Search Results (30)

The taxonomic composition and structure of invertebrate assemblages in five lakes from the Kulunda steppe, located in an arid region of southwestern Siberia (Russia), were studied. The lakes varied greatly in their total salinity (5 to 304 g L⁻¹) and carbonate alkalinity (0.03 to 4.03 mol-eq L⁻¹). The invertebrate fauna was characterized by low diversity. Only five taxa of macrozoobenthos and two taxa of planktonic invertebrates were identified. As water salinity increased, the taxonomic diversity of the studied lakes decreased, and at salinities > 276 g L⁻¹, monodominant assemblages were formed. The high numbers and biomass of aquatic organism provide a rich food supply for native and migratory waterfowl. The low taxonomic diversity of the invertebrate assemblages of the lakes makes them vulnerable to any negative external impact. The climate in the Kulunda steppe demonstrates a long-term aridization trend. If this continues in the future, then over time, this may lead to the gradual salinization of lakes and a further decrease in the taxonomic diversity of hydrobiological assemblages. This emphasizes the ecological importance of the studied territory and the necessity for its inclusion in the list of sites protected by the Ramsar Convention. Full article

At the end of the Pleniglacial and the first half of the Late Glacial period, approximately between 18 and 14 ka BP, rivers of the central and southern parts of the East European Plain had channels up to 10 times as large as the present day channels of the same rivers. These ancient channels, called large meandering palaeochannels, are widespread in river floodplains and low terraces. The hydrological regime of these large rivers is of great interest in terms of the palaeoclimatology of the late Marine Isotope Stage 2 (MIS 2). In this study, we aimed at quantitative estimation of maximum flood discharges of rivers in the Dnepr, Don and Volga basins in the late MIS 2. To approach this, we used massive measurements of the morphometric characteristics of large palaeochannels on topographic maps and remote sensing data—palaeochannel width, meander wavelength and their relationships with river flow parameters. The runoff depth of the maximum flood, which corresponds to the maximum depth of daily snow thaw during the snowmelt period, was obtained for unit basins with an area of <1000 km². The mean value for the southern megaslope of the East European Plain was 44.2 mm/day (6 times the modern value), with 46 mm/day for the Volga River (5.5 times), 45 mm/day (6.3 times) for the Don River and 39 mm/day (8 times the modern value) for the Dnepr River basins. In general, the Dnepr basin was drier than the Don and Volga basins, which corresponds well to the modern distribution of humidity. At the same time, the westernmost part of the Dnepr River basin was relatively wet in the past, and the decrease in humidity from the past to the modern situation was greater there than in the eastern and central regions. The obtained results contradict the prevailing ideas, based mainly on climatic modeling and palynological data, that the climate of Europe was cold and dry during MIS 2. The reason is that palaeoclimatic reconstructions were made predominantly for the LGM epoch (23–20 ka BP). On the East European Plain, the interval 18–14 ka BP is rather poorly studied. Our results of paleoclimatological and palaeohydrological reconstructions showed that the Late Pleniglacial and the first half of the Late Glacial period was characterized by a dramatic increase in precipitation and river discharge relative to the present day. Full article

In this study, spanning from 1938 to 2020, the hydrological changes in the Volga River and their repercussions on the Caspian Sea level were examined. Analysis reveals a correlation between high Volga River runoff and increased atmospheric precipitation in its basin. However, in recent years (2005–2020), a significant decline in the runoff coefficient at the Verkhneye Lebyazhie hydrological station, attributable to climate warming surpassing global temperature anomalies, has been observed. This warming’s impact on river flow and sea level was quantified, resulting in a 133 cm decrease in sea level from 1977 to 2020. Notably, while, historically, Caspian Sea level changes mirrored Volga River runoff fluctuations until 2005, since 2006, the sea level has markedly dropped, decoupling from river runoff variations. Comparison with recent studies suggests that altered wind characteristics over the Caspian Sea, influencing surface evaporation, may have significantly contributed to this rapid sea level decline in recent years. Full article

Knowledge of the historical and present dynamics of populations of migratory fish can promote our understanding of factors affecting their recruitment and abundance. Taxonomic identification of 23,802 bone remains and 13,539 scales of fish from 30 archaeological sites along Volga River revealed that they belonged to 41 different fish species. These data allow for retrospective comparisons and highlight the potential of archaeozoology in conservation biology. Sturgeons and salmonids are vulnerable to the impacts of fishery and climatic change. The sharp decline in the numbers of Starry sturgeon (Acipenser stellatus), Caspian trout (Salmo caspius), and Caspian Inconnu (Stenodus leucichthys) from the Volga in the 17th and 18th centuries was likely related to a cooling period (“Little Ice Age”). At present, the population numbers of all anadromous sturgeons and salmonids of the Volga River are critically low. In the Volga basin over the past two millennia, the sterlet (Acipenser ruthenus) has had a very large population number, high genetic (haplogroups and haplotypes) diversity, and large body sizes. Genetic analysis (aDNA and eDNA) have great potential to expand the knowledge of fish populations along large rivers and to improve long-term biomonitoring. Therefore, analyses of historical data, conventional surveys, as well as the inclusion of genetic approaches complement each other in the development of effective conservation strategies. Full article

In this paper, by using GNSS technologies, some features of the distribution and some morphometric parameters of dams and ponds created by the Eurasian beaver (Castor fiber L.) along ten rivers of the Volga-Kama region of European Russia were identified. Detected features depend on the geomorphological, lithological, and landscape features of these rivers and their basins. The significant role of river slopes, as well as landscape zoning, in the distribution of beaver dams and ponds along small rivers in the study region is shown. In the rivers under study, almost all beaver constructions are located on riverbed slopes of less than 3% (most often, less than 2%). In the south of the forest zone (the southern taiga of the Vyatka River basin), the majority of dams and ponds (about 90%) are located on slopes of less than 1%, while, within the uplands of the forest-steppe zone, this location varies depending on the length of the rivers. In general, the greater the average slope of the river (the greater the average elevation of the river basin), the lower, other things being equal, the degree of beaver transformation of such rivers. This feature is better expressed in the rivers of the forest landscape zone and less expressed in the rivers flowing in the forest-steppe zone. Analysis of the morphometric parameters of beaver dams shows statistically significant trends towards an increase in their average height, as the channel slopes increase. Statistically significant trends were also identified towards a decrease in the length of dams and the length of associated ponds, with an increase in channel slopes. It is noteworthy that the critical values of the slope for a statistically significant and relatively sharp change in these parameters are 1.45%, 1.07 (or 0.54)%, and 0.65 (or 0.47)%, respectively. The greatest average heights of beaver dams are confined to those rivers where their basins are composed of loamy rocks/soils (especially those that are poorly plowed), compared with “sandy” river basins. This may be due to the peculiarities of the ratio of surface and underground water runoff in these basins and, as a consequence, different intensities of snowmelt- and rainfall-induced flood flow. We assume that the above-mentioned features reflect the early stages of beaver expansion (population growth) in the studied rivers. Full article

The Volga River is the largest river in Europe in terms of basin area (1.36 mio. km²), length (3531 km), and water content (annual flow 254 km³). We conduct long-term water quality studies in the Volga headwaters: in the Upper Volga Lakes, the free-flowing section, as well as in the Ivankovskoye and Uglich Reservoirs. At the source of the river, the water is very soft, slightly mineralized, characterized by high color indicators (up to 400 degrees Pt-Co scale) and permanganate oxidation (60.3–72 mgO/L). In the Upper Volga Lakes, water mineralization increases to 110 mg/L, and the color of the water decreases significantly. In the Ivankovo Reservoir, higher concentrations of manganese and BOD₅ are noted than in the Volga above Tver. Based on total phosphorus concentrations, the Upper Volga Reservoir (Lake Volgo) and the free-flowing section of the Upper Volga (from Selizharovo to Tver) belong to the “mesotrophic” class, and the Ivankovskoye Reservoir belongs to the “eutrophic” class. We characterize the Volga headwaters based on physico-chemical parameters “balanced” and discuss the relevance of “natural pollution”. Especially the free-flowing section comprises an important reference section for lowland rivers; thus, long-term monitoring of abiotic and biotic aspects is an important issue. Full article

Increasing anthropogenic influence and climate change are leading to significant transformations in living conditions for indigenous representatives of aquatic communities. The problem of alien species invasions is actively discussed in the example of large rivers and water reservoirs, but medium and small rivers with weak anthropogenic influence have been insufficiently studied in this aspect. With the help of analysis of literary data and the results of our own long-term observations of phytoplankton using morphological and molecular genetic methods in some left-bank Volga tributaries, we identified six invasive species of different taxonomic groups of algae, with a predominance of diatoms. The relevance of using both traditional and modern approaches to identifying invasive algae species is revealed. Such invasive species as Thalassiosira incerta, T. faurii, Skeletonema subsalsum, Unruhdinium kevei, and Gonyostomum semen were part of planktonic communities; the benthic species Plagiotropis lepidoptera var. proboscidea sometimes reached a significant level of development (up 6 to 44% from total biomass) in plankton. It was demonstrated that some algae species have firmly taken the position of dominants and subdominants in planktonic algae communities. The expansion of alien representatives of microphytobenthos was noted in the Volga River basin for the first time. For Gonyostomum semen, its European origin was revealed, for plankton and benthic diatom—Ponto-Caspian. Our study showed that the processes of invasion and subsequent development of alien species take place in habitats with weak anthropogenic influence, which is likely determined by the hydrological, hydrochemical, and climatic changes in river basins and the high adaptive capabilities of invasive species. Full article

Although Eurasia’s Caspian basin once supported the world’s richest and most diverse complex of sturgeon species, recent human activities have decimated populations of these ecologically and economically important fish. All five anadromous Caspian sturgeon species are critically endangered, and the potamodromous sterlet is also threatened. The precipitous decline of these species is due to a combination of factors that includes illegal, unreported, and unregulated (IUU) fishing; destruction of feeding and spawning habitat; water pollution; and the environmental consequences of climate change. International efforts are currently underway to re-establish sustained naturally reproducing sturgeon populations in the basin. Here, we update and review the status of sturgeon in the Caspian Sea with emphasis on the northern basin and the inflowing Volga and Ural rivers. We then focus on efforts to restore sturgeon in the Ural, which originates in Russia and flows through Kazakhstan before entering the Caspian Sea. With nearly ideal hydrological conditions for sturgeon, the Ural is the basin’s sole remaining river that allows migrating sturgeon unimpeded access to potentially productive spawning grounds. The challenge of re-establishing sturgeon in the Ural River exhibits the classical characteristics of wicked problems: ambiguous definitions, changing assumptions and unanticipated consequences, tradeoffs and economic dependencies, an incomplete and contradictory knowledge base, and no straightforward pathway toward a final solution. This challenge is examined here for the first time from the perspective of its wicked dynamics, with consideration given to approaches that have proven effective elsewhere in resolving wicked environmental problems. Full article

This study investigated the species composition, distribution, and salinity tolerance of macrozoobenthos in 17 small rivers in the southern arid region of the East European Plain, which are characterized by a small channel gradient, slow-flowing or stagnant water bodies, and a wide range of water salinity, varying between 0.18 and 30 g L⁻¹. In total, 156 taxa were found, among which 66 were Diptera species. The study revealed that the formation of benthic communities in the rivers is influenced by natural factors of the catchment basins, including the flat landscape with sparsely developed relief differentiation, climate aridity, and the widespread occurrence of saline soils and groundwater, largely related to the sedimentation of the ancient Caspian Sea and modern climate changes. These conditions are favorable for the occurrence of lacustrine macrozoobenthic species in freshwater, euryhaline, and halophilic ecological groups. The investigation revealed a decrease in species richness in response to an increase in water salinity. The five identified halophilic species Tanytarsus kharaensis, Glyptotendipes salinus, Cricotopus salinophilus, Chironomus salinarius, and Palpomyia schmidti can be used as indicators of river ecosystem salinization. Full article

Despite the full attention of malacologists to the study of Corbicula clams, stimulated mainly due to their high invasive potential and unique breeding system, studies based on an integrative taxonomic approach to identify various invasive lineages of this genus in European Russia are still limited. Our fieldwork was conducted in the Don, Volga, and Caspian Sea basins. In total, four distinct morphotypes belonging to the European forms R, Rlc, S, and “Int” of Corbicula clams were distinguished. According to our molecular genetic data, two Corbicula lineages, relevant to the nominal species Corbicula fluminea and C. fluminalis, can be defined. We observed a discrepancy between mtDNA haplotypes and morphological features for all individuals that were sampled from the Don and Kura Rivers. Identified mismatch may be due to the androgenetic reproduction of Corbicula that leads to cytonuclear inconsistencies. The 28S rRNA polymorphism in C. fluminea and C. fluminalis from studied localities was recorded. This occurrence is perhaps due to hybridization events between forms R, S, and Rlc. The biogeographic origins of Corbicula invasive lineages are discussed. Corbicula fluminalis (FW17, form S) has been detected for first time in the native range, namely in Azerbaijan, Tajikistan, Turkey, and Myanmar. We assume that the invasion of C. fluminalis into reservoirs and watercourses of the Caspian Sea basin (Republic of Dagestan and Stavropol Krai of Russia) was from Western Asia and Transcaucasia, and the introduction of C. fluminea to the Don and Volga River basins was from unspecified European countries. Full article

Floods have always threatened the survival and development of human beings. To reduce the adverse effects of floods, it is very important to understand the influencing factors of floods and their formation mechanisms. In our study, we integrated the Gravity Recovery and Climate Experiment and its Follow-On and Swarm solutions to estimate an uninterrupted 19-year flood potential index (FPI) time series, discussed the spatiotemporal distribution characteristics of the FPI and monitored major floods in the Volga River basin (VRB) from 2003 to 2021. Finally, we analyzed the relationship between the FPI and hydrometeorological factors to comprehend the flood formation mechanism. The results show that data fusion has reduced the uncertainty of terrestrial water storage change (TWSC), and the TWSC from the combined satellite gravity observations has a good consistency with that from the Global Land Data Assimilation System model (correlation coefficient = 0.92). During the study period, two major floods (June 2005 and May 2018) occurred in the VRB. The FPI has a significant seasonal change characteristic, and shows a high flood risk in spring and a low one in autumn. With regards to spatial distribution, the flood risk is increasing in the north (increasing rate = 0.1) and decreasing in the south (decreasing rate = 0.39). Snow water equivalent (SWE, correlation coefficient = 0.75) has a stronger correlation with the FPI than precipitation (PPT, correlation coefficient = 0.46), which is attributed to the recharge of SWE on water resources greater than that of PPT. The rising surface temperature (ST) speeds up snow melt, resulting in excessive groundwater and soil moisture, and the flood risk greatly increases at this time. The process lasts about three months. Therefore, except for PPT, ST is also a climatic factor leading to the floods in the VRB. Our study provides a reference for flood research in high-latitude regions. Full article

The depressed river mussel Pseudanodonta complanata (Rossmässler, 1835) is an endangered freshwater bivalve with sparse distribution across Europe. Despite its high conservation priority, available data on the current population genetics and biogeography of P. complanata are very limited. In this paper, we studied the genetic diversity and differentiation of P. complanata based on newly sequenced COI and ND1 gene fragments, and on available sequences from the NCBI GenBank. We discovered a localized and highly divergent lineage in the Don River basin and a widespread but low diversified lineage distributed from the Volga River basin to the Oise River in France. A star-like haplotype network, results of mismatch analysis, and significant negative values of neutrality tests reveal that the pan-European lineage went through a bottleneck event. The discovery of the separate lineage in the Don River basin is and additional evidence of the existence of Pleistocene glacial refugia in the south of the Russian Plain. Moreover, this finding confirms the significance of the Azov Sea drainage as a freshwater biodiversity hotspot of great conservation importance. Full article

In this study, we present our dataset containing up-to-date information about occurrences of trematodes in small mammals in the Middle Volga region (European Russia). The dataset summarizes micromammals’ trematode occurrences obtained by long-term field helminthological studies of soricomorphs, erinaceomorphs, bats and rodents during a period of more than 20 years (1999–2022). Our studies of trematodes in micromammals were conducted using the method of complete helminthological necropsy. The dataset includes 7470 records of trematode occurrences in micromammals with 4483 digenean records in Samara Oblast, 2986 records in Republic of Mordovia and one trematode record in Ulyanovsk Oblast. Our dataset presents the data on 43 trematode species from 21 genera and 9 families found in the region studied. The data on trematodes from 28 species of micromammals belonging to 14 genera are presented. In total, the number of collected trematode specimens in our dataset is 153,050. Each occurrence record contains the trematode species name, basis of record, locality of finding, host species, site in host, date and authors of the record and species identification. All occurrence records are georeferenced. The dataset is based on the research of the staff of the Institute of Ecology of the Volga River basin of RAS and the Joint Directorate of the Mordovia Nature Reserve and National Park “Smolny”. The distribution and diversity of trematodes of small mammals in the Middle Volga region has not been completely studied, and further investigation may reveal both new occurrences of trematodes and new host records. Full article

When managing water resources in order to provide water to consumers, a number of consequences arise related to the violation of the hydrological regime due to the regulation of flow by reservoirs. The second factor is possible climate change. These changes can negatively (or positively) affect the functioning of aquatic ecosystems. To reduce the impact on the environment, it is necessary to determine the nature and indicators of changes in the hydrological regime, calculate quantitative estimates of these indicators and ranges of acceptable values, and develop release rules that ensure compliance with these ranges with a given probability. To manage the water resources of the Volga and Kama Rivers, the main ecological task is to flood the floodplain meadows, to maintain the conditions of natural reproduction of fish on the Lower Volga, including the Volga River delta and the Volga–Akhtuba floodplain. In addition, it is necessary to meet with sufficient reliability the requirements of energy in the summer–autumn and winter low-water periods and water transport during the navigation period. The task of optimal management is to find such solutions in years of different water content that ensure the well-being of the main water users with a given probability and do not disturb the Lower Volga ecosystem. This article presents the research of the water resources state of the water resource system of the Volga and Kama river basins. A statistical analysis of the hydrological series of the observed inflow for 1916–2020 was performed, and the inflow change point (1979) was found by the Bayesian method of estimation. A statistically significant difference between the average inflow values of two series (1916–1978, 1979–2020) was proved using a two-sample Student’s test. The seasonal parameters of the reliability curves were calculated based on the three-parameter Kritsky and Menkel distribution. For these two series, water resource optimization calculations (using Excel Solver) were performed, and the reliability of fulfilling the requirements of water users was determined; for the series 1916–1978, an alternative solution was found in favor of fisheries, and an analysis of the results was also performed. The methodology used in the research allows finding trade-off solutions in the favor of different water users (ecology, agriculture and fisheries, water supply, hydropower, navigation, etc.) and is based on the use of multi-criteria optimization methods and the trade-offs theory. As a result of the research, new knowledge was obtained about the hydrological situation in the basin of the Volga–Kama reservoir cascade in connection with climate change. Full article

We studied the trematode fauna in land birds from the Republic of Mordovia (European Russia) in 2018–2022. In total, we identified 16 digenean species in 45 species of birds from the orders Passeriformes, Piciformes, Caprimulgiformes and Falconiformes. The trematodes Phaneropsolus micrococcus and Morishitum polonicum were recorded for the first time in the birds’ parasite fauna of Russia. We obtained the first data on helminths in Hippolais icterina and Ficedula albicollis from Russia and in Coccothraustes coccothraustes from the Middle Volga region. New host records resulting from our study include Brachylaima mesostoma from Coccothraustes coccothraustes; Urogonimus macrostomus from Sylvia atricapilla, Ficedula albicollis, Ficedula hypoleuca and Acrocephalus palustris; Plagiorchis maculosus from Ficedula albicollis and Hippolais icterina; and Lyperosomum alaudae from Ficedula hypoleuca. The common parasite of rallid birds Leucochloridium holostomum is recorded for the first time from Turdus merula in Russia. Taking into account the newly obtained data, we carried out a review of trematodes in land birds of the Middle Volga region, of which the Republic of Mordovia is a part. Currently, the list of land bird digeneans in the Middle Volga region includes 56 species. Among all the studied land birds, members of the order Passeriformes have the richest trematode fauna (33 species). The diversity of trematodes found in passerines is due to the large number of both individuals and species studied and the variety of habitats and diet preferences of these land birds. Most of the identified trematode faunas (47 species) are obligate parasites of land birds. Nine species parasitize land birds accidentally and/or facultatively. In the Middle Volga area, the fauna of trematodes is the most diverse in land birds of the Nizhny Novgorod region, where 31 species are revealed. Fewer species of trematodes are identified in birds from the Bashkortostan (20), Mordovia (17) and Samara regions (15). For the birds of Chuvashia and Tatarstan, only eight and one species of trematodes are known, respectively. Six trematode species, found in land birds, have veterinary and medical significance as potential pathogens of dangerous helminthiases. Full article