CONTENT
Environmental Concerns and the State of Aquatic Environment
Estimates of the surge phenomena eff ects on the potential for heavy metal compounds accumulation in the Don Delta soil during the low water period (2007–2020)
Berdnikov S.V., Gerasyuk V.S., Kleshchenkov A.V., Kulygin V.V., Likhtanskaya N.V., Sheverdyaev I.V.
Abstract
Background. The contamination of the Lower Don floodplain soil by potentially toxic elements (PTE), which include heavy metal (HM) compounds, is associated with the introduction of these substances with river water during high water periods, when the delta is flooded by flood water and suspended sediments and various chemical compounds migrating within them accumulate on its territory. During the current prolonged period of low water, spring floods are absent, and flooding occurs mainly by surge sea water from Taganrog Bay. Relevance. A multidisciplinary approach based on the data collected during field studies and observations conducted at hydrological stations, as well as on the results of mathematical modeling makes it possible to reveal how PTEs migrating as part of suspended sediments can contaminate the Don Delta soils and how this is related to surge phenomena. The aim of this work is to describe the conditions of the Don Delta pollution with PTEs, primarily HM compounds, in the context of low water and decreasing solid runoff of the Don River and the surge phenomena influence. Methods. To describe the transport and transformation of suspended solids, we used an approach based on the joint application of the detailed hydrological model HEC-RAS adapted to the conditions of the Don River estuary (DonDeltaHECRAS) and the dynamic model of the balance of water and substances transported by water masses (DonDeltaBalanceModel). Results. Estimates of HM introduction with runoff to the Don River estuary and its contribution to the “filtration” of chemical compounds on the paths of their migration with river water to the Azov Sea have been obtained. Calculations of suspended sediment dynamics for six types of surges have been carried out, and estimates of suspended sediment accumulation in the Don Delta have been obtained. Estimates of HM input into the upper soil layer of the Don Delta during surges have also been obtained. Conclusion. The source of pollution of the delta with PTEs is their anthropogenic runoff. While during high water and floods the accumulation of PTEs occurs due to the river contribution, during low water and surges, anthropogenic riverine PTEs, after their biogeochemical transformation on the estuarial seashore, in Taganrog Bay, and the Azov Sea, return to the delta via surges. The role of the delta and the estuary as a “filter” on the migration path of dissolved and suspended forms of PTEs from the river to the sea has been transformed.
Keywords: heavy metals, Don Delta, low water, surge phenomena, anthropogenic impact
Ecological and fi sheries aspects of the formation of the modern hydrological regime of the water bodies of the Azov–Don Region. Part 1: Anthropogenic and climatic changes in the fl ow of the Don River; fi sheries requirements for the water bodies of the Lower Don
Zhukova S.V., Podmareva T.I., Taradina E.A., Lutynskaya L.A., Burlachko D.S., Karmanov V.G., Bugaev L.A., Belousov V.N.
Abstract
Background. This study, consisting of two parts, examines the ecological and fisheries aspects of climatic and anthropogenic transformations of the hydrological regime in the Don River Basin, the requirements of the fisheries industry to the Lower Don water supply, both prescribed and actually met (Part 1), as well as the issues of fulfilling the fisheries needs by the floodplain spawning grounds of the Lower Don in their current geobotanical state, changes in the habitat conditions of the aquatic bioresources in Taganrog Bay utilizing it as a receiving reservoir for the adaptation of juvenile fish to marine conditions, and the efficiency of the Ust-Manych fish passage channels during the spawning season (Part 2). The functioning of the aquatic and near-water ecosystems of the Azov–Don Region along with the processes of natural reproduction of fish depend on the hydrological regime of the Don River, the degree of impact of anthropogenic and climatic factors, and the methods of water resource management in the Don Water Management Complex (DWMC). Relevance. The ecological and fisheries aspects of the formation of the modern hydrological regime in the Lower Don Basin, as well the regulatory practices for the water regime of the Tsimlyansk Reservoir and their legal implications are considered; the main reasons for the limited possibility of organizing water releases with ecological and fisheries purposes are stated. The aim of this work is to assess the possibilities of meeting the demands of fisheries with the water resources of the Tsimlyansk Reservoir in the context of changes in the modern hydrological regime of the Don River. Methods. The data on the flow of the Don River collected at stanitsa Razdorskaya and published in the annual reference publications of Roshydromet (to 1991) have been used, as well as the data on the average monthly and maximum water consumption (stanitsa Razdorskaya) for the period 1992–2023 that were obtained from the North Caucasus Office for Hydrometeorology and Environmental Monitoring (SK UGMS) on a contractual basis. The daily monitoring data for the hydrological regime of the Tsimlyansk Reservoir have been acquired through the website of the Don Basin Water Administration (DBVU). Archival and published data on the investigated subject matters have also been used. Methods of mathematical statistics and graphanalytical construction have been applied during the data processing. Results. In the Don River Basin, the trend for a decrease in the volumes of annual and spring runoff under the influence of climatic and anthropogenic factors is observed, which obstructs the flooding of the floodplain spawning grounds and hinders the natural reproduction processes. Conclusion. In the process of integrated use and intersectoral distribution of water resources of the Tsimlyansk Reservoir, the economic feasibility is prioritized over environmental sustainability. The spring ecological and fisheries-related water releases have not been possible in the Lower Don Basin in recent years (1994–2024).
Keywords: Lower Don, flow change, Tsimlyansk Reservoir, ecological and fisheries-related water releases, water consumption, runoff volume, inflow, discharge, water level
Habitat conditions of aquatic bioresources in the Lower Don water area (2015–2024)
Kosenko Yu.V., Korablina I.V., Gorgola L.G., Baskakova T.E., Elfi mova N.S.
Abstract
Background. The hydrochemical and toxicological regime of the Lower Don has a major impact on the habitat conditions of semi-anadromous fish species and the ecological state of the Azov Sea. Relevance. Currently, the Lower Don water area is a transformed natural ecosystem, the state of which has been significantly deteriorating in recent years. Environmental problems of the Lower Don are also associated with global natural climatic factors, such as changes in atmospheric circulation and a significant decrease in surface runoff observed from 2007 to the present. The aim of this work is to study the hydrochemical regime and toxicological state of the Lower Don water area in 2015–2024. Methods. This article presents the results of studies of the hydrochemical regime and pollution with priority toxicants in the ecosystem of the lower reaches of the Don River, from stanitsa Romanovskaya to its mouth at the Azov Sea, in the spring, summer, and autumn seasons for the period 2015–2024. Samples have been collected in compliance with the requirements of State Standard R 59024-2020, State Standard 17.1.5.01-80, and State Standard 31339-2006. Identification of the hydrochemical and toxicologocal parameters of the water, bottom sediments and aquatic organisms has been conducted according to the provisions of the guidelines developed and adopted for the monitoring environmental surveys at the federal level. Results. Concentrations of biogenic elements and total mineralization of water were favorable for the vital activity of aquatic organisms. Water in the lower reaches of the Don River is characterized by a high trophic status. Local pollution of the investigated area with priority toxicants has been found. Conclusion. The water areas most polluted with petroleum products are the mouth of the Temernik River, the site of the Rostov-on-Don city sewage outlet, and the Mokraya Kalancha River Branch, where their threshold level in bottom sediments is exceeded by 9–25 times. Localized elevated concentrations of polychlorinated biphenyls and petroleum products in water, as well as benz(a)pyrene in bottom sediments, further worsen the environmental conditions for aquatic organisms. The quality of aquatic bioresources caught in the Don River has been found satisfactory in terms of pollution, and their consumption does not pose a danger to human health.
Keywords: Lower Don, hydrochemical regime, priority toxicants, water, bottom sediments, aquatic biological resources, anthropogenic influence, natural factors
Long-term dynamics of phosphorus concentration and assessment of eutrophication in the lower reaches of the Don River
Sorokina V.V., Kleshchenkov A.V., Gerasyuk V.S., Likhtanskaya N.V., Kulygin V.V., Gurtovaya T.Yu., Zhulidov A.V., Liu Maodian, Berdnikov S.V.
Abstract
Background. Excessive input of biogenic substances into surface waters poses an environmental problem. In the late 20th – early 21st centuries, biogenic load to rivers decreased due to activities related to water resource management (wastewater treatment, ban on the use of phosphate detergents, reduction in the use of some agricultural fertilizers, etc.). Relevance. Reliable data on phosphorus levels in water and their long-term dynamics in surface waters are scarce, mainly due to data quality issues. There is still little information on how the trophic status of the lower Don River has changed. The aim of this work is to conduct the comparative analysis of long-term (1986–2002 and 2011–2020) trends in changes of mineral and total phosphorus levels in the lower reaches of the Don River and to assess the related change in the probabilities of development of certain trophic conditions. Methods. This study has been carried out based on the data obtained through the analysis of phosphate and total phosphorus content in water in the outlet section of the Don River (stanitsa Razdorskaya) in 1986–2002 and 2011–2020 and the further statistical modeling using the WRTDS (Weighted Regressions on Time, Discharge, and Season) method. Results. Major trends in variation of the levels of phosphates and total phosphorus have been identified. The concentration of phosphates and total phosphorus shows negative dependence on water discharge. Since 1995, there has been a decreasing trend in the relative share of the mineral phosphorus component in total phosphorus and an increasing trend for the organic component. Based on the levels of total phosphorus in the water, the trophic status of the lower Don River has been defined for the period 1986–2020. The status of the lower Don River changed from mesotrophic in the 1990s to eutrophic in the first decade of the 21st century. In the second decade of the 21st century, a positive trend in phosphorus levels in the river water changed to a negative one, and in 2015, the eutrophic conditions shifted to mesotrophic. Conclusion. The mechanisms responsible for the observed long-term changes in phosphorus levels in the lower reaches of the Don River remain unclear and may be clarified by further studies. We believe that the observed long-term variations in phosphorus levels in the river water are related to drastic changes that have been occurring in agriculture, industry, and other economic activities since 1991. Changes in the hydrological regime (low river flow) have also contributed by affecting the qualitative characteristics of the runoff of biogenic elements and their ratios.
Keywords: mineral phosphorus, total phosphorus, river runoff, Don River, trophic conditions
Biology and Ecology of Aquatic Organisms
Dynamics of abundance and biomass of pontogammarus (Pontogammarus maeoticus Sowinsky, 1894) in the Eastern Azov Sea in the context of changing water salinity in 2001–2023
Saenko E.M., Kotov S.V.
Abstract
Background. The ongoing climatic changes have a significant impact on the fishing resources of the Azov Sea. Relevance. Due to the depressed state of the stocks of traditional fishing targets, it is urgent to search for alternative ones that can compensate for the shrinking catches and ensure the development of fishing in new environmental conditions. The aim of this work was to assess the abundance and biomass dynamics of the pontogammarus in the context of the increasing salinity. Methods. This work is based on the data collected over the course of the 2001–2023 studies on the assessment of the abundance and biomass of the pontogammarus population in the Azov Sea, taking into account the habitat parameters (namely, salinity). The pontogammarus samples were collected in the supralittoral zone with a benthic frame and a sampling trap, and in the upper sublittoral zone at a depth of 0.5 m with a trap. The samples were fixed with 4 % aqueous formaldehyde solution. The laboratory processing included the determination of the species, sex, dimensional characteristics, the number of individuals in the sample, and the individual weight of the crustaceans. Results. In 2001–2015, within the salinity range of 9.64– 13.24 ‰, an increase in the specific abundance and biomass of the population was recorded in the Azov Sea. A significant positive relationship was found between the specific abundance, specific biomass and salinity of the sea (r=0.87–0.91). A further increase in the salinity to 14.91–15.29 ‰ in 2021–2023 had an adverse effect on the density of crustacean distribution as compared to that in 2015. Correlation analysis revealed a strong negative relationship (r=-0.99) between the salinity and the number of crustaceans in the aggregations, as well as their biomass. In Taganrog Bay, at a salinity of 5.26–7.34 ‰, the abundance and biomass had the lowest values compared to the entire area of the Azov Sea. With the increase in the salinity in 2009–2015, there was also recorded an increase in the specific abundance and biomass of the pontogammarus. A strong positive relationship (r=0.90–0.92) was identified between quantitative indicators of population distribution and water salinity. In subsequent years (2021–2023), the relationship between the quantitative characteristics of the pontogammarus population and the salinity in the bay remained positive. Conclusion. The water salinity in the range of 11.25–13.24 ‰ is optimal for the vital activity of pontogammarus; it is the level at which the aggregations with the highest abundance and biomass can be formed. If the water salinity of the Azov Sea continues to increase, in the following years, a decrease in the abundance and biomass of crustacean aggregations is expected, which will lead to the reduction in the total stock of this exploitable resource.
Keywords: pontogammarus, salinity, Azov Sea, distribution, abundance, biomass, stock
Morphometric features of the branchiopod belonging to Artemia Leach, 1819 genus in Sivash Bay
Semik A.M., Zamyatina E.A.
Abstract
Background. The increase in the catch volumes of Artemia (brine shrimp) in the 21st century exacerbated the need for development of the measures for conservation and rational exploitation of this valuable aquatic living resource. Relevance. The Republic of Crimea, due to the favorable environment in Sivash Bay, is in possession of considerable Artemia stocks. The variation in the water and salinity regime of Sivash Bay over the last decades necessitates a thorough examination of the biology of these crustaceans in the changing environment, as well as investigation of their morphometric characteristics. The aim of this study is to investigate the morphometric parameters of the brachiopod brine shrimp (Artemia Leach, 1819) of Sivash Bay. Methods. A correlation analysis of the morphometric parameters (9 morphological characters and 3 meristic characters) of Artemia males and females has been conducted. Collection and laboratory processing of the hydrobiological samples have been carried out following the standard practices. For plankton sampling, the Apstein plankton net has been used. Water salinity has been identified with refractometric salinometer, and water temperature has been measured with Kelilong thermometer. The samples have been fixed with 4 % formaldehyde; their laboratory processing has been conducted using a stereoscopic microscope; the weight of the investigated organisms has been measured with analytical balances accurate to 0.0001 g. Results. Water and salinity regime of some Sivash Bay areas has been identified; it is found to be determined by the geographical features of the bay and seasonal precipitation. Geographically, the water salinity increases from east to west in the Western Sivash Bay and from north to south in the Eastern Sivash Bay. In Sivash Bay, both parthenogenetic and bisexual populations of brine shrimp have been identified. The female individuals are characterized by a greater body length as compared to the male ones. The furcal values in the females and the abdominal values in the males have been found to be the most variable parameters. Conclusion. Comparative analysis of the morphometric parameters in the mature Artemia individuals has shown their dissimilarity for males and females. The normal distribution has been recorded for the total body length (tl) and the abdomen length (al), the head capsule width (hw), the eye diameter (ed), and the cephalothorax length (cl), while the bimodal distribution has been recorded for the furca length (fl), the relation of the furca length to the abdomen length (fl/al), and the relation of the cephalothorax length to the abdomen length (cl/al). No relation has been found for the abdomen length and the abdomen width in females (r=0.01); the relation of the abdomen length to the total body length shows strong correlation (r=-0.97). In females, contingency of the morphometric parameters was strong in 25.7 % out of all compared pairs; it was average in 18.2 % of cases, weak in 45.5 %, and absent in 10.6 %. In males, it was strong in 39.4 % out of all compared pairs, average in 31.8 %, weak in 9.1 %, and absent in 19.7 %.
Keywords: Sivash Bay, Artemia, morphometrics, parthenogenetic population, bisexual population, correlation analysis
Ichthyofauna of Marine and Inland Water Bodies
Influence of nanoparticles of industrial plastics on model fi sh Danio rerio (Hamilton, 1822)
Annenkov V.V., Palshin V.A., Lunina N.A., Danilovtseva E.N., Zelinskiy S.N., Kostrov S.V., Safi na D.R.
Abstract
Background. Nanoparticles of industrial plastics are considered as potentially hazardous contaminants of water bodies due to their ability to penetrate living cells by endocytosis. Relevance. Study of the effects of nanoplastics on hydrobionts at concentrations expected for natural waters is crucial for the implementation of environmental protection measures in the context of societal industrial development. Aim. In this work, the effect of polystyrene, polyvinyl chloride and polymethyl methacrylate nanoparticles on a model organism—fish Danio rerio (Hamilton, 1822)—has been studied. Methods. Fluorescent nanoparticles with a diameter of 110–180 nm were used; their dispersions did not contain toxic stabilizers and preservatives. Cultivation in the presence of nanoplastic was carried out starting from the second day after fertilization for 20–30 days at high (1–15 mg/L) and three months at low (0.01–0.1 mg/L) concentrations. Results. Nanoparticles were found to have no significant effect on embryo and fry survival at concentrations of 0.01–0.1 mg/L, which exceeds the expected presence of nanoplastic in natural waters. At higher concentrations (5–15 mg/L), survival rates decreased. The use of fluorescent nanoparticles showed that plastic is ingested by fish through food sources capable of assimilating nanoparticles (infusoria), and when their feed is replaced by larger organisms (nauplii), the fish are cleared of nanoplastic. Adult fish surviving influence of nanoplastic are able to reproduce at the level of control groups, and in case of exposure to high concentration of polymer (15 mg/L) there are no abnormalities in embryo development, in contrast to the individuals in the control groups. It can be assumed that the high concentration of nanoplastic acts as a selection factor, reducing the proportion of individuals with genetic abnormalities, although this hypothesis needs careful testing using molecular genetics and biochemical methods. Conclusion. The results obtained indicate that there is no significant effect of nanoplastics on D. rerio at possible natural concentrations; these results can be used to develop methodological approaches to studying the effects of nanoplastics on other organisms, including commercial fish.
Keywords: Danio rerio, zebrafi sh, nanoplastic, fl uorescence, toxicity
On the capture of the silver-cheeked toadfi sh Lagocephalus sceleratus (Gmelin, 1789) in the Kerch–Taman region of the Black Sea
Dudkin S.I.
Abstract
Background. Due to the climate change (global warming) and expansion of maritime shipping routes in the Black Sea, new fish species migrating from the Mediterranean Sea and the seas of the Northwest Indian Ocean are regularly recorded. Relevance. New invasive fish species claim the Black Sea area and act as trophic competitors or predators toward the native species; they also may pose a danger to humans. The aim of this work is to describe the cases of the silver-cheeked toadfish capture in the Kerch– Taman region of the Black Sea in the spring of 2024, to characterize its biological features and possible migration routes in the Black Sea, and to provide information on the possible danger of its consumption by humans and pets. Methods. Information about the cases of the silver-cheeked toadfish capture has been obtained from oral reports of spearfishers and upon the analysis of photographic evidence. Results. Two cases of the silver-cheeked toadfish capture have been confirmed for the depths down to 8 m on sandy bottoms near Volna (Wave) and Veselovka villages of the Temryuk District of the Krasnodar Territory in the spring season of 2024. They are the first confirmed cases of its capture in the Kerch–Taman region of the Black Sea. Conclusion. Finding of the large mature individuals of the silver-cheeked toadfish in the Northeastern Black Sea in spring serves as a potential evidence of its reproduction during the summer season and formation of its local seasonal populations, as well as the possibility of its wintering in some areas of the Southeastern Black Sea. This species is highly poisonous to humans upon consumption due to the high content of tetrodotoxin in tissues, including muscles.
Keywords: Black Sea, Kerch–Taman region, silver-cheeked toadfi sh, Lagocephalus sceleratus, invasion
Aquaculture and Methods of Artifi cial Reproduction
On the ecological state of the spawning grounds of the Yeysk Experimental Hatchery in 2020–2023
Poroshina E.A., Sergeeva S.G., Belousov V.N., Gorbenko E.V., Bugaev L.A.
Abstract
Background. The Yeysk Experimental Hatchery was created for the reproduction of zander and roach— aquatic biological resources of the Azov Sea Basin. In recent years, a decrease in its efficiency has been observed. Relevance. Results of the analysis of the ecological state of the Yeysk Experimental Hatchery spawning grounds will provide the basis for development and adjustment of the measures aimed at the facilitation of the artificial reproduction of zander and roach compliant with the relevant data. The aim of this work is to assess the ecological status of the spawning grounds and to determine the causes of the decrease in the number of released juveniles. Methods. The morphobiological characteristics of the individuals belonging to the investigated species and the hydrological and hydrochemical regime in the water bodies comprising the hatchery have been studied according to the methods generally accepted in the field. Results. In 2020, in the context of the freshwater runoff shortage and high water salinity at the spawning grounds (up to 10 ‰), the number of the released zander and roach juveniles decreased by 9 and 3 times, respectively, as compared with the average annual data. In 2021, resulting from an adverse hydrological situation, the water bodies where spawning, hatching, and growth of juveniles occurred were left dry for the summer season. In 2022, the hydrological and hydrochemical conditions improved, yet the number of the released juveniles remained at an extremely low level, and in 2023, during the surveys in June–August, roach juveniles were completely absent in catches, and zander juveniles were very scarce. Zander and roach breeders entering for spawning were characterized by low values of the morphobiological parameters (weight, length, fecundity, condition factor, and gonadosomatic index). Conclusion. Negative environmental conditions observed in the Yeysk Experimental Hatchery in 2020–2023 affected spawning, timing of the juvenile migration into the sea, and the number and quality of juvenile zander and roach.
Keywords: Yeysk Experimental Hatchery, zander Sander lucioperca, roach Rutilus rutilus, hydrological and hydrochemical conditions, age composition, fecundity, physiological state, juvenile fish.