting, and selecting the breeders; keeping the breeders in culture environment; obtaining early juveniles; and rearing the juveniles. The total duration of the experiment was 6 months. The experiment investigated the growth rates and survival of juveniles under group and individual rearing conditions. The stocking density varied from 22 to 330 ind./m2. In each case of group rearing, a large number of juveniles died due to cannibalism directed at molting individuals. The presence of shelters and increased feeding rations only slightly reduced the level of cannibalism. The juvenile narrow-clawed crayfish actively fed on the artificial feed and on the offered live and plant-based feeding options introduced according to the developed feeding scheme. Conclusion. Based on the experimental work conducted on obtaining and rearing juvenile narrow-clawed crayfish in industrial culture, the optimal parameters for its production and rearing have been identified. The main biotechnical stages of harvesting, transportation, adaptation, and keeping egg-bearing females have been described. The growth and survival rates of juveniles have been analyzed in relation to their stocking density, and the need for shelters has been determined. A feeding scheme incorporating artificial and live feeds has been developed.
Keywords: recirculating aquaculture system (RAS), narrow-clawed crayfish, juveniles, stocking density, cannibalism, survival rate, feeding
Spatiotemporal variability of the biomass of Aurelia aurita (Linnaeus, 1758) jellyfi sh in the waters of the Russian Black Sea shelf in the summer season
Piontkovski S.A., Zagorodnyaya Yu.A., Samotoy Yu.V., Baiandin A.S., Artamonov Yu.V., Skripaleva E.A.
Abstract
Background. Over the past 15 years, expeditionary studies have been conducted on the Russian Black Sea shelf. They included comprehensive measurements of the physical, chemical, and biological characteristics of the pelagic ecosystem. One of the objectives of these studies was to assess the spatial distribution of the biomass of Aurelia aurita (Linnaeus, 1758) jellyfish, a common zooplankton species. Relevance. The high abundance of jellyfish in the waters of the Black and Azov Seas currently negatively affects the quality of recreation for citizens spending their vacations on the coast. At the same time, the proliferation of jellyfish in plankton also has a positive aspect associated with their harvesting and use as food and in the production of pharmaceuticals. The aim of this study is to identify trends in long-term variability of the spatial distribution and biomass of A. aurita jellyfish in the waters of the Russian Black Sea shelf from Adler to the southern coast of Crimea. Methods. This study utilizes the data collected during summer expeditions aboard the R/V “Professor Vodyanitsky” in 2010–2025. Fieldwork on each cruise lasted 20–26 days. The abundance and size of individuals were determined in samples collected with an ichthyoplankton net with a mesh size of 400 µm. Results. It has been shown that, in the summer season, the A. aurita population is dominated by medium-sized individuals (40–50 mm) ranging from 10 to 160 mm. No statistically significant monotonic along-shelf trends were found in the spatial distribution of jellyfish biomass during field surveys conducted in the summer and autumn of 2025. The biomass varied widely: from 1 to 984 g/m2. The biomass variation coefficient during surveys extending from Adler to the southern coast of Crimea exceeded the seasonal and long-term variability coefficients. Conclusion. On the Crimean shelf (with the greatest number of sampling catches), long-term biomass variability did not show a statistically significant trend. The average long-term biomass for this region was 238±227 g/m2, and the total biomass of A. aurita on the Russian shelf (from Adler to the southern coast of Crimea) was estimated at ~2 million tons.
Keywords: Black Sea, zooplankton, jellyfish, biomass, Aurelia aurita
Ecological assessment of watercourses of the Sudogda River Basin by macrozoobenthos characteristics
Rostunov A.O., Savelyev O.V., Trifonova T.A.
Abstract
Background. At present, supervisory authorities focus mainly on the environmental monitoring of aquatic ecosystems of large rivers, while small watercourses receive comparatively less attention. However, small rivers and streams serve as the primary recepients of contamination originating from the heavily industrialized areas and agricultural landscapes. Relevance. Small rivers are more vulnerable to pollution than large ones, as their ecosystems are less resilient. Anthropogenic pressure on small rivers is relatively high due to their exploitation in industry, agriculture, and tourism. However, in recent years, the number of monitoring stations on small rivers has been steadily decreasing. Aim. This article aims to assess the current ecological status of watercourses in the basin of the Sudogda River (a tributary of the Klyazma River) based on a study of macrozoobenthos species composition. A comparative analysis of the taxonomic composition and functioning of macrozoobenthos was conducted for the main channel of the Sudogda River and for its small tributaries. Methods. Major ecosystem characteristics have been identified based on the functional groups of macrozoobenthos, and biodiversity indices (Shannon–Weaver Diversity Index, Simpson's Diversity Index, and Pielou's Evenness Index) have been calculated; the saprobic status (according to M.V. Chertoprud), water quality class (according to S.G. Nikolaev), and Goodnight–Whitley Index have also been determined. Results. The calculated ecological indices reveal a high level of pollution in the Sudogda River Basin, with the river's tributaries being the most heavily impacted due to their shallow depth, slow current, and location within forested and marshy areas. The main sources of pollution are industrial and agricultural facilities, located primarily along the banks of small watercourses. Conclusion. One of the main conclusions of this study is the necessity to restore the system of hydrological monitoring stations on small rivers, as these watercourses often serve as the primary sources of pollution for larger rivers.
Keywords: Sudogda River (a tributary of the Klyazma River), small rivers, macrozoobenthos, bioindication, saprobic status, biodiversity, eutrophication, self-purification
Autumn dominance of Asterionella formosa Hassall, 1850 in a mesotrophic lake of the temperate zone: the role of mixing and nutrient availability as counterbalances to temperature
Solodovnik A.V., Tyulin D.Yu., Nikitenko A.I., Zhernakov I.A., Zdrok A.V.
Abstract
Background. The dynamics of key phytoplankton dominant species determine the trophic structure and productivity of freshwater ecosystems. The diatom Asterionella formosa Hassall, 1850 plays a crucial role as a primary producer and forms the basis of the food supply. Relevance. The factors regulating the dominance of A. formosa in temperate latitudes, particularly the role of temperature versus mixing regime and availability of biogenic elements, remain a matter of debate. For mesotrophic Lake Senezh, quantitative data on the ecology of this species have been lacking until now. The aim of this work was to quantify the contribution of A. formosa to the phytoplankton community and to identify the key abiotic factors controlling its autumn dynamics under homothermy. Methods. In September 2024, phytoplankton and water samples were collected at three stations in Lake Senezh for hydrochemical analysis. Sample processing followed standard methods. Statistical analysis included correlation calculations to identify relationships between parameters. Results. A. formosa was the absolute dominant in the phytoplankton community. Its maximum abundance and biomass were recorded at the coldest station (3.2 °C), with no significant correlation with temperature found. The water body was in a state of complete homothermy with non-limiting concentrations of phosphates, nitrogen, and iron. A positive correlation was found between the biomass of diatoms and cladocerans of the family Daphniidae. Conclusion. The autumn dominance of A. formosa is driven not by temperature but by a synergy of factors: homothermy ensuring mixing and preventing sedimentation; a non-limiting background level of the investigated biogenic elements (P, N, Fe); and reduced trophic pressure. This species represents a key food resource for zooplankton. Its mass development can serve as a bioindicator of the autumn circulation phase with a balanced regime of biogenic elements in mesotrophic lakes.
Keywords: diatoms, Asterionella formosa, seasonal dynamics, homothermy, biogenic elements, mixing, trophic interactions, Lake Senezh, phytoplankton, bioindication
Informational Messages
On the upcoming 5th International Scientifi c and Practical Conference “Biological Diversity: Study, Conservation, Restoration, Rational Use”, 15–20 September, 2026 (Kerch State Maritime Technological University, Kerch, Russia)