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Over the entire period of studies in the water bodies in the Ural River basin, comprehensive hydrobiological studies have not been carried out in many areas both on the main watercourses of the Ural and Sakmara rivers and on a large number of tributaries of different levels. The results of such studies carried out by the Water Problems Institute, Russian Academy of Sciences, during expeditions in the summer and autumn 2022 are discussed. A large body of data on phytoplankton, zooplankton, zoobenthos, and juvenile fish was collected and processed. [ABSTRACT FROM AUTHOR]

During 2021–2023, the tropical oligochaeta Branchiura sowerbyi Beddard, 1892 was recorded at two stations in the Sheksna Reservoir. The finds of the individuals of different size suggest successful reproduction of the species in the Sheksna Reservoir. The success of naturalization of this species may be related to climate warming. The detection of B. sowerbyi in this reservoir occurred against the background of a five-year increase in water temperature indices. A tendency for B.sowerbyi spreading northwards was noted. [ABSTRACT FROM AUTHOR]

To compare trophic properties in pelagic and benthic communities of the Kara Sea, isotopic composition of carbon and nitrogen (δ13C and δ15N) was examined in tissues of zooplankton, zoobenthos, and fish. The organisms exhibited rather low δ13C values in the surveyed area. Because of stable difference in isotopic composition of carbon for zooplankton and zoobenthos, the pelagic and benthic communities could be separated by the level δ13C = –21.5 ‰, on average. The δ15N values for these communities varied within their 3 trophic levels in the range from 6.4 ‰ (for bivalve Serripes groenlandicus) to 16.3 ‰ (for lycod Lycodes seminudus), reflecting the input of predation. The bottom and pelagic communities in the Kara Sea demonstrated trophic interdependence. Both pelagic and bottom fish species, more or less, consumed both pelagic and benthic prey. Taking into account the content of 13C isotope in tissues of zooplankton and zoobenthos, about 40 % of the bottom nekton species were linked mainly with the pelagic food web and bypassed the benthic one. Pelagic fish fed mainly on pelagic prey, though the portion of zoobenthos in food of the dominant species — arctic cod had increased with the fish size increasing. On the contrary, the portion of zoobenthos in food of ruffed flounder had decreases with their size.

Purpose. Analysis of obtained data and integration of previous hydroecological data and statistical information for the preparation of scientific and biological rationale and development of the regime for rational and environmentally sustainable fishery exploitation of the Khrystoforivske Reservoir. Methodology. Hydrochemical and hydrobiological methods of sampling, laboratory and statistical processing of the material were used in the water area of the Khrystoforivske reservoir of the Bokovenka river during comprehensive studies in the summer of 2022. We studied the hydrochemical parameters of the water body, species composition, quantitative parameters of the main groups of hydrobionts, including fish forage organisms (macrophytes, phytoplankton, zooplankton, zoobenthos), the biological productivity of the reservoir was measured based on the main groups of hydrobionts. To determine the state of the main groups of hydrobionts, two samples of phytoplankton, zooplankton and zoobenthos were collected. Macrophytes were studied, water samples were taken from different parts of the water body for hydrochemical analysis. The biomass of phytoplankton was calculated based on the biomass of standard volumes of algae, the biomass of zooplankton – by multiplying the quantity of organisms by their individual weights, zoobenthos – by weighing individual groups of hydrobionts on torsion scale and recalculating and summing up. The reservoir feeding capacity was assessed by the quantitative development of zooplankton according to known classifications. Findings. The main parameters of the chemical composition and properties of the water of the Khrystoforivske reservoir, which condition the bioproductivity and fish farming performance, were determined: pH, content of dissolved gases, organic substances, biochemical demand of O2, nutrients content, as well as general mineralization and hardness, concentration of the major ions. According to the hydrochemical classification, water is bicarbonate type II and is referred to fresh water. The degree of water saturation with easily-oxidizable organic matter has decreased over the past 15 years and is within standards for aquaculture. Considering all environmental and sanitary parameters, water of the Khrystoforivske reservoir is characterized by fair or average quality, it is eupolytrophic. The water characteristics indicate that the fishery exploitation at the reservoir during previous Special Commodity Fish Farming Regimes (SCFF) (1996–2021) has produced no adverse effects on the general ecological and sanitary condition of water. Aquatic phytocoenoses of the Khrystoforivske reservoir are represented by associations of submerged and aerial-aquatic plants, with a total area of 5.2 hectares. The total production of aquatic plants is 36.245 tons. The phytoplankton of the reservoir includes 51 species of algae (six groups). In terms of quantity, small-celled Cyanoprokaryota predominated (about 70%). Diatoms, green and euglenic algae dominated in biomass. In 2022, the average biomass of phytoplankton in the Khrystoforivske reservoir was up to 1.80 g/m3, the total annual production of phytoplankton reached 201.06 tons. In total, 16 species of organisms have been identified in the zooplankton of the reservoir: Rotatoria, Cladocera and Copepoda. The average abundance of zooplankton in the reservoir was 31,390 ind./m3, and its average biomass reached 0.41 g/m3. The value of primary production of zooplankton is 123.9 kg/ha, and the total stock in the reservoir is 7.687 tons. The fish food supply in terms of zooplankters in the Khrystoforivske reservoir are low. The reservoir itself, based on the group of zooplankton, can be referred to fishery class III (the lowest class). The bottom fauna is represented by 40 taxonomic groups of invertebrates. The Chironomidae and Oligochaeta assemblies are most developed in terms of density, but molluscs dominate in biomass. There is a general trend towards a decrease in the quantitative parameters of macrozoobenthos, in particular, Mysidacea. The average biomass of soft benthos (2.17 g/m2) and the average biomass of the entire zoobenthos (33.62 g/m2) indicate that the reservoir preserves its fishery potential due to macrozoobenthos. The primary production of zoobenthos of the Khrystoforivske reservoir is 130.2 kg/ha. The total stock of zoobenthos is up to 8.072 tons. The values of the fish food supply are quite high due to zoobenthos in the reservoir, the water body in terms of benthos biomass is referred to fishery class II (medium productive reservoirs). The obtained comprehensive data on the food supply of the Khrystoforivske reservoir indicate the availability of sufficient bioproduction potential for its continuous effective fish-farming on the basis of the special commodity fish farming regime. Originality. For the first time in the last 10 years, comprehensive data on the food supply of the Khrystoforivka reservoir, which is used in special commodity fish farming regime (SCFF), have been obtained and analysed. Practical value. The results obtained are of practical importance for the development of scientific and biological rationale for fish farming in the Khrystoforivske Reservoir.

Despite the increasing water and sediment pollution in the western part of the Northern Caspian Sea, the quality of its marine environment has never been assessed through bioindication, largely due to methodological issues. In this article, the method of standards, which involves comparing the species composition between the polluted and clean (reference) sites, was used for the bioindication of organic pollutants in the Northern Caspian Sea. The study area was segmented based on isobaths. The segments were determined depending on the range of depths inhabited by zoobenthos species and their ecological valence to oxygen. The depths with a sufficient abundance of oxyphilic zooplankton species (bioindicators) to apply the method of standards were located. The obtained results show that the method of standards is a good and reliable choice to assess the marine environment quality in the Northern Caspian Sea at isobaths of 6–9 m and within depths of 14–18 m for polluted and reference sites. However, the sediments must contain shells, sand, and siltstones. Therefore, while the method of standards has clear merits, it does not suffice for the rest of the Caspian Sea area.

Lynceus brachyurus was first discovered in the highland wetland of Armenia. This finding not only contributes to our understanding of the geographic distribution of Lynceus brachyurus but also sheds light on the ecological preferences and adaptability of this species to diverse habitats.

Purpose. Analysis of obtained data and integration of previous hydroecological data and statistical information for the preparation of scientific and biological rationale and development of the regime for rational and environmentally sustainable fishery exploitation of the Khrystoforivske Reservoir. Methodology. Hydrochemical and hydrobiological methods of sampling, laboratory and statistical processing of the material were used in the water area of the Khrystoforivske reservoir of the Bokovenka river during comprehensive studies in the summer of 2022. We studied the hydrochemical parameters of the water body, species composition, quantitative parameters of the main groups of hydrobionts, including fish forage organisms (macrophytes, phytoplankton, zooplankton, zoobenthos), the biological productivity of the reservoir was measured based on the main groups of hydrobionts. To determine the state of the main groups of hydrobionts, two samples of phytoplankton, zooplankton and zoobenthos were collected. Macrophytes were studied, water samples were taken from different parts of the water body for hydrochemical analysis. The biomass of phytoplankton was calculated based on the biomass of standard volumes of algae, the biomass of zooplankton - by multiplying the quantity of organisms by their individual weights, zoobenthos - by weighing individual groups of hydrobionts on torsion scale and recalculating and summing up. The reservoir feeding capacity was assessed by the quantitative development of zooplankton according to known classifications. Findings. The main parameters of the chemical composition and properties of the water of the Khrystoforivske reservoir, which condition the bioproductivity and fish farming performance, were determined: pH, content of dissolved gases, organic substances, biochemical demand of O2, nutrients content, as well as general mineralization and hardness, concentration of the major ions. According to the hydrochemical classification, water is bicarbonate type II and is referred to fresh water. The degree of water saturation with easily-oxidizable organic matter has decreased over the past 15 years and is within standards for aquaculture. Considering all environmental and sanitary parameters, water of the Khrystoforivske reservoir is characterized by fair or average quality, it is eupolytrophic. The water characteristics indicate that the fishery exploitation at the reservoir during previous Special Commodity Fish Farming Regimes (SCFF) (1996-2021) has produced no adverse effects on the general ecological and sanitary condition of water. Aquatic phytocoenoses of the Khrystoforivske reservoir are represented by associations of submerged and aerial-aquatic plants, with a total area of 5.2 hectares. The total production of aquatic plants is 36.245 tons. The phytoplankton of the reservoir includes 51 species of algae (six groups). In terms of quantity, small-celled Cyanoprokaryota predominated (about 70%). Diatoms, green and euglenic algae dominated in biomass. In 2022, the average biomass of phytoplankton in the Khrystoforivske reservoir was up to 1.80 g/m³, the total annual production of phytoplankton reached 201.06 tons. In total, 16 species of organisms have been identified in the zooplankton of the reservoir: Rotatoria, Cladocera and Copepoda. The average abundance of zooplankton in the reservoir was 31,390 ind./m³, and its average biomass reached 0.41 g/m³. The value of primary production of zooplankton is 123.9 kg/ha, and the total stock in the reservoir is 7.687 tons. The fish food supply in terms of zooplankters in the Khrystoforivske reservoir are low. The reservoir itself, based on the group of zooplankton, can be referred to fishery class III (the lowest class). The bottom fauna is represented by 40 taxonomic groups of invertebrates. The Chironomidae and Oligochaeta assemblies are most developed in terms of density, but molluscs dominate in biomass. There is a general trend towards a decrease in the quantitative parameters of macrozoobenthos, in particular, Mysidacea. The average biomass of soft benthos (2.17 g/m²) and the average biomass of the entire zoobenthos (33.62 g/m²) indicate that the reservoir preserves its fishery potential due to macrozoobenthos. The primary production of zoobenthos of the Khrystoforivske reservoir is 130.2 kg/ha. The total stock of zoobenthos is up to 8.072 tons. The values of the fish food supply are quite high due to zoobenthos in the reservoir, the water body in terms of benthos biomass is referred to fishery class II (medium productive reservoirs). The obtained comprehensive data on the food supply of the Khrystoforivske reservoir indicate the availability of sufficient bioproduction potential for its continuous effective fish-farming on the basis of the special commodity fish farming regime. Originality. For the first time in the last 10 years, comprehensive data on the food supply of the Khrystoforivka reservoir, which is used in special commodity fish farming regime (SCFF), have been obtained and analysed. Practical value. The results obtained are of practical importance for the development of scientific and biological rationale for fish farming in the Khrystoforivske Reservoir. [ABSTRACT FROM AUTHOR]

This article examines the conditions for the formation of the hydroecological regime of the Ivankov Reservoir according to data from complex hydrological, hydrochemical, and hydrobiological surveys carried out in August 2020−2022. The differences in hydroecological characteristics are associated with the peculiarities of weather conditions in the summer seasons. Despite the significant flow of the reservoir, in its bottom layer during prolonged hot weather, the formation of oxygen-free conditions is possible, affecting exchange processes with the bottom, hydrobionts, and methane emissions. The increased bioturbation of bottom sediments (BSs) by benthos under oxygen deficiency activates metabolic processes at the water–BSs boundary, including the release of methane. A strong "bloom" of the reservoir, characteristic of hot weather conditions in 2022, led to a reduction in the specific flux of methane from the surface due to its oxidation with an excess of oxygen in the surface layer. [ABSTRACT FROM AUTHOR]

The paper examines the influence of seasonal ice and prevalent type of recharge on the formation and functioning of zoobenthos communities in the coastal shallow zone of water bodies located north of 35° N. It was revealed that in the coastal shallow zone, zoobenthos species do not form communities but are represented by seasonal ephemeral groups. These habitations reach the maximum species diversity and qualitative development in July. Recommendations are given on the frequency of zoobenthos sampling to determine the water quality and an ecological status of a water body. [ABSTRACT FROM AUTHOR]

Changes in the macrozoobenthos of two northern lakes differing in degree of humification of water over the 50-year period that have passed since the first studies were considered. In the lake with water uncolored by humus, the benthos biomass increased, and in the humified one, it decreased. The changes that have occurred are due to climate warming, especially pronounced in winter. It was concluded that even closely located bodies of water can respond differently to climate change. Depending on the nature of the catchment area and the morphology of the lakes, either an increase in their productivity due to the supply of nutrients or a decrease due to humification can be observed. [ABSTRACT FROM AUTHOR]

In 2018, a total of 45–57 zooplankton and 23–81 benthos taxa, as well as 0–6 alien zooplankton and 3–7 invasive zoobenthos species were found in different parts of the water area of the Gulf of Finland adjacent to St. Petersburg. From 2014 to 2018, aboriginal zooplankton and zoobenthos communities in the studied area remained relatively unchanged, while the populations of invasive species changed significantly. The range of some alien planktonic species extended to the east, i.e. to the Neva Bay, which could be due to their transfer from the adjacent areas of the Gulf of Finland. As compared to 2014, in 2018, a smaller number of invasive species in zoobenthos (only 10 species versus 14), as well as a significant reduction in the range or abundance of some invasive benthic species were recorded.

In order to understand the existing status of aquatic resources in the intersection of Nanla River and Kunmo Expressway and the impact of the bridge construction on aquatic organisms, this study carried out a resource survey in this river section. 57 species of 6 phytoplankton were detected in 3 sites, with the most Bacillariophyta, 27 species, showing a clear river phase; 26 species of zooplankton, with Protozoa and Rotifera taking the absolute advantage; 34 species of zoobenthos, with the most frequent species being Macrobrachium nipponense and Radix sp.; 26 species of fish in 5 orders and 12 families were collected, with Cypriniformes accounting for the majority of fish and Cyprinoidea being the main fish, accounting for 82. 35% of this order. The fish in the Nanla River basin are mainly sedentary indigenous fish, which mostly lay sticky and sinking spawns and have rich diversity. The survey results show that the construction of the bridge at the intersection of the Nanla River and the Kunmo Expressway will have a local impact on aquatic organisms, but does not affect the diversity of fish communities more. However, it is still necessary to continue to monitor the ecological environment of the protected area waters to provide scientific basis for future fish stocking in the protected area. [ABSTRACT FROM AUTHOR]

In the summer of 2014, a field study was carried out in four coastal rocky bottoms from the southeast coast of Spain. In this region, dense canopies of Ericaria mediterranea characterize the undisturbed areas and cover much of the infralittoral stage. Turfs composed of the coralline algae Ellisolandia elongata replace the canopy in places where any anthropogenic disturbance occurs. The main objective of this study was to compare the peracarid fauna inhabiting within the two types of phytal substrate, and to conduct several statistical analyses to detect significant differences between the two assemblages. Contrary to expected, the analyses showed that in E. elongata there was a higher population density of peracarids, as well as higher species richness and values for α-diversity indexes. However, none of these differences was statistically significant, although site-to-site comparison indicated greater differences between locations with the same physical cover. The data pointed out that the assemblage that inhabits the coralline turfs in the area was not an impoverished version of that found in pristine locations, so these algae can act as a suitable habitat for peracarids in case of mild human disturbance. [ABSTRACT FROM AUTHOR]

The bottom communities of the nearshore zone of the Valaam archipelago (Lake Ladoga) have been investigated. The stations were located in the littoral, sublittoral, and profundal at depths of 1–25 m. Three regions with different characteristics of the coast shore and relief were researched. A sampler-syringe was used to collect benthos, because it works the whole of grounds variety in the nearshore. The quantative characteristics of the bottom communities had been optimally described with the depth ranges. The wave activity significantly affected only the numbers of zoobenthos in the upper 10 m. The openness of the bay had a greater influence on the abundance and biomass of benthos in the range of 1–10 m, presumably taking into account the influence of reflected waves. The biggest numbers and biomass of zoobenthos were in the littoral of the close bay. In the semiclose bay and on the open coast, the maximum abundance of benthic invertebrates shifted in the sublittoral (depth >8 m), where waves affected the benthic communities less. The types of ground significantly affected only the taxonomical composition. In general, the preferential effect on the quantity characteristics of benthos on the rocky slope zone had the features of a shore (openness and depth patterns). These data can be used for inspections of the next influences on the nearshore benthic community and for analyzing and modeling the commercial resources and their forage base. [ABSTRACT FROM AUTHOR]

The results of a complex hydrochemical and hydrobiological study of salt lakes in southeastern Transbaikalia during the period of moisture change are presented. The studied lakes, according to geochemical classification, are chloride and soda types. The taxonomic diversity of aquatic biota decreases, while the salinity increases and the hydrochemical type of lakes changes from soda oligo-mesohaline (4–16 g/L) to chloride eu-hyperhaline (33–70 g/L) and soda hyperhaline (128–231 g/L). In soda oligo-mesohaline and chloride lakes, the phytoplankton taxonomic composition is similar and is represented by green and diatom algae, as well as cyanobacteria. Submerged aquatic plants are represented by Stuckenia pectinata in soda oligo-mesohaline lakes. Ruppia maritima is found in the Dabasa-Nor chloride lake. In zooplankton and zoobenthos, rotifers and chironomids dominate respectively. Quantitative characteristics of phytoplankton in oligo-mesohaline lakes are lower than in hyperhaline soda and eu-hyperhaline chloride lakes. The phytomass of submerged aquatic plants, on the contrary, is higher in oligo-mesohaline lakes. In the hyperhaline soda lake Borzinskoye, zoobenthos and zooplankton organisms are represented by planktonobenthos species, namely Anostraca, with low abundance. [ABSTRACT FROM AUTHOR]

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This study aimed to describe the distribution and diversity of soft bottom mollusk community in the Syrian transitional region and to assess the state of alien species in the northern part of the Syrian coast north of Latakia (Ibn Hani site) since 2010, at depths ranging between 110- 160 m. Sixty benthic samples were collected monthly using a Van-Veen grab 1/40 m2 . Water temperature, salinity, pH, and dissolved oxygen of the subsurface water were measured. Molluscan specimens were isolated and identified at the species level. The abundance and biomass for each species in the samples and per square meter were considered to assess spatial and temporal variation of Molluscan assemblages between depths within the months. A total of 167 mollusk species belonging to 3 classes were identified, 57 newly recorded in Syria, and 18 (10.7%) non-indigenous species were found. Among these, three new aliens of Retusa truncatula, Styloptygma beatrix, and Afrocardium richardi were recorded for Syria. The presence of these mollusks was associated with the soft sediments (mud), which did not differ by time or depths. The results revealed that the Molluscan community was dominant by Bittium arenarium, B. tarentinum, Odostomia lorioli, Turritella turbona, Varicorbula gibba, Nucula nucleus, and Lembulus pella. A significant decrease in biomass is expected due to overfishing and severe nutrient deficiency. Our study adds a large number of mollusks to the list of previously recorded species and confirms the increase in the number of aliens and the expansion of their spread in the medium depths. Greater efforts are required to detect more aliens and evaluate their progress, spread, and their relationship with natives, especially in harbors and port environments. [ABSTRACT FROM AUTHOR]

This study aimed to determine the water quality classes of seven rivers in the North Aegean Basin (Türkiye) according to their benthic macroinvertebrate groups. In order to determine water quality levels, water and benthos samples were taken from 17 localities in May and June 2014, and the collected material was examined. As a result, a total of 22,348 benthic macroinvertebrate individuals belonging to 47 taxonomic groups were identified. The main groups and individual numbers were as follows: Chironomidae (8948 ind.), Baetidae (3910 ind.), Oligochaeta (1715 ind.), Gammaridae (1667 ind.), Potamanthidae (1401 ind.), Asellidae (1113 ind.), Melanopsidae (968 ind.), Physidae (618 ind.), Dugesiidae (475 ind.) and Hydropsychidae (107 ind.). The relationships between benthic macroinvertebrates and environmental variables were examined by canonical analysis. The dominance, BMWP (Biological Monitoring Working Party) and ASPT (Average Score Per Taxon) indices among benthic invertebrate groups were calculated. The dominant group was Chironomidae with ~ 40%. Considering the BMWP scores, stations S2, S3, S12 and S17 were classified as polluted, station S5 was classified as unpolluted. ASPT scores indicated that station S3 was heavily polluted and S16 was the cleanest station. [ABSTRACT FROM AUTHOR]

Background. The article considers a special type of reservoirs – partially regulated sections of riverbeds and streams formed by hydraulic structures and other artificial obstacles on the example of the Nadezhdinskiy reservoir on the Truev river in Penza region. The purpose of this work is to assess the fish productivity of a pond-type riverbed water-lifting reservoir based on a forage base, ichthyofauna in comparison with the natural riverbed and to determine methods of its fisheries use. Materials and methods. Fisheries research at the Nadezhda reservoir and the Truev river was carried out in August 2017. The selection and processing of hydrobiological and ichthyological samples was carried out according to generally accepted methods used by us in the last decade in small watercourses and reservoirs of the Volga region. Results. The regulated section of the Truev river, referred to as the Nadezhda reservoir, is 8–53 times higher in terms of phytoplankton, zooplankton and zoobenthos biomass than the natural riverbed. Also, the ichthyomass in the reservoir is 4.7 times higher than in the river, in which there were no commercial fish species in the studied area. Fish productivity for the most demanded components of the feed base by local fish species in the Nadezhdinskiy reservoir amounted to 166 kg/ha, in the natural channel of the Truev river – 11 kg/ha. The potential fish productivity may be 115 kg/ha and 13.2 kg/ha, respectively. In general, the total fish productivity differs by 12 times. Due to such high productivity, the Nadezhdinskiy reservoir can be used for sports and amateur fishing, pasture or commercial fish farming. Conclusions. The pond-type water-lifting reservoir is characterized by fish productivity at the level of average indicators of fish ponds and reservoirs of complex purpose in Penza region and the Republic of Mordovia. Channel water-lifting reservoirs should be taken into account in the fund of pond fishing in the region and actively exploited, which will significantly increase the volume of aquatic biological resources in low-water regions.

The features of the structural characteristics of benthic communities were analyzed in five low-mountain watercourses of Altai in the areas located upstream and downstream populated areas. In some watercourses, a decrease of the frequency of occurrence of the most sensitive species, of the species richness of EPT taxa, and of the Shannon diversity index was noted in areas located downstream of populated areas compared to those upstream. A deterioration in the water quality of the Saidys River downstream the Sredniy Saidys village (down to the class of “moderately polluted”) and that of the Ulaushka River within the city of Gorno-Altaisk (down to the class of “polluted”) was revealed. It is recommended to use the EPT and BMWP indices to assess the ecological state of lowmountain watercourses of Altai based on macroinvertebrates.

The paper deals with monitoring results of phytoplankton, zooplankton and zoobenthos of the Sheksna reservoir, lakes Kubenskoye and Vozhe in Vologda Oblast in 2018–2022. The highest biomass of algae was recorded in lake Beloye (10.1 g/m3 ). In other water bodies, the average biomass made up 6.3–7.3 g/m3 . Diatom and cyanobacteria dominated in phytoplankton: diatom number was maximum in the river part of the Sheksna Reservoir, while cyanobacteria – in lake Beloye. Highly abundant Aphanizomenon flos-aquae induced annual water bloom of lake Beloye. Density of zooplankton was the greatest in Vozhe (131 thous. ind./m3 , 3.5 g/m3 ). Similar average biomass of zooplankton was noted in different parts of the Sheksna Reservoir (2.0 g/m3 ). In lake Kubenskoye, biomass reached 0.9 g/m3 . Copepoda formed the base of zooplankton number and cladocera – of biomass. In contrast to lake Vozhe (2.6 g/m2 ), zoobenthos in lake Kubenskoye was highly abundant (7.6 g/m2 ). The average biomass of zoobenthos in the Sheksna Reservoir accounted for 4–5 g/m2 . The dominant complex of zoobenthos included oligochaeta Limnodrilus hoffmeisteri, Tubifex newaensis, T. tubifex in all water bodies; chironomid larvae Chironomus sp., Procladius sp. – in the open sites; chironomids Endochironomus albipennis, Glyptotendipes gripekoveni, Cricotopus gr. sylvestris – in thickets. Chironomidae dominated in the Sheksna Reservoir and lake Vozhe, oligochaeta – in lake Kubenskoye.

Results of a study of Lake Tolpanjärvi's ecosystem are reported. Its hydrological and geochemical indices, as well as the current condition of biotic communities (the zooplankton, benthos, and fish population), were studied and analyzed. Analysis of the chemical composition of water indicates that the lake has a low organic-matter content (total phosphorus 0.007 mg/L, nitrogen 0.26 mg/L). Lake Tolpanjärvi is an oligotrophic lake, as indicated by the abundance of zooplankton (with a biomass of less than 1 g/m3) and zoobenthos (biomass 0.44 g/m2). The lake is of an oligosaprobic class (second-quality class, clean natural water), as evidenced by its saprobity index estimated using the Pantle–Buck method. The quantitative indices of the zoobenthos varied from 120 individuals/m2 and 0.08 g/m2 in the profundal zone to 1200 inds./m2 and 0.86 g/m2 in the quiet littoral zone. The lake is more similar in the chironomid index (K 2.10) to clean natural water. It is inhabited by eight fish species of five families. The fish population is dominated by the whitefish Coregonus lavaretus, the perch Perca fluviatilis, and the roach Rutilus rutilus. Two ecological forms of whitefish, differing in both the number of gill rakers (sparsely rakered 18–24 and medium-rakered 28–36) and biological indices (size–weight, maturation, fertility, and feeding), occur in the lake. Stable highly diverse ecosystems were shown to form the basis for the preservation of the gene pool and for assessment of the current condition of water bodies heavily affected by human activities. [ABSTRACT FROM AUTHOR]

Simple Summary: This investigation delves into the intricate world of aquatic life, specifically zoobenthos, and how they respond to a combination of environmental challenges: climate change, eutrophication, and pesticide contamination. These organisms play a vital role in aquatic ecosystems, affecting energy flow, nutrient cycling, and sediment decomposition. Unfortunately, these challenges have led to a decline in their numbers and changes in community structure. Notably, the warmer temperatures associated with climate change promote the abundance and diversity of zoobenthos while making these communities more similar across different sites. Pesticides like imidacloprid negatively impact the survival and growth of zoobenthos. Interestingly, when combined with warming, imidacloprid seems to mitigate its adverse effects, increasing species diversity. However, when nutrient loading is part of the equation, imidacloprid negatively affects species diversity. These findings reveal the intricate responses of zoobenthos to multiple stressors, offering valuable insights for ecosystem conservation and management. In simpler terms, this study explores how tiny underwater creatures react to a changing environment, which has consequences for our ecosystems. Multiple stressors, including climate change, eutrophication, and pesticide contamination, are significant drivers of the decline in lake zoobenthos. Zoobenthos play a crucial role in aquatic ecosystems, impacting energy dynamics, nutrient cycling, and sediment degradation. However, these stressors have led to a decrease in the abundance and diversity of zoobenthos, resulting in notable changes in species composition and structure. Eutrophication typically increases zoobenthos abundance while reducing taxonomic diversity. Climate change, such as warming and heatwaves, also affects the zoobenthos community structure, with different species exhibiting varying levels of adaptability to temperature changes. Additionally, pesticides like imidacloprid have negative effects on the survival and growth of zoobenthos. However, the interactions between imidacloprid and other stressors remain understudied. Here, we used 48 mesocosms (2500 L) to simulate shallow lakes. We combined nutrient loading, sustained warming, and the imidacloprid pesticide to test how these stressors interactively influence the survival and community of zoobenthos. The experimental results demonstrate that elevated temperatures have a significant impact on aquatic benthic organisms under different treatment conditions. The increase in temperature led to a notable rise in species richness and α-diversity, primarily attributed to the stimulation of metabolic activities in zoobenthos, promoting their growth and reproduction. This finding underscores the potential influence of climate change on aquatic benthic ecosystems, particularly in terms of its promoting effect on α-diversity. However, it is essential to note that elevated temperatures also reduced β-diversity among different sites, implying a potential trend toward homogenization in zoobenthos communities under warmer conditions. Moreover, this study revealed the interactive effects of multiple stressors on the diversity of aquatic benthic communities. Specifically, the pesticide imidacloprid's impact on zoobenthos is not isolated but demonstrates complex effects within various treatment interactions. In the presence of both temperature elevation and the addition of imidacloprid, the presence of imidacloprid appears to counteract the adverse effects of temperature elevation, resulting in increased species diversity. However, when imidacloprid coincides with nutrient input, it significantly affects α-diversity negatively. These findings highlight the complexity of zoobenthos responses to multiple stressors and how these factors influence both α-diversity and β-diversity. They provide valuable insights for further research on the conservation and management of ecosystems. [ABSTRACT FROM AUTHOR]

This article presents the results of a comprehensive hydrochemical and hydrobiological study of 13 different types of lakes in Transbaikalia conducted in July 2022. Based on factor analysis of hydrochemical and hydrobiological indicators, the lakes were divided into three groups: 1) brackish soda; 2) chloride and sulfate, as well as one salty soda lake, Shvartsivskoe; and 3) brine soda. It has been established that the number of species of different groups of aquatic organisms decreases as the salinity level increases, regardless of the chemical type of water. It has been shown that the dominant composition of primary producers in lakes of different types differs. Two new species of macroalgae for Transbaikalia have been identified (Stigeoclonium flagelliferum Kütz. and Rhizoclonium riparium: (Roth.) Harv.). In the flora of aquatic plants of Baikal Siberia, after more than a 100-year hiatus, Ruppia maritima L is present. The zooplankton of lakes is dominated by halotolerant species. The dominant structure of zoobenthos in brine and salt lakes is dominated by Artemia crustaceans and Ephydridae flies. In deeper brackish lakes, Chironomidae mosquitoes are always the dominant species. Quantitative indicators of phytoplankton and zooplankton communities are characterized by an inverse relationship. With the massive development of cryptophyte algae in brine reservoirs, the abundance and biomass of zooplankton are minimal. No significant fluctuations in the biomass of zoobenthos and phytomass of aquatic plants were detected. In sulfate and chloride lakes, the trophic structure of heterotrophs is represented in zooplankton by a grazing chain, and in zoobenthos by detritivores. [ABSTRACT FROM AUTHOR]

The taxonomic composition and quantitative characteristics of zooplankton and zoobenthos of several water bodies of natural origin have been studied in the Norilsk industrial region and adjacent territories a year after a technogenic accident. All age groups of most invertebrate species have been recorded at most sampling sites. Slightly disturbed watercourses are registered in the source of the Pyasina River and in the Daldykan River, located upstream the confluence of the Bezymyanny stream. These water bodies may serve as the background reservoirs for organizing restoration activities accompanied by an assessment of the ecological well-being of planktonic and bottom fauna of freshwater ecosystems. [ABSTRACT FROM AUTHOR]

The Angara River is one of the largest rivers in Siberia, overregulated by large reservoirs. Reservoir operation entails a change in the habitat for the river biota, as a result of which organisms with high environmental adaptability and resistance to pollution take the leading positions. Only if there is a detailed knowledge of the Angara aquatic life in modern conditions, it will be possible to carry out scheduled activities for the reconstruction of aquatic fauna and fisheries in connection with hydraulic engineering. Nowadays, there is a significant gap in hydrobiological studies of the unregulated lower section of the Angara. The work objective is to identify changes in the bottom fauna of the lower Angara section after the regulation of the Boguchanskaya HPP. In 2015, Boguchanskaya HPP reached the design production level. Samples of zoobenthos were collected in 2015 and 2022. Benthic fauna was studied in the lower reaches of the Angara River at a site of 436 km below the Boguchanskaya HPP dam on both river banks at depths up to 1,5 m. The collection and office analysis of the material were carried out according to generally accepted methodological recommendations. Zoobenthos biotopes are represented by pebble-sandy soil with varying degrees of siltation and macrophytes. The benthic fauna was gammarid-chironomid in nature. In 2022, compared with 2015, an increase in species composition was revealed due to chironomids; on the contrary, the number of species of mayflies and caddis flies decreased. The structural organization of communities changed: there was an increase in the proportion of chironomids and a decrease in the proportion of mayflies, caddis flies and mollusks. The number of chironomids increased by 4 times, and amphipods doubled. The number of caddis flies decreased by about 5 times, mollusks – by 3 times, and mayflies – by 12 times. At the same time, the total number of benthic fauna increased slightly – only by 1.5 times. Currently, the number of benthic fauna is 2,9 thous ind/m2, biomass is 14,6 g/m2. The general trend of the revealed changes is aimed at increasing the number of tolerant bentonts (chironomids and amphipods) and reducing indicator taxa sensitive to pollution (mayflies, stoneflies, caddis flies and mollusks). The reason for the transformation of bottom communities is the cascade regulation of the river. The Boguchanskiy reservoir, which closes the cascade, is the recipient of gradually accumulating changes and has a direct impact on the hydrochemical and hydrobiological regime below the Angara riverbed.

Abstract: Aim We investigated the hypothesis that flood decreases the taxonomic and functional beta diversity of Chironomidae (Diptera) larvae among floodplain lakes, causing biotic homogenization. Methods We collected benthic samples using a modified Petersen grab in 18 lakes in a flood period (March 2011) and a drought period (September 2011) in the Upper Paraná River floodplain. We compared the taxonomic and functional beta diversity of Chironomidae among lakes in flood and drought periods using a multivariate dispersion analysis (PERMDISP). Results We found similar taxonomic and functional beta diversity of the Chironomidae between hydrological periods. Conclusions We did not find evidence of biotic homogenization due to flood pulse. Our findings suggest other mechanisms besides increasing connectivity and environmental similarity due to flood pulse that may structure the benthic community, such as variation in the identity of flood-tolerant morphospecies across lakes.

To compare trophic characteristics for pelagic and bottom communities of zooplankton and zoobenthos in the western Chukchi Sea, isotopic composition of carbon and nitrogen (δ13С and δ15N) is determined for three different types of water masses. The main area of the southwestern part of the sea (to the south of 71оN) is occupied by the surface and subsurface water masses invaded from the Bering Sea with relatively high δ13C and low δ15N values. The cold Arctic waters prevail in the northwestern area. The western periphery of the sea is influenced by the water masses from the East Siberian Sea transported by the alongshore Siberian Current, distinguished by significantly lowered δ13С values and somewhat (by 1–3 ‰) increased δ15N values. A stable difference in the carbon isotopic composition between zooplankton and benthic invertebrates is revealed in the southwestern Chukchi Sea that means that the benthic organisms are based mainly on the bottom food chain, with a minimal input of organic matter from the water column. In the area influenced by the water masses from the East Siberian Sea, benthic invertebrates have the lowest values of δ13С comparable to those of zooplankton that is a sign of organic sediments from the water column utilization, partly terrigenous in origin. The role of primary producers for plankton and benthos in the northwestern Chukchi Sea has not been fully elucidated and requires additional studies. However, the main trophic base for the benthic community is assumed there to be organic matter removed from the water column, originated mainly from ice algae.

Environmental engineering survey performed at the construction site of the Amur Gas Chemical Complex in 2018 in order to assess the state of aquatic communities of the Zeya River revealed 37 taxa of planktonic algae (below genus rank), 32 species of zooplankton, and 37 species of benthic organisms. In May, phytoplankton was mainly represented by diatoms; in July, it was more diverse, when green algae, golden algae and cyanobacteria all played a significant role. In May, zooplankton included mainly rotifers; in July, crustaceans dominated by biomass at most stations. Zoobenthos was represented in May mainly by oligochaetes and bivalves, while insects dominated in July. The abundance and biomass of phytoplankton, zooplankton, and benthos were low. The Goodnight–Whitley, Parele, Woodiwiss, and Mayer indices testified to relatively favorable environmental conditions in the studied sections of the Zeya River. According to the indicators of phyto- and zooplankton, and zoobenthos, the waters of the river are classified as oligosaprobic.

Feeding features of juvenile muksun Coregonus muksun (Pallas, 1814) when growing in cages installed on the channel of the Lower Ob are considered. It was found that, along with artificial food, juveniles feed on zoobenthos and zooplankton organisms that enter cages during drifting, and consumption was noted from the first to the last days of rearing. The bulk of the food bolus was artificial food, 88.3–94.3%; aquatic invertebrates accounted for 1.3–5.7% of the weight of the food bolus where Chironomid larvae dominated. There were no statistically significant differences in the intake of invertebrates by young muksun before and after feeding (p = 0.442) at average values of 0.005 and 0.006 g, respectively. The ability of the transition of juveniles from artificial to natural food base at all stages of development was noted, which is an indicator of successful adaptation to environmental conditions during cage rearing in the channels of the Ob River. [ABSTRACT FROM AUTHOR]

Bivalve mollusks are an important component of the ecosystems of many natural and artificial reservoirs. However, the ecological role of some of them is very ambiguous, especially if we talk about invasive species that have spread widely beyond their natural habitats over the past 100 years. The present study aims to obtain quantitative estimates of the distribution of a southern invasive species, the zebra mussel bivalve mollusk, over the water area of the Ivankovo reservoir and to assess the contribution of its filtration capacity to water self-purification. [ABSTRACT FROM AUTHOR]

Hydrobiological research of the main components of the biota of the lower reaches of the Sula River was conducted. The river flows into the Kremenchutsk Reservoir. Zoobenthos, zooperiphyton, vascular water plants, and ichthyofauna in lotic and lentic microbiotopes were studied. Species and communities of protected status were stated. It was shown, that a significant share (about 30%) consists of rheophilic species. 28 species of fish were registered in the studied area, of which eight are invasive species and 10 are under protection. The biotopic distribution of different fish species, and the intensity of the downstream migration of juvenile fishes in spatial, temporal, and species aspects were estimated. It was identified, that about 12 million young fish migrate from the researched part of the Sula River to the Kremenchuk reservoir during the season. [ABSTRACT FROM AUTHOR]

Over the past fifteen years, the frequency of occurrence of the alien mollusk Anadara kagoshimensis (Tokunaga, 1906) increased from 5 to 17–23% in the zoobenthos of the southern coast of the Crimean shelf. At the same time, the proportion of the alien mollusk was not significant and varied from 0.73 to 23.29% of the biomass and from 0.19 to 2.20% of the abundance of the macrozoobenthos in the benthic communities. The mollusk A. kagoshimensis was recorded in three communities: Chamelea gallina,Gouldia minima–Pitar rudis, and Gouldia minima. The mollusk Anadara has not formed an independent community there. The effect of this alien species on the benthic communities of the Crimean shelf was not as significant as on the bottom communities in the northwestern or in eastern parts of the Black Sea shelf. The structure of benthic communities has not significantly changed on the shelf of the southern coast of Crimea when compared to the 1970–1980s. The first record and the introduction of the alien mollusk to the Crimean shelf coincides with a decrease in salinity and an increase in temperature of the coastal waters that have been observed in the last decade. [ABSTRACT FROM AUTHOR]

Globally, lakes are warming and browning with ongoing climate change. These changes significantly impact a lake's biogeochemical properties and all organisms, including invertebrate consumers. The effects of these changes are essential to understand, especially during critical periods after and before the growing season, that is, autumn and spring, which can determine the composition of the invertebrate consumer community.In this study, we used a large‐scale experimental pond system to test the combined effect of warming (+3°C) and increased input of terrestrial and coloured dissolved organic carbon (gradient of 1.6–8.8 mg/L in the ambient and 1.6–9.3 mg/L in the warm)—which causes browning—on zooplankton and benthic macroinvertebrate biomass and composition during the autumn and the following spring.Total zooplankton biomass decreased with warming and increased with browning, while total zoobenthos did not respond to either treatment. Warming and browning throughout the autumn had no overall interactive effects on zooplankton or zoobenthos. Autumnal warming decreased total pelagic consumer biomass, caused by a decrease in both Rotifera and Copepoda. In contrast, there was no effect on overall benthic consumer biomass, with only Asellus sp. biomass showing a negative response to warming. An autumnal increase in dissolved organic carbon led to increased total pelagic consumer biomass, which was related to increases in Daphnia sp. biomass but did not affect zoobenthos biomass. While we expected zooplankton and zoobenthos biomass to follow responses in primary and bacterial production to treatments, we did not find any relationship between consumer groups and these estimates of resource production.Our results suggest that consumer responses to warming and browning during autumn may lead to less overarching general changes in consumer biomass, and responses are mostly taxon‐specific.This study gives novel insights into the effects of warming and browning on consumer biomass during autumn and spring and increases the understanding of the effects of climate change on invertebrate community biomass in the different habitats. [ABSTRACT FROM AUTHOR]

This article presents a study of the technology of growing carp (Cyprinus carpio) using different stocking densities in feeding ponds. Carp is one of the most common and essential freshwater fish species for commercial farming and consumption. The study was conducted over several months, with an assessment of carp's growth, survival, and productivity when using different stocking densities in feeding ponds. Different stocking densities included low (sparse), medium, and high (dense) carp individuals per unit area. To experiment, four groups of carp individuals were kept in feeding ponds at different stocking densities from 2,000 to 3,500 specimens per hectare of water area. Using extensive planting material of carp with an average weight of 55 g makes it possible to obtain commercial carp with an average weight of 485 g to 650 g during a two-year cycle of cultivation in the conditions of the second fish farming zone without reducing fish production. At the same time, the largest concentration of carp was obtained in a pond with sparse planting of annuals – 2.0 thousand specimens/ha. An increase in the planting density of yearlings of carp to 3.5 thousand units/ha led to a decrease in the average daily weight of two-year-old carp to 510 g while maintaining a high fish production of 1122 kg/ha. At the same time, a hydrochemical analysis was carried out in the ponds, and the amount and biomass of the natural feed base (phyto-, zooplankton, and zoobenthos) were determined. The analysis of the research results indicates that the stocking density of carp has a significant impact on its productivity. The sparse stocking conditions promoted more significant growth and better development of the fish, which may be due to less competition for food and space. On the other hand, high stocking density led to a slight decrease in growth and did not affect survival and fish productivity. The results of this study have practical applications for fish farms engaged in the cultivation of carp. They emphasize the importance of an optimal balance between the number of fish, the availability of natural feed, and the area of the feeding ponds in order to achieve maximum growth and productivity with minimum costs of keeping and feeding the fish. Such research will help improve fish farming technologies and optimize production processes to ensure sustainable and efficient development of the industry. [ABSTRACT FROM AUTHOR]

In August 2021, two specimens of alien oligochaetes of tropical origin Branchiura sowerbyi were found in the Sheksna Reservoir of the Vologda oblast (59°45′21″ N, 38°21′28″ E). As of today, this is the northernmost finding of this species. Probably, this species penetrated with the ballast waters from the Don River lower course through the Volga-Don canal and the Volga-Baltic waterway. The temperature regime of the water bodies of the Vologda region allows reproduction of this oligochaete. [ABSTRACT FROM AUTHOR]

In Sevastopol Bay, a decrease in the number of species and the disappearance of some zoobenthos communities was recorded back in the 1920–1930s and persisted until the 1960–1990s. Only five species of macrozoobenthos were the most resistant to high anthropogenic load and eutrophication in those years. The relative recovery of the species composition and the improvement of benthic biological parameters have been observed in the bay since the beginning of the 21st century. The zoobenthos was replenished by 39 new species which here were not marked earlier. The largest number of species was recorded for Mollusca, Crustacea, and Polychaete. These changes occurred even in those areas of the bay where previously benthic animals were absent in zoobenthos samples or found in very small numbers, conditionally a dead zone. The reduction in the eutrophic level, the improvement in the oxygen regime, and the expansion of the area with oxidizing conditions in the bottom sediment were the major factors in the improving benthic habitats in Sevastopol Bay. These ecological changes coincided with increase in the water temperature in the summer period. Positive zoobenthos tendencies are typical for Romanian and Bulgarian coasts in the last decade. [ABSTRACT FROM AUTHOR]

Gut microbiota is closely related to the health of the host and its adaptation to environmental changes. Sinopotamon planum is a species of freshwater crab that lives in the water for three seasons and plays a key role in freshwater ecosystems as a benthic macroinvertebrate, an important indicator of aquatic ecological health. In this study, we sequenced 60 gut microbial samples of S. planum and nine microbial samples from the surrounding water in spring, summer, and autumn based on the 16S rRNA gene. The results showed that gut microbiota had the highest alpha diversity in summer, which may be related to increased adaptability in summer. Firmicutes, Proteobacteria, and Bacteroidota were the most dominant phyla of gut microbiota across three seasons, with Candidatus Hepatoplasma and Candidatus Bacilloplasma being the main genera. These main phyla and genera may be key to maintaining a stable function of the intestinal environment. Firmicutes was the phylum with the highest relative abundance, which is probably related to the carnivorous behaviour of S. planum. The abundant C. Hepatoplasma may be related to the starvation of S. planum in the wild. In both gut and water microbiota, beta diversity analyses showed significant differences across seasons. Comparative analysis of gut microbes and surrounding water microbes showed significant differences in microbial diversity and composition between gut and surrounding water. In conclusion, the structure of the gut microbial community of S. planum differed significantly between the studied seasons, but the water microbial community around S. planum was less variable and significantly different from the gut microbes. The seasonal differences in gut microbes are more likely the result of self-internal adaptation to changes in water temperature and food resources between seasons. [ABSTRACT FROM AUTHOR]

Global climate change might result in permafrost thaw and the formation of thermokarst landscapes that release long-term carbon stocks as greenhouse into the atmosphere, thereby initiating a positive climate feedback. These processes are mediated by biological activity, including by microbes, vascular plants and animals, whereas the role of invertebrates in thermokarst ecosystems remains poorly understood. We investigated the diversity and assemblage structures of zooplankton (mainly Copepoda, Cladocera), microbenthos (testate amoebae) and meio- (Copepoda and Cladocera) and macrozoobenthos (mollusks, crustaceans, insects and annelids) from a range of water bodies representing different stages of thermokarst lake formation in the southern part of the Lena River Delta (Central Siberia). Altogether, 206 species of testate amoeba, mollusk, crustacean, insect and annelid taxa were identified. A total of 60 species of macrozoobenthos (mainly insects) and 62 species of testate amoebae were detected in the water bodies of the Lena River Delta for the first time. The species richness of zooplankton and meio- and macrozoobenthos was greater in the large thermokarst lakes than in the polygonal ponds due to the freezing of the latter in the winter. In contrast, the species richness of protists was higher in the polygonal ponds, which was related to the habitat preferences of testate amoebae. Fish grazing strongly affected the macrobenthos assemblages but not the smaller-sized organisms. Water acidity and temperature were the main environmental drivers of the assemblage structure of testate amoeba and microcrustacean. The species structure of the macroinvertebrate assemblages was significantly explained by water acidity, permafrost depth and size of the water area. It means that small size organisms with their short generation times are sensitive to more dynamic factors such as temperature and may serve as indicators of ecosystem changes due to global climate warming. In contrast, large size organisms are affected by driven factors that appear during thermokarst lakes formation and permafrost degradation. [ABSTRACT FROM AUTHOR]

The current state of zoobenthic communities has been studied for lakes Sukkozero and Gimolskoe in the western part of the Republic of Karelia (Muezersky district). Under conditions of highly colored and low mineralized waters, chironomid larvae, caddisflies, mayflies, and oligochaetes predominate in the communities. Biomass and abundance ranged within 0.41–0.75 g/m2 and 315–685 ind./m2 in Lake Sukkozero and 0.41–0.93 g/m2 and 220–346 ind./m2 in Lake Gimolskoe in 2017–2018. The highest abundance and biomass were noted in the biotopes of silty sediments (overgrown littoral and profundal); the lowest were at the sandy littoral. According to the quantitative parameters of zoobenthos, Lake Sukkozero was an oligotrophic water body; Lake Gimolskoe was mesotrophic. Using common biotic indices to assess the ecological quality of waters (indices Mayer's, oligochaete, chironomid, and saprobity), it was revealed that low mineralization and high humus content might affect their performance and distort the assessment of real organic pollution. [ABSTRACT FROM AUTHOR]

In 2010–2013, the benthic fauna was studied in the Novinkinskoe, Belousovskoe, and Vytegorskoe reservoirs for the first time. In zoobenthos, 103 species and taxa of a higher rank were identified. An increase in quantitative indicators, species richness, and diversity were noted in the series profundal → open littoral → thickets. The profundal of all reservoirs was characterized by the Limnodrilus hoffmeisteri–Procladius complex. In the littoral, the structure of communities was predetermined by the type of substrate and the type of thickets. The highest quantitative indicators of zoobenthos were recorded in the abnormally hot year of 2010. Compared to the Volga River reservoirs located to the south, the zoobenthos of the Novinkinskoe, Belousovskoe, and Vytegorskoe reservoirs was characterized by lower quantitative indicators and species richness. [ABSTRACT FROM AUTHOR]

The results of long-term studies are used to present, for the first time, the structural organization of zoobenthos communities and the dynamics of their density and biomass in rivers and brooks of the the Khektsir Ridge, including the boundaries of the Bol'shekhekhtsirskii Reserve, Khektsirskii Wildlife Reserve (the southern part of the Russian Far East). The benthic organisms were found to contain 23 groups (22 groups in the spring and summer, 19 groups in the autumn, and 8 groups in the winter). Leading in the occurrence frequency (>90%) were chironomids, mayflies, and oligochaetes. The chironomids and amphipods accounted for 37.0 and 19.1% of the total benthos density, and mollusks and amphipods, for 32.1 and 29.7% of the total biomass, respectively. Dominants in terms of density and biomass were amphipods; chironomids dominated in terms of density, and mollusks, in terms of biomass. The mean density of benthic organisms was 637 ± 21 spec./m2, and the mean biomass was 1.8 ± 0.2 g/m2. The benthic communities of rift segments in the rithral zone were found to be most productive. It is shown that the seasonal and long-term dynamics of zoobenthos communities is pronounced and can be traced in the group composition, structure, and quantitative characteristics. [ABSTRACT FROM AUTHOR]

Lake vegetation is divided into 3 ecological groups: hygrophytes, hydrophytes and hydratophytes. Hygrophytes make up 27.2%, hydrophytes-9.0% and hydrophytes-63.6%. Hygrophytes are plants that grow in moist places, on the shores, and hydrophytes are half aquatic. This plant species is found in small numbers in the lake. Hydrotophytes are dominant in abundance and biomass. The area of the lake is 7,200 hectares, of which the water part is 3,800 hectares, the area of wetlands covered by various parts is 3,400 hectares. The lake is rich in organic nutrients. A wide variety of higher algae grows in the lake (Phragmites communis, typha angustifolia, Potamogeton crispus, Myriophyllum spicatum, Ceratophyllum demersum, Chara infarmedia, Spirogyra, as well as many species of algae), which prevents sunlight from penetrating into the water to a depth of 3 meters, which negatively affects the development of zooplankton.

Multiple stressors, including climate change, eutrophication, and pesticide contamination, are significant drivers of the decline in lake zoobenthos. Zoobenthos play a crucial role in aquatic ecosystems, impacting energy dynamics, nutrient cycling, and sediment degradation. However, these stressors have led to a decrease in the abundance and diversity of zoobenthos, resulting in notable changes in species composition and structure. Eutrophication typically increases zoobenthos abundance while reducing taxonomic diversity. Climate change, such as warming and heatwaves, also affects the zoobenthos community structure, with different species exhibiting varying levels of adaptability to temperature changes. Additionally, pesticides like imidacloprid have negative effects on the survival and growth of zoobenthos. However, the interactions between imidacloprid and other stressors remain understudied. Here, we used 48 mesocosms (2500 L) to simulate shallow lakes. We combined nutrient loading, sustained warming, and the imidacloprid pesticide to test how these stressors interactively influence the survival and community of zoobenthos. The experimental results demonstrate that elevated temperatures have a significant impact on aquatic benthic organisms under different treatment conditions. The increase in temperature led to a notable rise in species richness and α-diversity, primarily attributed to the stimulation of metabolic activities in zoobenthos, promoting their growth and reproduction. This finding underscores the potential influence of climate change on aquatic benthic ecosystems, particularly in terms of its promoting effect on α-diversity. However, it is essential to note that elevated temperatures also reduced β-diversity among different sites, implying a potential trend toward homogenization in zoobenthos communities under warmer conditions. Moreover, this study revealed the interactive effects of multiple stressors on the diversity of aquatic benthic communities. Specifically, the pesticide imidacloprid’s impact on zoobenthos is not isolated but demonstrates complex effects within various treatment interactions. In the presence of both temperature elevation and the addition of imidacloprid, the presence of imidacloprid appears to counteract the adverse effects of temperature elevation, resulting in increased species diversity. However, when imidacloprid coincides with nutrient input, it significantly affects α-diversity negatively. These findings highlight the complexity of zoobenthos responses to multiple stressors and how these factors influence both α-diversity and β-diversity. They provide valuable insights for further research on the conservation and management of ecosystems.

The presence of the invasive amphipod Gmelinoides fasciatus (Stebbing, 1899) has been established for the first time in the watercourse of the basin of Lake Vodlozero (Novguda River, a tributary of the Ileksa River), which is located on the territory of the Vodlozersky National Park (northwestern Russia). The new habitat is at a considerable distance from the previously known ones. The shortest route through water bodies (Ileksa River–Vodlozero Lake–Sukhaya Vodla River–Vodla River–Onega Lake) is about 180 km. This raises questions about the path and mode of spread of the invasive species. Along with migration through water bodies, it is proposed to consider the version of introduction of amphipods by tourists, in particular fishermen, with equipment or bait. A detailed survey of the littoral zone of Lake Vodlozero is recommended to determine the extent of the invasive settlement. [ABSTRACT FROM AUTHOR]

The role of reeds in the functioning of ecosystems and their significance for zoobenthos in the coastal lagoons is poorly understood. We hypothesise that next to the spatial zonal differentiation of abiotic factors in the apparently homogeneous habitat of reeds, benthic macroinvertebrate fauna is also unevenly distributed, and differs in taxonomic and functional diversity, as well as density and biomass across the reed stand. The research was carried out in the Vistula Lagoon (southern Baltic) along three designated sectors arranged parallel to the shoreline and differing in distance from the shore and depth. Mean density of reed stems in the analysed stand was within the range of values reported from different American and European wetlands. Regardless of the location within the reeds and the season, the fauna was dominated by detritivorous Tubificinae and larvae of Chironomidae. The highest diversity, density, and biomass of fauna were found in the middle littoral zone, and the lowest in the outer zone adjacent to the open water. The presented data support our hypothesis predicting the existence of a spatial variation pattern in the composition and distribution of macroinvertebrates in response to the changing zonal habitat conditions within the reed stand.