Adaptive and pathological responses of cyprinidae liver towards habitat in the Volga delta

Human impact on ecosystems makes it imperative to monitor populations of different fish species from various perspectives. The consequence of environmental impact on living organisms is the reactions of organs and organ systems, which find their reflection in pathological changes in the fish body particularly. Reactions in the fish body are the result of the combined influence of environmental factors and natural physiological processes associated with feeding, migrations, generative cycles, etc. The changes in the structure of organs detected in fish make it possible to assess the influence of the environment on fish. The research was carried out in the Volga delta, the Bereket (upper delta) and the Kostyl (lower delta) rivers. Reservoirs for research were chosen in such a way that they were subject to anthropogenic influence to varying degrees. Unfavorable living environment represented by pollutants increase the functional load on the liver. The research has shown an increase in the liver index in fish from reservoirs with a higher level of anthropogenic load. Metabolic functioning of liver cells is considered as an important protective mechanism against toxicants, while the associated transformations are somehow connected with detoxification. Histological preparations were made according to standard methods.

REACTIONS OF KIDNEYS OF SILVER BREAM (BLICCA BJOERKNA) FROM VOLGA DELTA TO HABITAT

The article focuses on the intensive anthropogenic impact on the aquatic ecosystems, which makes it necessary to monitor the populations of different fish species. The method of mor-phophysiological indicators was used to study the kidneys of silver bream in different water bodies of the Volga Delta. The morphometric characteristics of the kidneys of silver bream are presented. It is shown that the reactions of organs and body systems are caused by the environmental impact on the living organisms, which results, in particular, in the pathological changes in the fish body. Reactions in the body of fish are the result of a combined effect of environmental factors and natural physiological processes related to feeding, migrations, generative cycles, etc. The detected changes in the organ structure make it possible to assess the impact of the environment on fish. The seasonal and sexual variability of the indices of the mesonephros of silver bream from the Volga Delta is shown. Analysis of the kidneys of fish from two water bodies showed the variability of kidney mass due to the anthropogenic load on the water body, in particular, an increase in the kidney index in silver bream Blicca bjoerkna was registered in the ecosystem with an increased toxic load. It has been stated that the increase in the relative mass of mesonephros was caused by the changes in the organ. Changes were detected both in the intratubular tissue, and in the convoluted tubules and renal capsules. The study helped to find the differences in the relative weight and structure of the kidneys of silver bream, which lives in the water bodies with different anthropogenic load. A real increase of the kidney index was found in fish from the water body with a higher level of anthropogenic impact.

SANITARY AND ECOLOGICAL IMPORTANCE OF BACTERIA OF THE GENUS ACINETOBACTER ISOLATED FROM WATER AND FISH IN VOLGA DELTA

The article highlights the study of the sanitary and ecological features of acinetobac-teria,which were isolated from the water and fish in the Volga Delta in the period from 1987 up to 2010. Today, these bacteria are among the most dangerous pathogens for people, especially in hospitals. They can exist in hydroecosystems and interact with aquatic biota. There were analyzed 96 beluga species; 295 sturgeon species; 217 stellate sturgeon species; 50 sterlet species; 173 carp species; 447 zander species; 638 water samples in the fishing areas. There were examined the fish, parenchymal organs, intestines, gills, blood, gonads (in sturgeon), and muscle tissues. Pathogenicity factors were taken into account: growth at 37°C, fermentation of hemolysin, protease, lecithinase, catalase; viability in 3.0; 7.0; 10.0% broth with NaCl. It is shown that the occurrence of Acinetobacter in water ranged from 3.0 to 16.7%; in fish-from 4.6 to 10.5% of samples of the entire isolated microflora. Inferior to the dominant enterobacteria and aeromonads, acinetobacteria isolated from water and fish had all the analyzed pathogenicity factors, especially catalase activity. In combination with halophilicity, these bacteria can be preserved in fish when stored frozen and as salted fish products.

COMPARATIVE BIOELECTRONIC DIAGNOSTICS OF THE ECOLOGICAL STATE OF POLLUTED WATER AREAS (ON THE EXAMPLE OF SOME CHANNELS OF THE VOLGA DELTA)

The objects of bioindication of the ecological state were 3 channels of the Volga Delta, located both directly in Astrakhan and in the Astrakhan region. The aim of the work was to conduct a comparative bioelectronic diagnosis of the ecological state of the selected channels with different local anthropogenic loads, both by type and size, based on assessments of the functional state (health) of the bivalve mollusks Anodonta anatina living in them, estimated on the basis of an analysis of their cardiorhythm, measured using an original fiber-optic bioelectronic system. It was found that shellfish selected from different water areas, after 1hour functional load, restore the original heart rate for different times, but in the range from 117 to 166 minutes, which is typical for shellfish living in significantly polluted reservoirs of the same ecological status - "Bad". This characteristic of the water areas completely coincides with the characteristic of the ecological state of the channels of the Volga River Delta specified in the State Report "On the state and on Environmental Protection of the Russian Federation in 2017". The authors proposed and justified the possibility of using the water area of the Gandurino River as a conditional reference for the Volga Delta region. In this case, according to the value of the environmental quality coefficient EQR, the channels of the Urban Branch and the Small Channel can be attributed to the regional environmental status - "Good".

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>

Functional state of the organism of the hybrid Russian sturgeon × Siberian sturgeon (Acipenser gueldenstaedtii × Acipenser baerii) after winter in cages in Volga Delta

Two-year-olds (15 individuals) and five-year-olds (15 individuals) of the Russian sturgeon × Siberian sturgeon (Acipenser gueldenstaedtii × Acipenser baerii) hybrid, kept in net cages in the Volga delta, were studied after wintering in order to establish the functional state of the organism according to the complex of indicators of the erythron system and metabolism substances. The results of the performed study found that the erythron system in five-year-olds is characterized by a higher content of erythrocytes and blood hemoglobin (0.58 ± 0.01×10 12 l –1 and 64.98 ± 1.29 g/l, respectively), compared with two-year-olds (0.49 ± 0.02×10 12 l –1 and 64.98 ± 1.29 g/l, respectively).The serum iron content in both groups was the same. A higher content of total protein and albumin in the blood, as well as a greater activity of ALT were found in five-year-olds, compared with two-year-olds. Thus, the content of total protein and albumin in blood serum in five-year-olds was at the level of 48.23 ± 1.54 and 21.58 ± 2.34 g/l, respectively, and in two-year-olds — 32.42 ± 0.92 and 13,84 ± 0.61 g/l, respectively (p < 0.05). The activity of serum ALT in five-year-olds was 1.07 ± 0.06 μkat/l, and in two-year-olds — 0.85 ± 0.03 μkat/l (p < 0.01). Serum cholesterol in five-year-olds (3.94 ± 0.04 mmol/l) and two-year-olds (4.4 ± 0.08 mmol/l) did not differ significantly (p > 0.05). The content of serum triglycerides in five-year-olds (4.50 ± 0.49 mmol/l) and in two-year-olds (5.36 ± 0.45 mmol/l) did not differ significantly (p > 0.05). The study of carbohydrate metabolism revealed a pronounced variability in the glycemic index in the younger age group (coefficient of variation 44.7 %) with an average blood glucose value of 2.69 ± 0.31 mmol/l. The blood glucose content of five-year-olds was higher than that of two-year-olds — 3.84 ± 0.24 mmol/l (p < 0.05). The established parameters of variation and the age specificity of the indicators of the erythron system, protein, lipid and carbohydrate metabolism can be used to assess the state of physiological adaptation of the hybrid after wintering in cages in the Volga delta.

Natural and anthropogenic factors influence on the botanic natural sanctuary vegetation cover dynamics of the river Volga delta

The river Volga state assessment and landscape functioning is an extremely necessary part for stable and ecologically safe region development. One of the most important this assessment components is vegetation monitoring organization and conduction, which is the necessary part of modern ecosystem exploitation. Monitoring investigations brief results of the botanic natural monuments vegetation cover situated in the eastern part of the river Volga delta are shown in this work. Environment major factors change impact defining main ecological properties if deltoid landscape vegetation cover: some climatic characteristics, the river Volga hydrological regime changes and flooding conditions, vegetation cover differentiation peculiarities in dependence on deltoid land forms and confined processes to it are considered for the monitoring period. It was revealed during the monitoring that abrupt water-soluble salts amount increase in soils occurred, also toxicity level and soil salinization type from chloride- sulfate to sulfate-chloride, that affects vegetation cover: total biomass decrease, projective cover degree decrease on the all deltoid landscape high level, sedges and gramineous plant involvement degree decrease and herbs increase in vegetation cover due to ariditization degree and desert advancing caused either by natural or anthropogenic impact.

Physiological state of the sterlet × beluga hybrid (Asipenser ruthenus × Huso huso) when growing under ecological conditions in the Volga delta

Three-year-olds (15 individuals) and eight-year-olds (15 individuals) of the sterlet × beluga hybrid (Asipenser ruthenus × Huso huso), grown in mesh cages in the Volga delta, were studied in the third decade of September 2019 in order to establish the functional state of the organism by blood parameters reflecting the state erythron and metabolism. The results of the performed study found that the erythron system differs in a smaller number of blood erythrocytes in eight-year-olds (0,76 ± 0,04 × 1012l –1) compared with three-year-olds (0,98 ± 0,04 × 1012l –1), in the absence of differences in blood hemoglobin and serum iron. Analysis of the state of protein metabolism showed that the content of total protein and the activity of ASAT in serum were the same in the groups. The serum albumin content in eight-yearolds was 17,87 ± 0,92 g/l, which was significantly less than in three-year-olds (24,15 ± 1,78) (p < 0,05). The relative content of serum albumin (as a percentage of total protein) in eightyear-olds was 51,04 ± 3,12%, which is less than in three-year-olds (72,51 ± 6,04%) (p < 0.01). The serum ALAT activity in eight-year-olds was lower than in three-year-olds (2,33 ± 0,16 and 2,93 ± 0,17 μkat/l, respectively) (p < 0,05). The results of the study of lipid metabolism revealed that serum cholesterol in eight-year-olds (2,62 ± 0,11 mmol/l) is less than in three-year-olds (1,39 ± 0,05) (p < 0,05). However, the serum triglyceride content did not differ between threeyear-olds and eight-year-olds, being 3,50 ± 0,07 and 3,26 ± 0,13 mmol/l, respectively. The glycemic values in three-year-olds and eight-year-olds are significantly different and amount to 1,80 ± 0,08 and 1,42 ± 0,11 mmol/l, respectively (p < 0.05). The results of the study can be used to assess the state of physiological adaptation of the hybrid and to determine the reference values of the parameters of the erythron system and metabolic homeostasis.