Watering of the river delta Volga and Western sub-steppe ilmens based on simulation hydrodynamic modeling

To ensure the flooding of the Volga river delta and the Western sub-basin Ilmen and meet the requirements of the fisheries and agriculture, the following tasks were set and completed: to describe the current state and the main environmental, fisheries, agricultural and transport problems of the functioning of the Volga Delta and the Western sub-basin Ilmen; to develop a computer simulation model in the software package MIKE 11 plot of the Volga river from Verkhneye Lebyazhye village before flowing into the Caspian sea, with the specification of cross-sections along the river bed and the floodplain of the Volga river and its branches, spawning grounds, and western sub-steppe ilmen; to perform computer hydrodynamic modeling of the studied section of the Volga river; to develop possible scenarios to solve the problems of flooding of the Volga river delta and the western sub-steppe ilmen, and to meet the requirements of fisheries and agriculture. As the result, the requirements of the main water users for the operating modes of the Volga hydroelectric power station were presented and a hydrodynamic model was described, which allows determining the measures for watering the territory and using simulation modeling to evaluate their effectiveness.

Halotolerance of pseudomonads isolated from aquatic environment and fish (Sander lucioperca) in the Volga River delta

Introduction. The material shows halophiles bacteria R. Psendomonas the water’s microbiota and the pikeperch in spring and autumn. The attachment of Pseudomonas isolated from these habitats, certain Delta areas has not been identified. Materials and methods. 190 “water” strains and 720 ones isolated from fish were experimentally tested. In meat-peptone broth (MPB) with 3.0, 7.0, and 10.0% NaCl content, daily cultures of analyzed bacteria were sown, incubation of which was carried out at 37 0 C, and the results were taken into account after 24 and 48 hours. Results. There were no significant differences in halophilicity in the analyzed strains, except for the autumn season, especially in 10.0% salt solution. Among the isolated pseudomonads, the maximum halotolerance in both biotopes was observed in P. fluorescens and P. alcaligenes in P. putida. Halophiles strains of Pseudomonas that infect the water and fish had seasonal cycles. A slight decrease in the halophilicity of pseudomonades persistent in water and fish only at concentrations of 3.0 and 10.0 mg/l from spring to summer (1.1-1.2 times), and their significant rise in autumn (1.5 and 1.4 times) in the salt concentration of 3.0 mg/l. In the tested strains in spring and autumn, increased salt tolerance values were noted, which was determined by the hydrological and hydrochemical features of Delta waters and the “transfer” of bacteria in the body of walleye during its migration from the sea to the river. Conclusion. Analysis of long-term material showed high halophiles studied strains of pseudomonad, indicating that their sanitary and epidemiologic danger, and the ability to remain viable in salted fish products

Present distribution and variability of water flow, suspended sediment load, and geochemical runoff in the Volga River delta

<p>Environmental changes in the Volga River delta attract attention of researchers due to increasing anthropogenic pressure on the river catchment, global climate changes, and natural fluctuation cycles of the Caspian Sea level. These changes significantly affect the hydrological regime and erosion-accumulative processes in the Volga delta.</p><p>In 2018-2020, the authors conducted series of field hydrological and geochemical studies within the Volga River delta, which covered all major systems of the deltaic water streams. We have determined water discharge, suspended sediment concentration, content of dissolved and suspended chemical elements (ICP-MS/ICP-AES). The results obtained in the study provide a comprehensive view of the current spatial and temporal distribution of the water flow, suspended sediment yield, and geochemical flows along the main branches, numerous channels and rivers during the both high and low water periods, and also allow us to compare them with long-term trends established by previous studies.</p><p>We have found that the present distribution of water flow and suspended sediment load within the Volga delta differs from the second half of the XX century. It determines the ongoing restructuring of the water balance, and transformation of the rate of erosion and accumulative processes within the main systems of the deltaic branches. The study allowed delineating the Volga Delta by zones of erosion, transition, and accumulation of suspended matter in different phases of the water regime in relation to the modern basis of erosion, which is the current level of the Caspian Sea.</p><p>The distribution of geochemical runoff within the Volga Delta is determined by water and sediment runoff, as well as concentrations of dissolved and suspended forms of chemical elements. The largest geochemical runoff passes through the Bakhtemir and Buzan systems. During the low-water period, the volumes of geochemical runoff of these branches are similar. During the flood period, despite the increasing share of Buzan water runoff, the prevailing fluxes of matter pass through the Bakhtemir system due to higher concentrations of elements and larger solid discharge.</p><p>The ratio of dissolved and suspended elements in flows is determined mainly by the properties of chemical elements. According to the percentage ratio of dissolved and suspended forms, we divided elements into 3 groups: 1) migrating mainly in dissolved forms (Na, Ca, Sr, Mg, Mo, U, K, Li, Ba, As, Sb), 2) migrating mainly in suspended forms (Pb, Y, Zr, Ti, Mn, Fe, Al, REE), 3) elements with changeable behavior depending on geochemical and hydrological conditions (Ni, Cd, Zn, Co, Cu, et al.).</p><p>The research was supported by RFBR project No. 18-05-80094 and №17-05-41174-RGS.</p>

MAIN PERIODS OF FISHING PROHIBITING IN THE VOLGA RIVER DELTA AND THEIR BIOLOGICAL SENSE

The article presents an analysis of the Fisheries Rules for the Volga-Caspian fishery subarea (Astrakhan region) in terms of establishing time limits for the catch of living resources. The dynamics of the limits duration, the timing of its beginning and end in different versions of the Fisheries Rules for 150 years is shown. It was revealed, that in the modern Fisheries Rules the timing of fishing for living resources is set in accordance with the features of their life cycle in the lower Volga, ensuring the preservation and growth of the basin’s stock. Biological inexpediency of further prohibition periods shortening is noted.

Methods and algorithms for assessing landscape diversity in morphological terms on the example of the central part of the Volga River Delta

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.

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

Introduction. 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.Goals and objectives. 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.Material and methods. 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).Results. 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.Conclusions. 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.

ECOLOGICAL CHARACTERISTICS OF ANTIBIOTIC RESISTANCE OF CONDITIONALLY PATHOGENIC MICROORGANISMS PERSISTENT IN HYDROECOSYSTEMS

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.