CONTENT
Review Articles
Diversity and indicator properties of algae in continental waters of the North Caucasus
Barinova S.S., Bragina T.M.
Abstract
Background. The North Caucasus is a vast territory at the boundary between Europe and Asia, with an elevation gradient of up to 5,000 meters, rich in aquatic resources, the diversity of which remains poorly studied. Relevance. Accumulating data on algal composition is essential for studying the region's response to climatic and environmental gradients. The aim of this work is to compile and analyze published data on algal diversity in continental water bodies. Methods. Accumulation of biodiversity data, standardization of species names according to modern taxonomic classification, selection of indicator species for various environmental conditions, statistical analysis of their distribution across indicator groups, and identification of threatened species based on IUCN categories were performed using published literature and international databases, with application of Microsoft Access and Microsoft Excel. Results. Data on algal and cyanobacterial diversity published in articles and books in Russian and English currently encompass 1,099 taxa below the rank of genus. Diatoms, green algae, and cyanobacteria dominate, forming a major part of the plankton and benthos of freshwater bodies with moderate salinity and temperature, indicating water quality classes 2–3. A total of 257 species belonged to 8 IUCN categories, accounting for 23 % of the species composition, and 26 of these were classified as threatened (categories 1–3). Conclusion. The analysis of published data has made a substantial contribution to the study of continental aquatic habitats. Diatoms, green algae, and cyanobacteria were the dominant components of the identified algal diversity. Up to 98 % of the species were water quality indicators, and 26 of them were classified as threatened. The compiled indicator database can be applied in water quality monitoring.
Keywords: North Caucasus, algal diversity, water quality bioindicators
Biology and Ecology of Aquatic Organisms
Food resources of benthivorous fish in the Lower Don River
Zhivoglyadova L.A., Elfimova N.S., Vekhov D.A., Khrenkin D.V., Afanasyev D.F.
Abstract
Background. The Lower Don is one of the most heavily transformed river systems in southern Russia, where reproduction of anadromous and semi-anadromous fish is largely supported artificially. Relevance. Assessing the condition of the food base for fish is an essential component in substantiating the number of released juveniles and determining the carrying capacity of the ecosystem. The aim of this work is to assess the current status and spatial distribution of forage zoobenthos in the lower reaches of the Don River as a food resource for benthivorous fish during the summer period. Methods. The studies were conducted in 2019–2024 along the river stretch from the Tsimlyansk Reservoir to the river mouth. Samples were collected at standard transects near stanitsa Romanovskaya, Semikarakorsk, stanitsa Manychskaya, Aksay, khutor Shmat, and Lotsmeystersky Post. The total number of sampling stations over the entire study period was 79. Results. No statistically significant differences in the quantitative characteristics of forage benthos were detected among the studied transects (Kruskal–Wallis test: H=7.5; p>0.05). The abundance of forage organisms was determined by substrate type (Kruskal–Wallis test: H=20.7; p<0.05). The lowest mean biomass of forage benthos was recorded in areas dominated by sand (1.7 g/m2), whereas the highest mean biomass was observed on shell substrates (550.6 g/m2). Conclusion. Longitudinal differentiation of zoobenthos was most clearly expressed at the level of faunal composition, whereas the quantitative development of forage benthos was primarily determined by the type of bottom substrate. The biomass of the forage benthic fraction, calculated as a weighted mean taking into account the occurrence frequency of areas with different types of bottom sediments, was 95.8 g/m2.
Keywords: zoobenthos, fish food resources, invasive species, ecosystem carrying capacity
Zhondareva Ya.D., Rylkova O.A., Kharchuk I.A., Borovkov A.B.
Abstract
Background. The marine microalga Porphyridium purpureum is characterized by high productivity, resistance to external factors, and a rich content of biologically active substances: phycobiliproteins, including ß-phycoerythrin; exopolysaccharides with antioxidant, anti-inflammatory, and antiviral activity; polyunsaturated fatty acids, including omega-3; carotenoids; vitamins; and enzymes. This makes it a multifunctional resource for biotechnology, aquaculture, cosmetics, and the food industry. Relevance. To cultivate microphototrophs, it is essential to assess the physiological state and quantitative (structural and functional) parameters of their cells at different growth stages. Flow cytometry is a powerful, high-throughput method that provides real-time data on the abundance, granularity, and fluorescence of microalgal cells, which warrants its frequent use in studying algal cultures. However, P. purpureum is known to secrete gel-forming polysaccharides during growth that promote cell adhesion and aggregate formation, which, in turn, makes the culture suspension unsuitable for cytometric studies. The aim of this article was to test various methods for the preliminary sample preparation of the microalga Porphyridium purpureum culture for subsequent cytometric analysis. Methods. This study utilized a strain of the red marine microalga Porphyridium purpureum (Bory) K.M. Drew & R. Ross, 1965 (IBSS-70), obtained from the Collective Use Center “Collection of Hydrobionts of the World Ocean” of the Federal Research Center “A.O. Kovalevsky Institute of Biology of the Southern Seas, Russian Academy of Sciences”. Flow cytometry, light microscopy, and scanning electron microscopy were used in the study. Sample preparation of the suspension included filtration, physical separation of aggregates (ultrasonic treatment), and physicochemical treatment (ultrasonication + methanol). Results. It has been shown that the abundance of P. purpureum after physical and physicochemical treatment, with and without filtration, did not differ significantly (paired t-test, p>0.05). The addition of methanol at a final concentration of 10 % did not induce significant changes in the physiological state and structural parameters of P. purpureum, including cell size, granularity, or pigment fluorescence intensity (in all cases, paired t-test, p>0.05). Thus, no significant toxic effect on microalgal cells was detected. Conclusion. The developed sample preparation protocol allows for the effective breakdown of cell aggregates without adversely affecting cell morphology and physiological state and can be used in cultivation of microalgae for biotechnological purposes.
Keywords: Porphyridium purpureum, flow cytometry, sample preparation, cell aggregation, ultrasonication, methanol, granularity, fluorescence, polysaccharides, cell abundance
Saenko E.M.
Abstract
Background. The Azov Sea has an unstable salinity regime, characterized by alternating periods of desalination, stabilization, and salinization. The dynamic nature of hydrological conditions and climate changes leads to gradual ecosystem disturbances. Relevance. In this regard, it is of interest to study the functioning of populations of benthic community representatives within the supralittoral and upper sublittoral zones, which are the most susceptible to extreme environmental factors and climate changes. The aim of this study was to assess changes in the qualitative composition of the Pontogammarus maeoticus (Sovinskij, 1894) population in the Azov Sea and to evaluate the impact of environmental factors (salinity) on it. Methods. The study was based on research conducted in 2008–2024 that assessed the condition of the pontogammarus population in the Azov Sea by such parameters as length– weight and sex composition, and fecundity, with regard to a specific environmental factor (salinity). Pontogammarus samples were collected in the supralittoral zone using a benthic frame and a trap, and in the upper sublittoral zone at a depth of 0.5 m using a trap. The samples were fixed in a 4 % aqueous formaldehyde solution. The laboratory processing included the determination of species, sex, dimensional characteristics, counting the number of individuals in the sample, and measuring the individual length and weight of the crustaceans. The weight was measured in several (or a group) of individuals of the same length. Results. The qualitative composition (length–weight and sex composition, fecundity) of P. maeoticus aggregations in the Azov Sea was examined for the periods of its salinization from 10.66 to 13.24 ‰ (2008–2015) and subsequent stabilization of its salinity regime in the range of 14.91–15.29 ‰ (2022–2024); it was also investigated for Taganrog Bay, where salinity increased from 6.56 to 11.05 ‰ (2008–2024). The relationship between these parameters was analyzed, as well as their shifts with salinity changes within the species natural salinity range. Conclusion. Under the conditions of dynamic salinization of the Azov Sea, including Taganrog Bay, the adaptation of P. maeoticus is expressed in the constant restructuring of the qualitative parameters of its population. The most stable parameters in the context of pontogammarus adaptation to the salinity increase are length, weight (length–weight composition of the population), and the period of reaching sexual maturity. Under long-term salinity increase within the optimal salinity range, acclimatization to this factor occurs through reduced fecundity and prolongation of the life cycle. If salinity rises into the critical range, adaptation to the new conditions occurs through a shortened life cycle in most of the population and through an increased proportion of females and juveniles.
Keywords: Azov Sea, Taganrog Bay, Pontogammarus maeoticus, salinity, length–weight composition, sex composition, fecundity, adaptation, dependence
Ichthyofauna of Marine and Inland Water Bodies
Kochetkov N.I., Nikiforov-Nikishin D.L., Krivosheev F.A., Glebova I.A., Gladysh N.S.
Abstract
Background. Aplocheilus lineatus (Valenciennes, 1846), or the striped panchax, is a non-annual oviparous killifish of the suborder Aplocheiloidei. The development of aquaristics and the use of this species as a biological control agent for reducing mosquito larvae abundance have contributed to its expansion beyond its natural range, making it an attractive research subject. Relevance. Investigating the early ontogeny of non-annual killifish is essential for understanding the evolution and unique adaptations of annual species, particularly embryonic diapause. The aim of this study is to describe the chronology and features of embryonic development in the non-annual species Aplocheilus lineatus. Methods. Eggs from 6-month-old individuals were incubated in Yamamoto's solution at 25.3 °C. Embryonic development was monitored under a microscope in the grooves of a Goryaev chamber: every half hour until the end of epiboly, and subsequently every 6 hours. Egg survival and larval hatching rates were evaluated. Results. It was established that this species exhibits a specific pattern of meroblastic cleavage: at the 16-blastomere stage, a portion of the cells separates from the yolk; the cells retain a rounded shape up to the discoblastula stage (4 hours post-fertilization, hpf). The epiboly stage (6–18 hpf) is characterized by an intermediate blastoderm architecture with visibly distinct deep cells, the number of which appears to exceed that observed in annual killifish species. Organogenesis proceeds in a manner typical for teleosts: the first somites appear by 26 hpf, and blood circulation begins by 50 hpf. An adaptive heterochrony was identified—specifically, early pigmentation of the body and yolk sac by melanophores (starting at 38 hpf, the 24-somite stage), which precedes the differentiation of the retinal pigment epithelium. The hatching of fully developed larvae occurs between 248 and 264 hpf. However, a delayed hatching of up to 3–4 days was recorded in 30 % of the embryos. Conclusion. It was found that, despite a high egg survival rate (81 %), delayed hatching is observed in one-third of the embryos, which likely serves as an ecological adaptation to unstable environmental conditions.
Keywords: early ontogenesis, cyprinodontiformes, morphogenesis, pigmentation, cleavage, adaptation
Aquaculture and Methods of Artificial Reproduction
Pyatikopova O.V., Bedritskaya I.N., Menkova A.V., Sapakhova L.Kh., Ankesheva B.M.
Abstract
Background. The self-purification capacity of water bodies is a key indicator of their ecological well-being. Microbiological parameters enable the assessment of the intensity and effectiveness of self-purification in flowing water bodies, particularly in areas of cage fish farming. Relevance. With increasing anthropogenic pressure and the development of aquaculture, the risk of inhibition of self- purification processes increases, necessitating regular sanitary-microbiological monitoring of water bodies. The aim of this work was to assess the sanitary-microbiological state and the capacity for biological self-purification of natural water bodies in the Astrakhan Region (Khurdun River, Tsarev River, Tri Yerika (Three Yeriks) Channel, and Novostanka River) in the areas where cage fish farms are located. Methods. Sanitary-microbiological studies of water bodies in the Astrakhan Region were carried out in the vicinity of 4 operating cage fish farms in 2023; samples were processed in a laboratory setting using the pour plate method. Water samples were collected in spring (April 11, 2023), summer (July 19, 2023), and autumn (September 20, 2023) from the surface horizon at three points: 500 m upstream of the cage farms (background), immediately downstream of the cages, and 500 m downstream of them. The total microbial count (TMC at 22 °C, TMC at 37 °C) was determined. The self-purification coefficient (Kc) was obtained by calculation. Results. The water quality of the surveyed natural water bodies of the Astrakhan Region at the background points during the study was relatively satisfactory, with no exceedance of the standard for TMC at 37 °C. At the location of fish farms, an increase in this parameter was observed in summer. At a distance of 500 m downstream of the farms, exceedance of the standard for TMC at 37 °C was recorded for the cage farms characterized by the largest fish-farming area. Irrespective of their locations, the examined sections of the water bodies showed a low capacity for bacterial self-purification. Conclusion. The operation of cage farms in flowing water bodies can both enhance and reduce the rate of water self-purification processes. In some cases, the spread of fecal contamination was traced up to 500 m downstream of the fish farms.
Keywords: self-purification of water bodies, anthropogenic impact, cage fish farms, microbiological parameters, eutrophication, self-purification coefficient
Stazhok T.V., Guleichuk N.I.
Abstract
Background. Given the acute water shortage in the Donbas, the search for alternative water sources is urgent. Mine water generated during dewatering of decommissioned coal mining facilities is an understudied but potentially valuable resource. Despite its pollution and heterogeneous physicochemical composition, with proper treatment this water can be used in agri- and aquaculture, in the industrial sector, and for the technological needs of the population. Relevance. The preserved engineering facilities and infrastructure of decommissioned mines, as well as functioning dewatering systems provide the basis for the possibility of their use for establishing aquaculture enterprises, which, prospectively, could help lower social tensions by employing former coal workers, reduce logistics costs, and ensure product availability. In the context of increasing global and regional shortages of food and water, aquaculture is becoming a key factor in ensuring food security. Aim. This study aims to explore the possibility of creating fish farming facilities on the sites of decommissioned mines. This approach can contribute to the development of the regional economy in the context of water scarcity in this region. Methods. The materials presented in this article are based on an analysis of the published literature. Particular attention was given to the physicochemical characteristics of mine water and its compliance with regulatory standards. This study incorporates data on scientific and technical pilot projects on mine water treatment (purification) to potable quality, developed by the State Budgetary Institution “Dongiproshakht” for the cities of Torez and Snezhnoye, as well as the experience of specialized fish farming enterprises. Data on the volume of mine water pumped out were obtained from the Main Department for Mines Restructuring of the Donetsk People's Republic. Results. An analysis of the potential for using existing infrastructure of decommissioned mines, including dewatering systems, was conducted. Mines in the Donetsk People's Republic were selected as a case study, for which water composition data were examined. The specific features of decommissioned mine infrastructure that could be adapted for the creation of aquaculture facilities, ensuring year- round production, were investigated. Conclusion. In the Donbas, where water scarcity coincides with the existence of numerous decommissioned mines, the development of aquaculture facilities using mine water represents a promising solution that requires further pilot projects and practical testing of the proposed initiative.
Keywords: fish culture, mine water, rearing environment, facility structure, settling ponds, water treatment facilities
Informational Messages
Kosenko Yu.V., Bragina T.M., Lezgovka N.A., Khochkiyan D.A.
Abstract
Background. The water bodies of the Lower Don are subject to severe anthropogenic pressure, resulting in environmental changes unfavorable for aquatic bioresources, as well as other adverse effects. Relevance. Intensive water use in the Semikarakorsky District of the Rostov Region for irrigated agriculture, municipal supply, and industrial needs, along with flow regulation and water pollution, necessitates continuous monitoring of the Don River's ecological state to assess its hydrochemical regime and contamination with toxicants. This research is particularly relevant in view of the severe water pollution recorded in the study area in late spring 2025. The aim of this study was to analyze key hydrochemical parameters and contamination with priority toxicants near the town of Semikarakorsk (Rostov Region) in autumn 2025 in the context of the results of spring surveys that documented significant pollution in the study area. Methods. Standard methods approved at the federal level were used to collect surface water and riverbed sediment samples from the Don River at a station near Semikarakorsk (Rostov Region) and to determine their chemical parameters. Results. This article presents the results of environmental analytical monitoring of surface waters and bottom sediments in a section of the Don River near Semikarakorsk. Monitoring conducted in this aquatic area in September 2025 revealed no contamination of bottom sediments with petroleum products, cadmium, and manganese. A decrease in the intensity of phytoplankton “blooming” (98 % oxygen saturation) and the concentration of suspended solids in the water was recorded; in terms of the trophic index, the water was characterized as hypertrophic (7.6 units). The total dissolved solids of the water were 764 mg/dm3, being favorable for aquatic organisms. Conclusion. The contamination of bottom sediments in the Don River with petroleum products and cadmium, recorded near Semikarakorsk in May 2025, was short-term and localized and did not lead to mass mortality of aquatic bioresources. In September 2025, the environmental conditions in the Lower Don near Semikarakorsk were characterized as favorable for all species of aquatic bioresources.
Keywords: Don River channel, Semikarakorsk, ecological monitoring, hydrochemistry, toxicants, surface waters, bottom sediments, aquatic bioresources