Volga Delta Research Articles

Alien species of Poaceae Barnhart family in communities of South-East Europe saline soils

The paper considers the introduction of alien species of Poaceae Barnhart family into plant communities of South-East Europe salted habitats. In the region only two cosmopolitan alien members of this family - Echinochloa crus-galli (L.) P. Beauv. (archaeophyte of South Asian origin, ksenophyte, epecophyte) and Setaria pumila (Poir.) Roem. et Schult. (archaeophyte of East Asian origin, ksenophyte, epecophyte) - are registered on the specified ecotope type, but very limited both synthaxonomically (number of lower units) and geographically (only in the Lower Volga region - the Volga Delta and the south of Volga-Akhtuba flood-plain). Echinochloa crus-galli invades on saline habitats most actively, in some communities it can be both a constant and a rather abundant species but, most likely, is able to influence significantly the formation of only individual coenoses of a number of associations. Both species are registered in communities of associations distributed on soils of a full range of a salinity degree (both weak- and strongly-salted). Compared to associations on strongly salted soils, they slightly strengthen their positions in these ones with weakly salted soils - both species are registered there more often, and Echinochloa crus-galli is even more plentifully.

Анализ современного использования природно-территориальных комплексов ландшафта дельты реки Волга в сельскохозяйственных целях

Анализ современного использования природно-территориальных комплексов ландшафта дельты реки Волга в сельскохозяйственных целях

Методы и алгоритмы оценки ландшафтного разнообразия в морфологическом аспекте на примере центральной части дельты реки Волги

The article presents a methodology for assessing landscape diversity, which allows to obtain a comprehensive numerical characteristic of the geographical environment, integrating the properties of its stability, which determines the characteristics of economic use. The identification and analysis of the landscape diversity of natural-territorial complexes is an urgent task that is in the center of attention of ecological and geographical research. On the basis of digital landscape maps, the results of experimental studies of system relationships of functioning of natural-social-production systems and structural-genetic landscape studies for the first time landscape diversity of the central part of the landscape of the Volga River delta was made. In this paper, we analyzed a number of basic landscape metrics used in assessing landscape diversity for the territory of the central part of the landscape of the Volga River Delta. Among them: the average area of landscape sections, the index of landscape fragmentation, the index of landscape complexity, the coefficient of landscape fragmentation, the index of landscape mosaic, the index of relative wealth, the Menninik index. To create schemes of landscape diversity, the method of nets in the form of hexagons, which is hardly used in domestic landscape mapping, was tested. The study and assessment of the landscape diversity of the indigenous tracts of the central part of the Volga River Delta proves that such a study makes it possible to choose the right decisions when organizing the territory. It takes on leading significance in the justification of economic activity and is a necessary component of design. Studies have shown that the largest number of undisturbed natural territorial complexes is found in areas with a high degree of landscape diversity. Many of them territorially coincide or are close to sites with the status of specially protected natural areas.

Change in species composition of vegetation on various-aged set-aside lands of the Volga Delta

The object of the present research is set-aside lands of various ages. The study was aimed to identify the main biological groups of weed growing on set-aside lands of the Volga Delta, which were removed from production in different years. Within the study, species composition of set-aside lands’ vegetation was defined, which amounted to 28 species and 16 families. The plant community of set-aside lands includes such large families as Asteraceae (5 species), Poaceae (4 species), Brassicaceae (3 species). It was observed that quantitative species composition of set-aside lands’ flora has been changing depending on its age: the older a set-aside land is, the less species grow there. In spring and summer seasons, ephemeral, annual and biennial weeds prevailed, while in autumn perennial plants did: the latter were estimated of 75-80%, their wet weight amounted up to 70-92% of total weight due to the plentiful growth and development of a perennial rhizome plant named Phragmites australis (Cav.) Trin. ex Steudel. The research has lasted for 10 years and allowed observing a 14-32% increase in a number of plants belonging to a xerophyte group on longstanding set-aside lands with low level of soil moisture. Agro-ecosystems of various-aged set-aside lands hosted the development of flora having different vegetative weight that is capable of accumulating solar energy. Significant amount of accumulated energy reduced the entropy of the environment and improved its ecological state. On an old-aged set-aside land, corps of perennial plants vegetating for a long time have been maximally accumulating energy and gained 25712.42 MJ/ha.

Effect of growth regulators on productivity and quality of tomato crop under Volga delta conditions

Relevance. Tomato considered a significant vegetable crop that plays a prominent role in the field of human health. At present, there are large numbers of tomato cultivars with a wide range of morphological and sensorial characteristics which determine their use. Farmers often use some chemical substances which have similar structure and activity with endogenous plant hormone called (exogenous) as a low-cost alternative to regulate plant growth and increase yield. Thus, the use of Plant Growth Regulators (PGRs) has become an important component of the agro-technical procedures for most cultivated species.Methods. This study aims to evaluate the effect of four growth regulators (Krezacin, Chitosan, Zircon and Energene) on growth, productivity and quality of two Russian tomato varieties (Moriana and Superjol) under delta Volga conditions. Each type applied three times on both cultivars (Soaking tomato seeds before sowing, spraying on plants at vegetative phase, spraying on plants at flowering phase with three replications.Results. The results showed that; combination between Energene and cultivar Moriana enhanced the most of studied characters (Germination – 83.1%, fresh weight of Arial parts – 241.9 g, dry weight – 74.4 g, Number of № flowers/plant – 51.0, № fruits /plant – 35.6, fruit set – 69.8%, plant yield – 2.44 kg, TSS – 5.1°Brix, Content of Ascorbic Acid – 25.6 mg/100 g); Interaction between “Energene x Superjol” gave the maximum value for Plant height (85.6 cm), Fruit weight (72.6 g); while “Krezacin x Moriana” registered the highest fruit dry matter (6.77%) and Acidity (0.53%); Applying Zircon on Cultivar Moriana increased number of leaves/plant (56.8) and nitrate contents (27.6 mg/kg); the maximum LAI (150.1 cm2 ) obtained from interaction between Chitosan and cultivar Superjol whereas, “Chitosan x Moriana” treatment gave the highest level of Carotenoids (4.12%).

Morphological properties of underwater soils of river deltas

The results of the study of the morphological properties of underwater soils in the deltas of the Volga, Don and Kuban rivers are shown. This paper is based on field descriptions of profiles of underwater soils found in deltas. Genetic horizons have been identified, their basic properties (pH, Eh, electrical conductivity, grain size composition, organic carbon content) have been studied and the main types of soils, which are formed under different types of sedimentation and under different types of aquatic vegetation, have been described. Names of horizons and types of soils are given due to the classification of underwater soils (aquazems) of the Volga delta, that had been proposed previously. The diversity of underwater soils of three deltas has been studied, and the properties of the same soil types formed in different deltas have been compared. The features of underwater soils formation are described; the difference between the factors of underwater and terrestrial soil formation is discussed. It is shown that the number of occurring soil types depends on the diversity of the emerging types of aquatic landscapes and the contrast of the conditions of migration and accumulation of matter. Necessary conditions for the forming of underwater soils and the possibility of relating bottom sediments to soil formations are discussed. Our results are indicative of the need of studying bottom sediments with soil-like profile from the standpoint of soil science and the inclusion of aquazems into the modern Russian soil classification.

Анализ застройки на основе данных дистанционного зондирования Земли оптического и радиоволнового диапазонов

Monitoring and mapping development areas is a key task in solving a number of applied studies, for example in urban planning, geoecology, etc. Development is a key indicator in calculating the degree of landscape naturalness. In the first part of this article the author a briefly overviews the problem of identifying the degree of anthropogenic pressure on natural territorial complexes. The experience of using optical band data on the example of Landsat 8 (OLI) and Sentinel-2B and the process of processing radar data Sentinel-1A specifically for analyzing areas of development are described the second part of this paper. The research area is the central part of the Volga delta. Thus, as a result of a combining Landsat 8 (OLI), Sentinel-2B and Sentinel-1A satellites data, the density of the Volga Delta territory central part was obtained (190 km2). These materials provide a basis for further research in the field of revealing the degree of anthropogenic impact on natural landscape, serve as an informative source for scientific and applied research in various directions. The obtained data can be transferred to the Department of the Federal Service for State Registration, Cadastre and Cartography of the Astrakhan region for updating the archive information.

Results of Our Long-Term Observations on Stationary Transects in the Volga-Akhtuba Floodplain

By the beginning of the 1970s, only two large regions with natural vegetation, namely the Volga–Akhtuba floodplain and the Volga delta, had remained in the Volga River valley. The largest part of the remaining valley had been converted into a cascade of reservoirs. The conservation of meadow, marsh, and forest plant communities in the lower reaches of the Volga River located in the semi-desert and desert zones is due to regular water releases of the Volgograd hydroelectric power station downstream. These artificial water discharges into the Lower Volga valley in the spring–summer period have taken the place of natural floods. However, in the conditions of regulated water flow, the rise in the water level decreased during floods and the duration of flooding of the floodplain ecotopes shortened. The river channel deepened along a 100-km river section in the near-dam part of the Volgograd hydroelectric power station in the northern part of the floodplain. These dams hinder water flow to the Akhtuba–Volga floodplain during spring and summer floods. They surround agricultural lands with artificial irrigation systems and settlements in the floodplain. The recreational use of the Lower Volga valley has increased in the past few decades. Before the construction of the largest Volga hydroelectric complexes (the Kama, Gorky, Kuibyshev, Volgograd, and Saratov ones) in 1954–1955, five geobotanical transects were laid out in the course of the Caspian expedition of Moscow State University. Subsequently, four of the transects were surveyed in 1982 and 2008 –2013. It was established that xerophytization and ruderalization of vegetation occurred on all transects. These phenomena were not similar in different sections of the floodplain. They were most pronounced near the Volgograd Hydroelectric Power Station and in the places of narrowing of the valley. The reduction in the height and duration of floods after the regulation of the water flow, high local grazing, and recreation pressure is the main reason for xerophytization and ruderalization of vegetation. Among the invasive species, Fraxinus pennsylvanica, Conyza canadensis, Bidens frondosa, and Xanthium strumarium s.l. play the most important role in changes in the vegetative cover of the Volga–Akhtuba floodplain. Thus, not all phenomena related to the dynamics of the vegetation and flora in the Volga–Akhtuba floodplain were caused by restructuring of the Volga hydrological regime after regulation of its water flow. The invasion of alien plants, increased recreation load, and changes in the economic use of the vegetation cover in the territory have played a particular role in this process.

Rheoreaction of Some Juvenile Cyprinids During Autumn Contranatant Migration

The contranatant migration of juvenile cyprinids was studied in the Volga River delta in September–November 2016. A motivational component of rheoreaction (the ratio of rheoreaction types) of migrating and nonmigrating juveniles was evaluated in the course of experiments. It is shown that the motivational component of rheoreaction is a behavioral mechanism of contranatant migration.

The modern state of the ecosystem in the Volga River delta ecotone and dynamics of the changes in water availability conditions

We prove that an abrupt amount of water-soluble salts in soils occurs due to rapid increase in heat provision under decrease in precipitation amount for the period with the temperatures above 10°C (under the integrated index of territories aridity, the G.T. Selyaninov coefficient is up to 0.3 or less). Based on the results of investigations from 137 model sites at the Volga River delta in the years with water availability contrast conditions (2014 and 2015 are years with little water and 2016 and 2017 are water-abundant years), we indicate a decrease in the volume of river runoff according to the landscape-ecological complex of soil-plant cover. We also show the toxicity level due to the increase in toxic Cl-, Na+ and Mg2+ under simultaneous decrease in the content of SO42- and Ca2+ ions. Moreover, there is a change in soil salinization type from chloride-sulphatic to sulphatic-chloride, which directly affects plant cover: total biomass and foliage cover decrease on all deltoid landscapes of high levels, the participation of sedge and herbs decreases, and role of forbs increases. These processes are blocked due to the rise of the subsequent conditions of abrupt water availability and move back. The greatest and the most rapid changes are observed within particularly extended alluvial natural boundaries of low level in the vegetation classes Phragmitetea R. Tx. Et Preising 1942 and Bolboschoenetea maritime Vicherek et R. Tx. 1969 ex R. Tx. et Hulb. 1971 at the level of associations and types.

Results of investigation of ticks in Volga river delta (Astrakhan region, 2017) for Crimean-Congo hemorrhagic fever virus (Nairoviridae, Orthonairovirus, CCHFV) and other tick-borne arboviruses.

There are natural foci of Crimean-Congo hemorrhagic fever (CCHF) that vectored by Hyalomma marginatum ticks in Volga river delta (Astrakhan region, South of Russia). The circulation of Dhori virus (DHOV) (Thogotovirus: Orthomyxoviridae) has been also shown here. We hypothesized that other tick-borne arboviruses are also likely to circulate in the region. In particular, Bhanja virus (Phlebovirus: Phenuiviridae), Wad Medani virus (Orbivirus: Reoviridae), and Tamdy virus (Orthonairovirus: Nairoviridae), which were found to circulate in neighboring regions and are vectored by Haemaphysalis spp., Dermacenter spp., and Hyalomma spp. ticks. The aim of the study was to examine ixodid ticks in Volga river delta for the presence of CCHFV, DHOV, Bhanja virus, Wad Medani virus, and Tamdy virus. Ticks were collected in Volga river delta in 2017. We used molecular genetic methods for the detection and analysis of nucleic acids (PCR, sequencing, phylogenetic analysis). We detect CCHFV and DHOV RNA in H. marginatum ticks. The rate of infected H. marginatum ticks was 1.98% for CCHFV and 0.4% for DHOV. The results of genetic analysis showed that found DHOV strains are almost identical (99-100% in the M gene) and forms a separate genetic lineage alongside of Batken virus from Central Asia. At the same time, Bhanja virus, Wad Medani virus, and Tamdy virus were not found in ticks, collected in this region. DHOV is circulating in the natural foci of CCHF in the Volga river delta. The ratio of infection of H. marginatum with CCHFV and DHOV was determined for the first time.

Thermal tolerance of Cyclops kolensis lilljeborg, 1901 (Copepoda: Cyclopoida) and its relationships with pessimal to optimal performance.

Cyclops kolensis Lilljeborg, 1901 belongs to the Arctic complex of Palaeoarctic species, yet in the past 20 years, its occurrence has extended to the summer months in waterbodies with high water temperatures. This species is considered one of the most active migrants from the northern waterbodies in the Volga reservoir cascade to the Volga delta. Here, we explored the ranges of the preferred and avoidance temperatures of C. kolensis from two geographically isolated populations. Thermal tolerance was measured in a thermogradient installation and compared to the temperatures at which members of these populations occurred in their source waterbodies. Temperature preference was determined using the "chronic" method. Individuals of C. kolensis possessed a bimodal final temperature preferendum of 2-6 °C and 13-21 °C, which corresponds to the optimal thermal conditions of the species in a pond. These ranges were the same for individuals of both populations irrespective of the geographical location and water temperature of their source waterbodies. The temperature range of normal performance was 2-4 to 21-25 °C, and the pessimal temperature ranges were from 1 - 2 to 3-4 °C and from 22-25 °C to 26-30°С. These temperature ranges coincide with field observations over a recent 20-year period of temperature conditions under which the species develops in nature. Our results allow us to characterize C. kolensis as an ecologically plastic species, which, despite its strong association with the cold-water Complex species, is adapting to a wider temperature range as global warming occurs.

ОСОБЕННОСТИ ФОРМИРОВАНИЯ ЖАБР У МОЛОДИ ВОБЛЫ НА НЕРЕСТИЛИЩАХ ДЕЛЬТЫ ВОЛГИ

The article focuses on the influence of anthropogenic load initiating multidirectional metamorphosis of biological processes in the aquatic organisms in the Volga delta. The gill apparatus responds primarily to the environmental changes. There has been carried out a histological study of the gill apparatus of carp species, actually, late larvae and early roach fry, which helps to identify and describe the ecological situation on the spawning grounds in the Volga delta. Various morphological changes in the gills indicating respiratory disturbances were revealed. The late roach larvae and fry have been found to obtain the overgrown respiratory epithelium on the lamella tops, proliferation of multilayered non-keratinizing epithelium, vasodilation, deformation and curvature of the cartilage plate and filaments, lack of lamellae, joining of the side surfaces and filament hemorrhage. It has been stated that in comparison with the larval stages of development, in the fry period the occurrence of the respiratory epithelium accretion increases. The changes found in the gill apparatus of the examined roach larvae and fry indicate the unsatisfied physiological state of the fish in some water bodies of the Volga delta. This is explained by the fact that the gills suffer from the direct impact of the negative factors of the aquatic environment including different pollutants in the flooded water bodies.

ВЛИЯНИЕ ОБЪЕМА СТОКА И РЕЖИМА ПОЛОВОДЬЯ НА КАЧЕСТВЕННЫЕ ХАРАКТЕРИСТИКИ МОЛОДИ ЛЕЩА (ABRAMIS BRAMAORIENTALIS L.) В ВОСТОЧНЫХ И ЗАПАДНЫХ ЧАСТЯХ ДЕЛЬТЫ РЕКИ ВОЛГИ

The paper presents the assessment results of the influence of hydrological conditions on the qualitative characteristics of bream juveniles in the Volga delta. The influence of factors (volume, hydrological characteristics of spring flood, temperature conditions) on the spawning periods of producers, duration of feeding of juveniles at spawning grounds, including viable ones, at the end of the hollow period has been traced. There have been presented the comparative data on the age, distribution and qualitative composition of larvae and juveniles obtained in the course of the research works at spawning grounds in different regions of the lower reaches of the Volga River in 2011-2017. The most favorable conditions for feeding on young bream have been found to form in the high-water years (2013 and 2016) and in the mid-water year (2017). Years 2011 and 2015 became critical for natural reproduction; years 2012 and 2014 were unfavorable. The highest size-weight characteristics of bream juveniles were observed by the end of the hollow period in the east of the delta in the arid and middle water years, and in high-water years they were found in the Volga-Akhtuba floodplain. The qualitative characteristics of bream in the east in low-water years were maximum in the upper zone, minimal - in the middle zone, in the western spawning grounds there was observed a reverse situation. In high-water years the highest values of bream juvenile size-weight parameters were observed in the middle zone in the east of the delta. In the mid-water year (2017) in the eastern part of the delta the maximum feeding results were observed in the lower zone, and in the spawning grounds of the western delta - in the middle zone. By the end of the feeding period in high-water years practically all bream juveniles (98.4%) reached the viable stage of development, and in arid years only 28.4% of bream juveniles reached the stage.

АНАЛИЗ ПРОДУКТИВНОСТИ ГУБКИ ИЗ СЕМЕЙСТВА SPONGILLIDAE, ПРОИЗРАСТАЮЩЕЙ В ВОДОЕМАХ РЕКИ ВОЛГИ, В ПЕРИОД РЕГРЕССИИ КАСПИЙСКОГО МОРЯ

The article describes the habitat, systematics and species of freshwater sponge ( Badiaga spongia fluviatilis ) inhabiting water bodies of Russia. There have been characterized the hydrological features of water bodies - sponges’ habitats, and their ecological function has been characterized. In freshwater bodies of the central Russia there occur two most common and numerous types of sponges - lake badiaga ( Spongilla lacustris ) and river badiaga ( Ephydatia fluviatilis ) presenting a valuable raw material for the pharmaceutical and cosmetic industry. The attention is focused on the fact that sponge colonies can reach the commercial volumes only in the floodplain waters and the delta of the Volga River. Retrospective data on volumes of sponge fishery in the Astrakhan region suggest the reason for decreasing sponge productivity and volume of the sponge industry: a lack of reclamation works in small rivers in the Volga delta. There has been given a comparative analysis of the data on microscopic studies of sponge structure caught on experimental zones in the water bodies of the Astrakhan region and the information found in the scientific literature. Characteristics of soils where significant sponge plantations were found are analyzed. It has been stated that in the watercourses of the Astrakhan region there prevail species of lake sponge ( Spongilla lacustris ), whose biomass should increase tenfold taking into account the cyclicity of the regression processes of the Caspian Sea, carrying out complex ameliorative works on the waterways of the Volga and development of agriculture and livestock breeding. It has been recommended to prepare a scientific and production base for the rational and effective development of the potential of this natural resource for pharmaceutical and cosmetic purposes.

The approach to the regulation of mercury according to the content of its termoforms in soils and bed loads

The article contains the results of the ecological and hygienic diagnostics of conditions of lands of areas of different sizes and varying degrees of urbanization, located in different agro-climatic conditions of European Russia (the southern Astrakhan region, he city of Moscow). Assessments of the state of territories use a new approach to rationing of Hg according to quantitative ratios of the content of its thermoforms in soils, grounds and alluvium (in litho substrate). The method of diagnostics is based on known properties of Hg forms: their geochemical activity (migration mobility) and toxicity decline along with the increment of the Hg temperature threshold of the release in the process of continuous warming up of the litho substrate sample (up to 1100°C). Thermoforms are not tied to specific minerals or chemicals and are conditionally designated as FR (Free: <180°C), CL (Chloride: 180-250°C), FS and CS (physically and chemically sorbed: 250-400°C), SU (Sulfide: 400-500°C) IS (isomorphic: >500°C) Hg forms. Among forms, also conditionally according to complexes of low, medium and high temperature variations(FR + CL, FS + CS and SU + IZ, respectively, there are selected groups of «mobile», «sustainable» and «inert» forms. For technogenic Hg there is characterized the predominance in the sample of «mobile» and to lesser extent degree - «stable» thermoforms. The more intensive this predominance is, the higher is environmental hazard. The natural accumulation is diagnosed by the presence and prevalence of the sum of moderate - and high-temperature inert forms of Hg. According to the ratios of Hg content, its forms and groups, as well as the density of correlationships between them, 6 indices of the conditions of soils and alluvium were developed by ourselves.Main coefficients out of indices on informativeness of results of diagnostics are the following factors: Endogenous input, Geochemical activity and Hg mobility. With regard to the combination of variability in indices, the total amount of Hg, the genesis and intensity of its accumulation (natural or anthropogenic), there were also developed ranking scales of the ecological and hygienic condition of the land areas and surface water bodies. As a result, on the base of such approach to the regulation of Hg the information value of assessments of mercury contamination of land significantly increased. At the objects of assessments there were identified following areas: foci of the manifestation of Hg hypolimnetic emanations on the landscape surface - dispersion halos in the areas of the Earth crust fracture (the dome of the Astrakhan gas condensate field); environmentally dangerous (sometimes even at a low total content of Hg) parts of cities, towns, their districts, as well as beds of watercourses and water reservoirs bottom (the Volga river valley and delta, the Lefortovo quarter in Moscow). There was also diagnosed the threshold of the background distribution of gross Hg content detected = 0.2-0.3 mg/kg. Its magnitude is consistent with domestic and abroad safe levels of Hg accumulation in soils = 0.3-0.4 mg/kg. The approach provides the differentiation of the environmental hazard lands. Technology of the approach can be used in the development of normative Document for the diagnosis of environmental and sanitary condition of territories in the system of Classifications of hazard of waste, in decontamination of territories, water areas and land zoning according to the criteria of natural or anthropogenic Hg accumulation.

Особенности химического состава речных раков

The cultivation of crayfish in the structure of aquaculture in the Middle Volga region can be an important component. Currently, natural crayfish populations in the Republic of Tatarstan include 2 species – narrow-toed crayfish (Pontastacus leptodactylus Esch.) and wide-toed crayfish (A. astacus L.). The development of aquabiological technologies allows the use of natural crayfish populations for the tasks of creating industrial breeding farms. In connection with the global trend of the growing popularity of crayfish in food use, the importance of research on the chemical composition of crayfish as objects of consumption grows. The chemical analysis of narrow-fingered crayfish revealed 13 elements, of which calcium is found in maximum amount in the dry residue. The calcium content in the narrow crayfish was 154.057 g/kg dry weight (fig. 1), the chitinous shell of crayfish contains relatively more calcium – up to 376.282 g/kg of dry weight. The following sequences of the content of chemical elements in crayfish from the Kuibyshev reservoir are noted:  in the muscle tissue of edible parts Ca ˃K ˃S ˃P ˃Cu ˃Fe ˃Zn ˃Mn ~ Br ˃Sr;  in the shell Ca ˃Si ˃P ˃S ˃K ˃Sr ˃Ti ˃Fe ˃Mn ˃Cu ˃Br ˃Zn ˃As. In crayfish from the Kuibyshev reservoir we studied, the raw muscle mass of the edible parts of the crayfish contained 88.80% of water, 10.28% of organic substances and 0.92% of mineral substances, and in the chitin-containing raw shells of crayfish, respectively, contained 59.2% of water, 36.42% organic matter and 4.38% mineral matter. The particular interest is the study of crayfish shells, since they consist mainly of chitin. It is a bearing polysaccharide for invertebrate, reaching 85% of the weight of the integuments. In the cuticle of arthropods, chitin forms composite complexes with proteins, pigments, calcium salts. In the composition of the shells of crayfish, 376.282 mg/kg dry mass of calcium is noted. In smaller quantities phosphorus, potassium, iron and zinc are noted. Titanium was found in crayfish shells in the amount of 1845 mg/kg dry weight and was not found in their muscle tissue and other aquatic organisms in the region. In the studied crayfish, the content of heavy metals in the wet mass was: Zn – 0.42 mg/kg; Cu 6.5 mg/kg; Fe – 1.39 mg/kg; Sr – 0.23 mg/kg. Residual amounts of zinc and copper in the muscular tissue of the edible parts of crayfish of the Kuibyshev reservoir are within the normal range. The content of hazardous elements (lead, arsenic, cadmium and mercury) in the crayfish from the Kuibyshev reservoir is within the sanitary and epidemiological norms, and in the Volga delta crayfish the lead content is exceeded.

Assessment of the ecological state of the surface waters of the Nikitinsky fish passage channel during dredging work

Fish passage channels along the main delta watercourses serve for upstream spawning of fish and stingrays of young and adult fish back to sea, thereby preserving and multiplying the biodiversity of the ecosystems of the Caspian basin. The flickering sections of the canal-fish passage require periodic dredging. When analyzing the ecological and geochemical situation of the territory, one of the most informative objects of research is surface water. Accumulating pollutants coming from watersheds over a long period of time, soils are an indicator of the ecological condition of the territory, a kind of integral indicator of the level of pollution. As part of the study, an assessment was made of the ecotoxicological state of the surface waters of the fish passage channel during dredging in the Volga delta, the environmental toxicological status of the coastal zone of the canal was analyzed according to accepted standards, possible adverse environmental changes were predicted, and proposals were developed for a program of production ecological monitoring the nature of changes in surface water quality as a major component of the ecosystem.

Fossil diatoms from the Volga Delta Holocene sediments (Damchik region) as indicators of the paleoecological conditions of sedimentation

The results of fossil diatoms investigation from the deltaic sediments are presented. Samples were obtained from the core DM-1 and two Holocene outcrops from the Damchik region of the Astrakhan Nature Reserve. In the core samples eight periods of sedimentation based on diatom analysis were identified: the sediments formed in shallow freshwater basins and deltaic channels. The samples from the outcrops were investigated in much greater detail.

ЭКОЛОГИЧЕСКИЕ ОСОБЕННОСТИ УСТОЙЧИВОСТИ К АНТИБИОТИКАМ УСЛОВНО-ПАТОГЕННОЙ МИКРОФЛОРЫ, ПЕРСИСТИРУЮЩЕЙ В ГИДРОЭКОСИСТЕМАХ

The article provides an overview of investigating antibiotic resistance of conditionally pathogenic microflora circulating in different hydroecosystems. It has been stated that the process of spreading antibiotic resistance in bacteria around the world is progressing in a large scale. It has been found that the peculiarities of its manifestation are largely determined by natural, climatic and anthropogenic factors, as well as by the level of urbanization. Mechanisms of microorganism interaction with separate antibiotics are studied. The data obtained show that antibiotics widely used in medicine, veterinary science and aquaculture have caused antibiotic resistance in microflora isolated from hydroecosystems and hydrobionts (fish). The study results of the Russian and foreign scientists on antibiotic resistance of bacteria isolated from water and fish have been brought. Thus, microorganisms isolated from urban watercourses of Astrakhan, the Volga river Delta and pike perch body organs showed multiple antibiotic resistance depending on the season and the studied area. In all cases there have been recorded the minimum resistance of microflora to tobramycin and chloramphenicol and the maximum - to benzylpenicillin and ampicillin. The obtained data can serve as indicators of sanitary and epidemiological and environmental problems of hydroecosystems.