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Dépôts récents
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On the development of Azov sturgeon breeding on the occasion of the 150th anniversary of sturgeon culture in RussiaВодные биоресурсы и среда обитанияThis article presents a retrospective review of sturgeon breeding evolvement in the Azov Sea Basin. A particular emphasis is placed on the research covering breeders and rearing of juveniles; the development of efficient long-term practice of their culture has been a subject of the institute's research for many years. The best practices of using the individuals at different points of their spawning run (autumn, spring, summer) and different places of capture along their spawning migration route (Taganrog Bay, river deltas, dam-adjacent sites) for breeding purposes in culture have been identified for each species (great sturgeon (beluga), Russian sturgeon, stellate sturgeon) stage by stage on the basis of morphophysiological investigation of heterogeneous individuals belonging to each investigated group of breeders. Special attention was paid to gonad maturity stages in females, and receptivity of oocytes to fertilization. The reasons for the current low recruitment to the stocks of sturgeon species from cultivated generations have been identified; they include reproductive potential of the females from a farmed broodstock and the state of sturgeon hatcheries that calls for an update of their technical equipment and facilities. It is obvious that the Azov sturgeon stock enhancement cannot be steered out of this crisis without the government support, neither at present, nor prospectively. This article also names the most outstanding researchers in sturgeon breeding (biologists, physiologists, fish farmers), who played an important role in the development of the Azov sturgeon culture.
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Investigation of microbiological indicators of calcium food additive derived from veined rapa whelk Rapana venosa shellsВодные биоресурсы и среда обитанияThe relevance of this research is conditioned by the absence of industrial utilization of the waste discarded while processing the veined rapa whelk (shells), despite the fact that this mullusc is caught in the Azov and Black Sea Fishery Basin annually. As a result of processing 2,746.1 tonnes of rapa whelk caught in the Azov Sea in 2019, almost 2,000 tonnes of shells were derived. The microbiological safety indicators of the calcium feed additive derived from veined rapa whelk have been investigated, which was necessitated by the parts of mollusc viscera remaining in 50 % of shell cones after their processing. Samples of the calcium feed additive were prepared in 5 ways, differing in temperature (20, 80, 105 °C) and duration of drying (12 and 24 hrs, 3 and 9 months), as well as the presence/absence of viscera remains. The total bacterial load in all samples did not exceed the established norms (no more than 5×105 CFU/g); E. coli bacteria, Staphylococcus aureus and pathogenic microorganisms, including salmonella, have not been detected. Thus, the investigated methods of calcium feed additive production can be considered as alternative ones, ensuring the microbiological safety of this type of product with a shelf life of at least 3 months, while in paper bags.
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Revision of standardization documents on air-dried fish to ensure their compliance with the requirements of TR EAEU 040/2016Водные биоресурсы и среда обитанияFish products, obtained through curing, drying and dry-curing processes, are in great demand among the population and represent a ready-to-eat food item. This article presents a comparative analysis of the requirements of TR EAEU (Technical Regulation of the Eurasian Economic Union) 040/2016 and standardization documents to the moisture content in cured, dried, dry-cured and air-dried fish; inconsistency in these requirements, which should be eliminated during revision of the specifications for the indicated types of products, is identified. Results of the investigation of moisture content, conducted on samples of the cured and air-dried fish distributed through a market chain, are presented; they have shown that the major part of the investigated products did not meet the norms of moisture content, prescribed by the standards. For this reason, labeling of these products can be viewed as misleading in terms of complete and accurate information on a food item. Another requirement of TR EAEU 040/2016 to the cured and air-dried fish - presence of the characteristics of an ripened product - has also been analyzed. This article points out that the standardization documents do not provide biochemical indicators that could make it possible to evaluate the process of ripening in cured and air-dried fish; ripening characteristics are conveyed verbally along with the description of organoleptic properties. In terms of buffer value, investigation of the ripening level of cured and air-dried fish, distributed through a market chain, has shown it to be low for the products derived from lookdown, Black Sea horse mackerel, goby, Atlantic mackerel, and Atlantic herring, as compared to cured and air-dried Caspian roach. This article indicates that the presence of characteristics of ripened products cannot include all fish species used for production of cured and air-dried fish. Results of the conducted analysis have been used in development of the international standard for air-dried fish.
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Prospective uses of the macrophyte storm debris in the wrack zone of the Azov and Black Sea Fishery Basin (review)Водные биоресурсы и среда обитанияMass aggregations of brown algae Cystoseira and seagrass Zostera (eelgrass), which are formed along the wrack line during storms and natural exfoliation, can be considered one of the underexploited primary resources of the Azov and Black Sea Fishery Basin. As a rule, the process of their aggregation falls on the summer - autumn season, which coincides with the high season, leading to people's discomfort during their recreation time. Therefore, the issue of the prospective utilization of algae storm debris, its harvesting and primary processing can be deemed quite vital. The investigated macrophytes, washed ashore during storms or seasonally, are the source of valuable materials; Zostera provides zosterin and fiber, and Cystoseira is rich in alginic acid, iodine and selenium. This article considers proven methods of algae processing for nutritional purposes, obtaining dietary supplements and cosmetic products, in paper manufacturing, and the use of macrophytes as fertilizers and animal fodder. The methods of primary processing, entailing the best possible preservation of quality of the investigated algae and involving the processes of drying, freezing and chemical treatment, are studied. Specifics of algae storm debris collection and the necessity of timely removal of macrophytes from sandy coastline are indicated. Recommendations on natural and artificial drying, freezing and salting of macrophytes are given.
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Morphological features of oogenesis of the Pacific oyster (Crassostrea gigas, Thunberg) introduced into the Black SeaВодные биоресурсы и среда обитанияMorphological features of the Pacific oyster (Crassostrea gigas, Thunberg) oogenesis in the course of two-year cultivation cycle in Donuzlav Liman have been studied. The data on morphophysiological characteristics of this species (diameter and volume of acini, oocytes, nuclei, nucleoli, as well as the nucleoplasmic index) are given for different seasons. Quantitative changes in the size of oocytes (D) are presented in relation to water temperature (T, °С), which is described by the logistic function equation. It is shown that the dynamics of oogonia number (Nо) is linked to water temperature (T) with an inverse relation and is described by an exponential equation. The synchronicity of the changes in volumes of acini, oocytes and cell nuclei in the course of the reproductive cycle is shown, as well as the interrelationship between the volumes of these components. There was found to exist an asynchronicity in nuclei functioning and the nucleoplasmic index in the process of reproduction, which is linked with the synthesis of ribosomal proteins. Following the obtained data, 1-to-6 score of the maturity stages for the Pacific oyster females in the course of annual reproductive cycle is presented: passive state; beginning of oogenesis; active oogenesis; pre-spawning state; maturation and spawning; post-spawning transformation. The months, during which each maturity stage was the most prevalent, are given.
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Phytoplankton-based biomonitoring in assessing the pollution level of a lentic freshwater body in Hooghly District, West Bengal, IndiaВодные биоресурсы и среда обитанияPhytoplankton is the base of every aquatic food web. During the assessment of the trophic status of the investigated lentic water body (within Lake City Housing Complex, Mankundu, Hooghly, West Bengal, India), phytoplankton composition and its temporal variation are proved to be the most important. In this study, 30 phytoplankton taxa have been recorded in various arrangements throughout the season. The maximum number of phytoplankton species with the highest Shannon–Weaver diversity index value represented the pre-monsoon season, whereas the least number of phytoplankton taxa and the lowest diversity indicators characterized the post-monsoon season. The development of algal bloom by one specific taxon, Botryococcus braunii, in the postmonsoon season indicates the change in the trophic status of this particular water body. As a criterion for the beginning of the algal bloom, an exceedance of 1 mg/L in nitrate concentration can be considered. The phytoplankton composition, values of various diversity indices, its density and species distribution pattern, and selected environmental parameters have been investigated, as well as the results of the analysis of rank abundance curves, which allowed for evaluation of the ecological status of this lentic water body. This study describes the change or shift in the ecosystem of the investigated water body towards eutrophication and establishes its pollution level as moderate to light.
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Scientific, Technical and Economic Committee for Fisheries (STECF) – 72nd Plenary report (STECF-PLEN-23-01)The JRC presented a brief review of the current STECF system in place to provide advice on Mediterranean fisheries management and data collection issues. JRC highlighted some structural risks and inefficiencies that currently exist. The review explored some examples of integrated actions that could reduce or mitigate such risks. Such actions as part of a long-term strategy would lead to a proactive advisory process as opposed to the current more reactive sequence of individual steps considered by STECF. STECF notes this initiative from the JRC and aims to revisit the topic in time for development of the next management plan stage, post 2025. On 21 February 2023, the Commission adopted the Fisheries and Ocean package consisting of four documents: the Communication on the functioning of the CFP, the Action Plan “Protecting and restoring marine ecosystems for sustainable and resilient fisheries”, the Energy transition initiative and the report on the functioning of the Common Market Organisation (CMO). The package brings together all different aspects of the EU’s policy on fisheries and the Ocean, looking at the future, and at how we can ensure that fisheries continue to grow in resilience and sustainability. With this package, the European Commission plans on launching a policy discussion with all institutions and stakeholders the EU’s policy on fisheries and the Ocean
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Scientific, Technical and Economic Committee for Fisheries (STECF), Monitoring of the performance of the Common Fisheries Policy (STECF-adhoc-23-01)Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. This report deals with the monitoring of the performance of the Common Fisheries Policy.
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Experimental evaluation of toxic resistance of benthic microalgae Thalassiosira excentrica Cleve 1903 (Bacillariophyta) under the copper ions impactVestnik of MSTUWith an increase in anthropogenic pressure on the ecosystem of the coastal zones of the sea, the relevance of assessing the state of plankton and benthos communities also increases. In the course of the study, the dynamics of the number of cells of the clone culture Thalassiosira excentrica Cleve 1903 (Bacillariophyta) has been determined under the influence of CuSO4·5H2O of various concentrations (32–1024 µg·L–1) under the conditions of 10-day experiments. In the control and at a low concentration of Cu2+, the proportion of living cells remains almost unchanged. The threshold concentration of copper ions for the survival of T. excentrica is 128 µg·L–1. At higher concentrations of Cu2+ (256–1024 µg·L–1), a sharp inhibition and death of the culture has been noted already within 1–3 days. The increase in the absolute number of cells at low concentrations of copper (32–64 µg·L–1) is described by the sigmoid response curve of the test-object. The growth values increase by 4–8 times on the 1st–5th day and decrease by 25–30 % by the 10th day. At Cu2+ concentrations of 128–256 µg·L–1, there is no positive increase in the number of cells on days 1–5; on subsequent days, it decreases by 2 times or drops to zero. The intensity of the specific cell growth significantly decreases depending on the increase in the concentration of the toxicant. It has been found that on days 1–5, the specific increase is positive in the range of copper concentrations of 32–128 µg·L–1 and negative – at concentrations of 256 µg·L–1 and higher. In the period of 5–10 days, for all concentrations of the toxicant, the values of the specific increase are negative. The obtained results make it possible to recommend T. excentrica as a promising test object for toxicological experiments.
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Taxocene of polychaeta of the Laspi Bay water area (the Crimea, Black Sea)Vestnik of MSTUThe coastal zone of Laspi Bay (the Crimea, Black Sea) is attractive for the development of recreational activities. It can negatively affect the state of the bay ecosystem and adjacent waters. The aim of this study is to assess the current state of polychaetes inhabiting the loose soils of the littoral and sublittoral areas of Laspi Bay. In 2016–2019 the fauna of polychaetes was studied in the waters of Laspi Bay. Macrozoobenthos were collected on cruises 84, 86, 96, 108 aboard the research vessel Professor Vodyanitsky and in coastal expeditions. 89 samples were taken (19 deep-water, 70 coastal). 45 species of polychaetes were identified. The average abundance of Polychaeta was 2 368 ± 467 ind./m2. The average biomass was 44,128 ± 13,919 g/m2. Terebellides stroemii makes a significant contribution to the formation of these indicators. The ranked series by density index is headed by T. stroemii, Nephtys hombergii and Melinna palmata. The largest abundance of species is noted at a depth of 46 m where the soil is represented by sand and pebbles. The highest number is noted at depths of 93.5–98 m. Prionospio сirrifera makes the main contribution to the total number. The highest biomass is noted at depths of 53.5–58 m. T. stroemii makes the main contribution to the total biomass. In the Laspi Bay waters are recorded characteristic species – P. сirrifera and Micronephthys longicornis. They are found both in shallow waters and at great depths. Rare species found only at one station include 18 polychaete species. The results obtained give an idea of the taxonomic composition of polychaete worms in the waters of Laspi Bay and can be useful for further monitoring of this area.
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Programming of marine engineers' simulator trainingVestnik of MSTUContinuous improvement of the technical equipment of sea vessels is inevitably accompanied by the development and complication of the training base for marine specialists. Simulator training based on a computer model of operating the units of the liquefied natural gas tanker of the Veliky Novgorod type includes interactive computer programs for learning management, created using the e-Tutor computer module included in the simulator delivery set. In the course of systematizing the experience of using specialized programming tools for educational and research activities of students in organizing and conducting simulator training for electrical engineers on computer simulation models of sea vessels, a system of conventional graphic symbols for the elements of the flowchart of the training exercise program has been formed and their description has been given. Training and control exercises include familiarization with the mnemonic diagrams of the integrated marine vessel automation system and assessment of the state of the ship's electrical power system with their help, starting the propulsion electrical installation, providing energy to the operating propulsion electrical installation under load changes, switching on the backup diesel generator unit for parallel operation with the network in normal and emergency modes, acceleration of the vessel to the given speed in accordance with the tasks of the instructor. The advantages of training programming using the e-Tutor computer module are the ability to use the simulator in self-study mode with automated teaching support.
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Features of ensuring high-quality work of modern electrical power systems of unmanned vesselsVestnik of MSTUUnmanned seagoing vessels are increasingly being used. In the paper the dump scow Rabochaya is considered as an example of an unmanned vessel. An extended marine control system, a video surveillance subsystem, a surveillance and search engine are additionally installed on the scow to carry out industrial tasks in unmanned mode. The correct operation of these systems and the whole vessel depends on the high-quality operation of the ship's electrical power system. The aim of the study is to identify abnormal modes of parallel operation of marine diesel generator sets and to develop methods and means for their elimination. The results of the experimental research and mathematical modeling have revealed the existence of power exchange oscillations when the ship generators operating in parallel. Power exchange oscillations can be detected with the help of generator current oscillations. It has been proposed to introduce a unit for eliminating power exchange oscillations (EPEO) into the automatic control system of ship electrical power systems for eliminating such oscillations. An algorithm for the operation of the EPEO unit has been developed, it controls the settings of the rotational speed regulators of diesel-generator sets. The proposed methods and tools reduce the amplitude of power exchange oscillations to an acceptable value, and therefore contribute to the high-quality operation of the ship's electrical power system and control systems in unmanned mode. The results obtained make it possible to ensure reliable and trouble-free operation of any autonomous electrical power system during the operation mode without maintenance personnel.
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Application of the proportional navigation method in solving problems of navigationVestnik of MSTUThe development of methods and algorithms for ship control when maneuvering relative to a moving object and the creation of automated control systems based on these developments is an urgent task of navigation. The most optimal way to implement control of a moving object relative to another moving object is based on using the proportional navigation method. As applied to navigation problems, this method has been studied at the level of describing the kinematics of the movement of two points. The mathematical model provides for a preliminary calculation of the extrapolated ship coordinates. The construction of ship motion trajectories for any given proportionality factor is carried out taking into account the dynamics of the ship and makes it possible to obtain the law of rudder shift, as well as to predict changes in the process of maneuvering such ship parameters as angular velocity and drift angle. The proposed mathematical model can be used for algorithmic and software support for automated ship control systems when maneuvering relative to a moving object.
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Black Sea–Caspian sprat (tyulka) industrial fishing in the Azov Sea: Presently used fisning gear, methods, and its current trendsВодные биоресурсы и среда обитанияThis paper presents the main fishing methods and gears previously used or appraised and currently applied in the course of Black Sea–Caspian sprat (tyulka) fishing in the Azov Sea: their performance, merits and demerits. Black Sea–Caspian sprat (tyulka) fishing comprises the coastal fishing with pound nets and the fishing off the board of fishing vessels with purse seines ans midwater trawls. Recently, sprat catches with pound nets have been on the decline; meanwhile, use of fishing vessels, albeit more resource-consuming and dependent on the multitude of factors, can prospectively be more productive than the coastal fishing, even though currently it shows lower catches. A brief characterization of the Black Sea–Caspian sprat (tyulka) industrial fishing in the recent years is given, its trends and challenges are discussed. Daily vessel reports have been processed for 2015–2021, and the comparative data on the operation of the vessels of various types are presented; the trends in the changing industrial fishing parameters during the investigated period show a considerable decrease in all the parameters. Another crucial issue is the necessity to reduce the by-catch of non-target fish species (sturgeons, Black Sea turbot) in long-continued depressed state with midwater trawls. The presented data will allow for the current status assessment of the Black Sea–Caspian sprat (tyulka) industrial fishing and envisioning the efficient, yet selective and environmentally sound fishing methods to be developed and revised.
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Catch composition of the European anchovy (Engraulis encrasicolus L., 1758), wintering off the coast of Abkhazia in the 2021/2022 fishing seasonВодные биоресурсы и среда обитанияBased on the available data for the 2021/2022 fishing season, the ecological structure and fishing biological parameters of the European anchovy (E. encrasicolus L., 1758), wintering in the coastal waters of Abkhazia, have been analyzed. This paper presents materials that make it possible to analyze the dynamic parameters of the Azov and Black Sea stocks of the European anchovy aggregating off the coast of Abkhazia in the winter season. A comparative analysis of the main biometric parameters has been carried out. For data analysis, well-established ichthyological methods have been used. The available data on the European anchovy (both Black Sea and Azov Sea forms) caught during the investigated period characterize the dynamics of the length–age catch composition and are indicative of its intra-annual fishing patterns. Changes in the population characteristics present in the catch composition as compared with the previous years have been identified. The absolute catch values and their fluctuations are presented by the month. Analysis of the available material has indicated the main dynamic changes that characterize the wintering anchovy population as stable with a tendency for its total biomass development on a moderate level, which is not conducive for increasing the fishing effort in the next 1–2 years.
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Transformation of the polychaete taxocene in the shallow part of Karkinit Bay under conditions of changing salinityВодные биоресурсы и среда обитанияKarkinit Bay is the largest bay of the Black Sea. Since the 1960s, after the construction of the North Crimean Canal, the water in the top of the bay was heavily desalinated by runoff from fish ponds and irrigation systems. In 2014, after the canal was blocked, the salinity of the water increased, and the living conditions of the organisms changed. This work is aimed at the assessment of the change in the species composition and quantitative characteristics of the polychaete taxocene in the shallow zone of Karkinit Bay in 2018, which resulted from the changes in water salinity, as compared to those in 2008. The studies were carried out in August of 2008 and 2018—in three sampling areas at 17 stations (in 2008 and 2018 alike) at depths of 0.2–1.7 m. Samples of macrozoobenthos were collected using a manual bottom grab with a sample area of 0.04 m2. In the top part of Karkinit Bay in the first half of the 21st century, 35 species of polychaetes were recorded. Polychaete worms belonging to 19 families have been identified, with the families Phyllodocidae, Syllidae, Nereidae, and Spionidae comprising the largest number of species (4 species each). Three species — Lysidice unicornis, Polyophthalmus pictus, Syllis prolifera — were recorded in Karkinit Bay for the first time. It is shown that, with the post-2014 increase in salinity, the species richness of the polychaete taxocene in the investigated area has also increased. In 2008, 24 species were found, and in 2018, 32 species. The average abundance of polychaetes in 2008 was 948± 345 ind./m2, and in 2018, it was 417±161 ind./m2. Hediste diversicolor reached the highest abundance in 2008 (average abundance 676±371 ind./m2, maximum abundance 2313 ind./m2). In 2018, Polydora cornuta (600 ind./m2), Platynereis dumerilii (225 ind./m2), and Scolelepis tridentata (450 ind./m2) were characterized by the highest abundance. With an increase in salinity in the range of 1.5–17.8 ‰, a decrease in the density of H. diversicolor was recorded and, conversely, an increase in the density of other Polychaeta species.
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Evaluation of the tolerance threshold of marine benthic diatom Pleurosigma aestuarii (Bréb. in Kütz.) W. Smith, 1853 (Bacillariophyta) under the impact of copper (II) ionsВодные биоресурсы и среда обитанияCopper compounds accumulate in marine bottom sediments as the result of human activity and, being highly toxic, affect microphytobenthos. Evaluation of the tolerance ranges of benthic diatoms to copper pollution is important for biotesting and assessment of coastal marine environment. This work is aimed to reveal the dynamics of growth and cell death of marine benthic diatom Pleurosigma aestuarii (Bréb. in Kütz.) W. Smith, 1853 under the impact of a wide range of copper (II) ions concentrations over the course of a 10-day experiment in clonal culture, as well as to identify a tolerance threshold for this species, critical for its survival when exposed to the toxicant. The study has focused on assessment of the changes in the proportion (%) of alive cells, absolute cell number and specific growth rate of the culture at different exposure durations and concentrations of Cu2+ ions (32–1024 μg/L) and was meant to evaluate the applicability of this species as a new test object for ecotoxicology. In the control culture and in the cultures exposed to Cu2+ in the range of concentrations 32–256 μg/L, the proportion of alive cells did not change over the course of the experiment (95–99 %). At Cu2+ concentration 320 μg/L, the proportion of alive cells decreased to 23 % on the 3rd day and to 10 % on the 5th day, which provided a basis to consider this value as a threshold one for P. aestuarii survival. At Cu2+ concentrations 384 μg/L and higher, up to the maximum one (1024 μg/L), drastic inhibition of the culture was recorded as early as on the 1st day, and on the days 3–5, all the cells died. The increase in the absolute cell number in the concentration range 32–256 μg/L was consistent with the dose–response sigmoid model. Over the timespan of days 1–7, the cell number increased by 3–5 times, reaching its maximum, and then it decreased by 10–12 % by the 10th day. At Cu2+ concentrations 320 μg/L and higher, the increase in the cell number was strongly suppressed since the 1st day. Within the 32–256 μg/L range, the test culture is characterized by positive specific cell growth rate for the period up to 7 days; at the threshold concentration 320 µg/L and higher, this test parameter becomes negative. Thus, P. aestuarii should be recommended as a new appropriate test object both for toxicological experiments and for monitoring of coastal marine environment affected by technogenic pollution.
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Polychaeta taxocene in the coastal area of Lake DonuzlavВодные биоресурсы и среда обитанияThis work is based on the data collected during the benthic survey of soft sediments in the coastal area of Lake Donuzlav conducted in August, 2020. The current status of the species composition of polychaetes in Lake Donuzlav was investigated. The samples were collected using a manually operated grab sampler with a capture area of 0.04 m2 at the depths from 1 to 8 m. The following indicators were used to describe the quantitative development of benthos: abundance, biomass, occurrence, density index, and Czekanowski–Sørensen index. A total of 31 species of polychaetes have been found. The average values of polychaetes abundance and biomass in the investigated area were 239±51 ind./m2 and 1.537±0.599 g/m2, respectively. The main contribution to the total abundance is made by Spio decorata, and to the total biomass by Lagis neapolitana. The largest number of species and the highest abundance were recorded at the depths of 1.1–2 m. The largest biomass was recorded at the depths of 6.1–7 m. The ranked series according to the density index is headed by L. neapolitana, Glycera tridactyla, and S. decorata. The trophic structure of polychaetes is represented by poly-, phyto-, detritophages, carnivores, and the animals, the food spectrum of which has not been studied. The most widely represented group is carnivores; it comprises 10 species of polychaetes. The least number of species (1) was recorded for phytophages. Over 1990–2020, 73 species of polychaetes were identified; they belonged to 29 families and 56 genera.
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Specific features of spatial distribution of hydrochemical parameters in the Curonian Lagoon of the Baltic Sea in 2018–2022Водные биоресурсы и среда обитанияCuronian Bay of the Baltic Sea is a lagoon that is considered to be a water body of the highest fisheries importance. Its current geoenvironmental status is characterized by a number of problems: influx of biogenic substances from a large catchment area, algal bloom, etc. As part of the monitoring surveys of the habitat of aquatic living resources that were conducted in Russian waters of Curonian Lagoon in 2018–2022, the spatial distribution of hydrochemical parameters was investigated in 6 areas established on the basis of their morphometric and hydrological features: Teply (Warm) Bay, western, central, eastern, and southern areas, and the Neman River discharge zone. Hydrochemical conditions in Teply Bay were characterized by a considerable deviation of dissolved oxygen concentrations from the rest of Russian waters of Curonian Lagoon, as well as by the higher values of BOD5 and ammonia nitrogen, and lower values of pH and nitrate nitrogen. In the western area, the lowest content of dissolved oxygen, BOD5, ammonia, and nitrate nitrogen was recorded. In the southern area, there was a reduced content of ammonia nitrogen and nitrate nitrogen. In the central area, the values of hydrochemical parameters were close to the average ones for Russian waters. The eastern and Neman River discharge areas, exposed to significant influence of the Neman River runoff, were characterized by a high concentration of nitrate nitrogen during seasonal flood, as well as by increased values of ammonia nitrogen and BOD5 during algal bloom in summer.
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The influence of water salinity on generation of near-bottom hypoxic phenomena and the level of primary production of organic matter in Taganrog BayВодные биоресурсы и среда обитанияAt present, the Azov Sea ecosystem exists in the context of continuously decreasing continental runoff and increasing water salinity, which reached in 2020–2021 the highest values for the entire period of observations since 1962. The increase in water salinity inevitably leads to the transformation in the composition of biological communities, which has a pronounced effect on the environment and fisheries. This paper discusses the long-term impact of water salinity on the development of near-bottom hypoxic phenomena and on the volume of primary production of organic matter by phytoplankton in Taganrog Bay during the summer season (1962–2021). A statistical ecosystem analysis describing the contribution of the major hydrological and hydrochemical factors into the processes of hypoxia formation in the bottom water layer of Taganrog Bay has been performed. It is shown that the desalinization of the waters of Taganrog Bay in 1993–2008 was accompanied by the increase in the size of hypoxic zones in the bottom water layer. During the modern period of salinization extending from 2009 to the present, there has been recorded a decrease in the scale of oxygen deficiency in Taganrog Bay. The most crucial contribution to the hypoxic processes in Taganrog Bay is provided by the stability of water masses, water temperature, organic nitrogen concentration, and the water salinity (due to the effect of salinity on the stability of water masses). During the streaks of Taganrog Bay salinization, the decrease in the stability of water masses and in the content of organic nitrogen and phosphorus in the water (crucial factors in the formation of hypoxic zones) has been recorded. The highest rates of the primary production of organic matter by phytoplankton in Taganrog Bay were observed during the desalinization period of 1962–1968, and the lowest ones were recorded during the salinization periods. The results of this assessment have exposed the significant relationship: the primary production of organic matter depends on the average annual runoff of the Don River, the water salinity, and the concentration of mineral nitrogen.
