Bottom Invertebrates Research Articles

Zoogeographical composition of macroinvertebrates in low-mountain lakes of the Russian Altai

In 2022 the taxonomic and zoogeographic composition of the macrozoobenthos of six lowland lakes of the Russian Altai: Aya, Beloe, Kireevo, Kolyvanskoe, Koksha and Svetloye was investigated. In the studied lakes 156 species of zoobenthos from 9 classes of invertebrates were identified. The largest number of species is characteristic of the insect class. Chironomids and oligochaetes dominated in terms of frequency of occurrence in the lakes. Of the oligochaetes, the family Tubificidae (68%) was more frequently observed. Tubificidae (68%), chironomids — subfamilies Chironominae (91%) and Tanypodinae (66%). The maximum species diversity of zoobenthos was observed in lakes Beloe (81 species) and Koksha (76 species), the least number of species was found in lakes Aya (41 species) and Kireevo (52 species). Lakes Beloe — Kireevo — Kolyvanskoe and Koksha — Svetloye are the most similar in composition of benthic invertebrates. The most original was the taxonomic composition of the deepest lake Aya. According to the taxonomic composition of the fauna of bottom invertebrates, most lakes (Aya, Beloe, Kireevo, Kolyvanskoe) were closer to plain water bodies, two lakes (Koksha, Svetloe) combined features of both plain and mountain lakes. Zoogeographic analysis of the fauna of benthic invertebrates of foothill lakes revealed 12 types of distribution. Holarctic (39%), Palaearctic (23%) and Western Palaearctic species (21%) were predominant in the lake fauna. Comparative analysis of the fauna of the identified homotopic and heterotopic species showed that the most extensive areas are found only among homotopic primary aquatic archaic taxa. Zoogeographic analysis of the studied lakes indicate their proximity to the border of the Western and Eastern Palearctic.

Current state of zooplankton and zoobenthos in the lower stream of the Chulym river (Obi river basin)

A comparison was made of the numerical indicators of zooplankton and zoobenthos of the Chulym River in comparison with those obtained in 1972–1973 in order to assess the transformation of the ecosystem that has occurred over 50 years. It is shown that the zooplankton of the Chulym River has undergone dramatic changes, both qualitatively and quantitatively. The number of zooplankton increased 4–5 times due to small rotifers. At the same time, the zooplankton biomass, and therefore the feed value, decreased by more than half due to a reduction in the number of large crustaceans. The species composition of structure-forming zooplankton species has changed. The number of rotifer species in the riverbed decreased from 55 rotifers to 34. The species of Trichocerca family dropped out of the dominant composition and representatives of the river began to dominate Brachionus family. There is a significant change in the structure of zoobenthos: the number of organisms in the Chulym River bed is 5 times lower than in the 1970s. The species composition in benthic communities has remained almost unchanged over 50 years, while the proportion of some heterotopic insects (caddis flies, mayflies, stoneflies) has increased, and the proportion of oligochaetes, mollusks and chironomids in the biomass has decreased by 4–5 times. In the accessory reservoirs of Chulym, the abundance and biomass of zooplankton and zoobenthos over the past 50 years have remained more or less stable, which may indicate the presence of chronic pollution that affects the ecosystem of the main river channel and does not have time to have a negative impact on the accessory reservoirs during floods. The water quality indicators of the Chulym River and its subsidiary reservoirs, according to biotic indices, are low and correspond to a low or poor water quality class. Such conditions are unfavorable for the further development of zoobenthos and, accordingly, ichthyofauna, for which bottom invertebrates are the food supply.

Macrozoobentos on the shelf of the Kronotsky Gulf

Data about the taxonomic composition and spatial distribution of bottom invertebrates of Kronotsky Gulf were obtained on results of bottom grab survey carried in September 2002. Analysis of the samples revealed 72 species of Polychaeta, 21 species of molluscs (Bivalvia), 17 species of crustaceans (mostly Amphipoda), 2 species of echinodermata (Echinoidea and Ophiuroidea). The average biomass in the depth range 25–200 m was 242±116 g/m2 where average density was 306±51 organisms/m2. The most high values of biomass were observed in the outlet parts of the rivers Zhupanova, Semyachik, Kronotskaya, where contribution of sea dollar Echinarachnius parma communities was principal. Despite fluctuations of the biomass of particular taxons during 50 years, the total biomass keeps stable (206–242 g/m2). Like in 1949 E. parma plays the main role in most bottom communities.

Assessment of the ecological state of small rivers of St. Petersburg according to the benthic macroinvertebrates indicators in 2019-2021

The work is devoted to the topical issue of assessing the state and changes of river ecosystems located within the boundaries of large cities and industrial agglomerations. The paper presents the results obtained during hydrobiological studies on small rivers of St. Petersburg (Russian Federation) in 2019-2021. The application of bioindication methods is substantiated in order to assess long-term changes in aquatic ecosystems under conditions of increasing anthropogenic load. Various characteristics of the community of benthic invertebrates are used as biological indicators of the state of hydroecosystems. Benthos samples were taken on eight small watercourses of the city, which are both tributaries of the Neva River of various orders (the Okhta, Slavyanka, Chernaya Rechka, Lubya, Okkervil, Volkovka rivers) and delta watercourses (the Smolenka and Karpovka rivers). The paper provides a brief description of the studied water bodies and sampling sites. A number of biotic metrics and biotic indices used for bioindication purposes both in Russia and abroad have been identified. It is noted that the unstable hydrochemical regime and low flow velocity in the small watercourses of the Neva River delta contribute to the intensification of the accumulation of sediments with high concentrations of ecotoxicants, which negatively affects both quantitative and qualitative characteristics of biocenoses. In some watercourses re is a complete absence of bottom invertebrates, which can be assessed as an ecological disaster. When assessing water quality by quantitative and qualitative characteristics of communities of benthic invertebrates (Mayer index, BMWP index, some biotic metrics), it can be concluded that Okkervil River, Chernaya Rechka River and Volkovka River should be attributed to watercourses whose ecological state is extremely unfavorable. The ecological state of the rivers Karpovka River, Slavyanka River, as well as the estuaries of Okhta River and Smolenka River should be considered unfavorable. And finally, the situation in Lubya River, the source of Smolenka River and in the middle reaches of the Okhta River can be considered close to satisfactory (low quality according to BMWP or moderately polluted water according to IM).

Responses of bottom invertebrates to pollution in the Arctic: bioassays with blue mussel Mylilus edulis L.

Environmental control in the Arctic ecosystems needs to be changed to hi-tech monitoring technologies with IT systems for actual and ecologically effective 'arctic safeguard'. In circumstances of the fragile arctic ecosystems, priority bioassay of possible toxic hazards in natural seawater must be undertaken. It was considered useful to examine toxic responses of some indicator species. Bivalves are well-known indicators of pollution stress arising from the activities of man, such as off-shore drilling and oil transportation, dredging or the release of pollutants. Toxic effects of some drilling fluids on energy balance, behavior and survival of the common mussel Mytilus edulis L, were estimated in long-duration bioassays of about 30 days each. The highest sensitivity of behavioral responses to any changes in chemical water composition was found. Mussels of the Barents Sea had significant differences from the control by four behavioral parameters even at 0.01 g/l of the ferrochrome-lignosulfonate drilling fluid, while the significant differences from the control in oxygen consumption and filtration rates were observed only at the 10 g/l. Even small concentration of another standard water-based drilling fluid with barite (of about 0.05 g/l) had a lethal effect on M. edulis.

Discharge of drill cuttings in the Arctic seas and responses of bottom fauna: bivalve Mytilus edulis L.

Drill cuttings are the largest solid waste of drilling operations. Onsite discharge of drill cuttings into the marine environment is relevant and can be permitted under certain conditions and regulations. Environmental impact of the on-site discharge of drill cuttings is poorly understood for the Arctic shelf. A risk assessment of the discharge is required and the related biological effects are estimated in bioassays on various local species. The sublethal screening tests of water-soluble fraction of drill cutting (WSF DC) were performed on a test-organism of the Barents Sea coast, blue mussel, Mytilus edulis. Physiological (oxygen consumption and filtration rates) and behavioral (shell gaping) activity of mussels was affected by the tested WSF DC above the certain threshold concentration. In general, biological effects of WSF DC might be assumed as a toxic stress of low intensity. Behavioral responses are the most sensitive in blue mussels and behavior of this sentinel organism is to be applied as a reliable indicator of environmental stress. Environmental impact from the drill cuttings of water based drilling fluid appears to be less toxic-stressful for M. edulis and many other bottom invertebrates than it might be expected from release of some drilling fluids.

The state of hydrobionts in the Tyub‐Karagan Bay structure, Kazakhstan

Aim. The purpose of the research was to study the state of hydrobionts in the Tyub‐Karagan Bay structure by season for a comparative analysis of their state with previous studies by the authors.Material and Methods. The conditions of hydrobionts (phyto, zoo‐plankton and macrozoobenthos) of the Tyub‐Karagan Bay structure have been studied for three seasons. Studies were carried out by traditional methodology.Results. The species composition of phytoplankton communities in spring was found to be less constant than in autumn; this is associated with heterogeneity in external conditions at the beginning of the growing season. The seasonal dynamics of zooplankton conformed to certain patterns. As a rule, from the beginning to the end of the growing season there was an enrichment of species composition and an increase in the quantitative indicators of zooplankton communities. The highest biomass was formed by bottom cenoses, where large mollusks play a leading role.Conclusion. During the 2018 research period, species richness and species diversity of phytoplankton were at a high level. Representatives of two categories were observed most often. Blue‐green dominated in number, while diatoms formed the basis of biomass. Species richness and species diversity of zooplankton was at a low or moderate level and most often constant. The seasonal dynamics of macrozoobenthos had common and specific features, depending on the research station location. Disproportionate changes in the quantitative indicators of bentonites are associated with a decrease in the average weight of individuals by autumn. This happened both through the strengthening of the role of small species and by an increase in the proportion of younger age stages in populations of bottom invertebrates.

Зообентос лососевых рек национального парка «Анюйский» (Хабаровский край, Россия)

The fauna of bottom invertebrates in watercourses of the Anyuysky National Park belongs to the rhytron type and is characterised by a large variety of its composition (20 groups in total), of which amphibiotic insects of the lithoreophilous complex make up 80% of the total benthos density and 75% of its total biomass. This is typical of salmon rivers in the south of the Russian Far East. The second largest group is amphipods which play an important role in aquatic ecosystems in the processing of leaf litter and dead bodies of salmon fishes after their spawning. The density of benthic organisms in the watercourses of the Anyuy River basin and Gassi Lake varied from 5 to 18 256 ind./m2, biomass from ˂0.1 to 32.0 g/m2 (on average 622 ± 52 ind./m2 and 1.2 ± 0.1 g/m2). Mayflies and chironomids dominated in density, while amphipods, stoneflies, and caddisflies dominated in biomass. The occurrence of organisms was as follows: chironomids and mayflies (100% each), caddis flies (99%), stoneflies (88%), amphipods and oligochaetes (87% each), other Diptera (82%). Sialidae, Hirudinea, Asellidae, and Hymenoptera (Ichneumonidae) were rare (<10 %). Interesting and rare finds include chironomids Kaluginia lebeteformis lebetiformis Makarchenko and beetles from the family Psephenidae Lacordaire, which live only in rivers with clean and transparent water, fast currents, high oxygen concentrations, low water temperatures, gravel-pebble and stony soils. According to the state of benthic communities, the water quality of the foothill and mountain rivers and streams in the protected area was assessed in the range from class 1 to 3. Changes in the structural characteristics of the zoobenthos in the Bira channel of the Anyuy River caused by anthropogenic impact were revealed.

Hydrobiological characteristics of the Don River in the region of the Bagayevsky hydroelectric complex construction

The data on the taxonomic composition and quantitative characteristics of planktonic and benthic communities of the Lower Don in the area of construction of the Bagaevsky hydroelectric complex have been presented. In June - July 2018, a comprehensive hydrobiological survey was carried out to assess the taxonomic composition and quantitative characteristics of phytoplankton, zooplankton and zoobenthos. Hydrobiological samples were taken at 21 stations using standard techniques. The phytoplankton communities contained 110 taxa, zooplankton - 58, zoobenthos - 78. The spatial distribution of quantitative indicators of plankton and benthos in the investigated area has been presented. Phytoplankton abundance varied from 2,006.0 to 6,128.0 million cells/m, biomass - from 1.00 to 7.37 g/m, the average polygon indicators were 3,636.6 ± 223.5 million cells/m and 4.28 ± 0.39 g/m respectively. In terms of the number of registered taxa and quantitative indicators, two groups of phytoplankton dominated - cyanobacteria and green algae. The abundance of zooplankton ranged from 2,580 to 238,622 ind./m, biomass ranged from 36.4 to 476.0 mg/m, the average abundance was 74,690 ± 15,017 ind./m and 172.7 ± 24.8 mg/m respectively. Rotifers and cladocerans were the leaders in the number of species. Meroplankton was dominant in numbers (mainly due to mollusk larvae), and copepods were the dominant group in biomass. The number of bottom invertebrates varied from 20 to 17,867 ind./m, biomass from 0.02 to 2,114.0 g/m, the average zoobenthos abundance was 3,462 ± 898 ind./m, biomass 133.9 ± 102.0 g/m respectively. The maximum number of taxa was recorded among crustaceans and chironomid larvae. The basis of abundance was formed by oligochaetes and insect larvae, mainly chironomids, mollusks dominated by biomass. The resulting materials can be used as background materials in assessing the impact of construction on the hydrobiological communities of the Lower Don.

Отношение организмов семейства Gammaridae к содержанию кислорода в придонном слое воды в Северном Каспии

The research of bottom invertebrates Gammaridae was carried out in 2013-2017 in the western part of the North Caspian. The purpose of the study was to determine the environmental tolerance of the organisms to oxygen. Oxygen deficit was caused by temperature and salinity stratification of water masses.Hypoxia was formed mainly in some areas of the shallow zone (up to 5 m) on the border of the Northern Caspian – Middle Caspian, as well as in areas with fine-grained sediments.Representatives of Gammaridae are characterized by high frequency of occur-rence.During the research period the number and biomass of the studied organisms widely varied. Gammarus Fabricius dominated by the total number, Dakerogammarus Stebbing – by the total biomass.The maximum frequency of occurrence was characteristic for Niphargoides similis (G. O. Sars).The limits of tolerance to oxygen of individual Gammaridae species living in the Northern Caspian sea have been presented.The minimum concentration of oxygen recorded for the entire period of research (1.29ml/l; 21%) is not critical for one species – Niphargoides similis (G. O. Sars). The low concentration (3 ml/l) does not inhibit the development of Niphargoides macrurus (Sars), Gammarus ischnus Stebbing, Gammarus pauxillus Grimm and Dikerogammarus haemobaphes (Eichwald). Other Gammaridae representatives living in the western part of the Northern Caspian were found in the environment with absolute oxygen concentration over 3.63 ml/l and with relative oxygen concentration over 59%.Wide ecological valency for oxygen is typical for Niphargoides similis (G. O. Sars), Gammarus pauxillus Grimm, Dikerogammarus haemobaphes (Eichwald), Gammarus ischnus Stebbing, and Niphargoides macrurus (Sars).

Экологическая валентность к кислороду северокаспийских мизид и кумовых ракообразных

The paper focuses on the problems of violation of the ecological balance, changes in the nutrient load, undermining the ecosystem’s biopotential, caused by anthropological pressure and resulting in deterioration of the oxygen regime in the bottom layer of water. The purpose of the research was to determine the environmental oxygen tolerance in bottom invertebrates, representatives of the orders Mysidacea and Cumacea, which are forage objects for beluga, sturgeon, stellate sturgeon, bream and pike perch. The research was conducted in 2013-2017 in the western part of the North Caspian. Developing of oxygen deficiency in the studied water area was due to thermohaline stratification of water masses. Hypoxia was formed in local areas. Representatives of Mysidacea predominantly inhabiting the bottom layers have a low frequency of occurrence, because they live in a narrow range of oxygen content (about 5-7 mg/l). A low oxygen concentration (less than 3.95 ml/l (74%)) inhibits the development of Mysidacea. Paramysis ullskyi prevailed in the total number of samples taken from macrozoobenthos, and Paramysis lacustris prevailed in the total biomass. Limnomysis benedeni and Paramysis ullskyi were the most resistant to oxygen deficiency. These species have a maximum ecological valence to oxygen. Representatives of the order Cumacea are characterized by a high frequency of occurrence. The species Schizorhynchus bilamellatus dominated in the surveyed water area, both in abundance and biomass. Cumacea live in a wide variability of oxygen content. Schizorhynchus bilamellatus and Stenocuma graciloides are most resistant to oxygen deficiency. These species have a maximum ecological valence to oxygen. The minimum oxygen recorded over the entire research period (1.29 ml/l; 21%) is not critical for Stenocuma graciloides. The results of the study are of practical value for assessing the condition of the food supply of benthos-eating fish that are commercialized in the western part of the North Caspian

Taxonomic composition and trophic structure of benthic fauna in rocky rapids and riffles in rivers of the Republic of Karelia and Murmansk Oblast

The composition of bottom invertebrates in rocky rapids and riffles in rivers of the White, Barents, and Baltic seas in the territory of Eastern Fennoscandia is presented and analyzed. A total of 114 species (137 taxa of different ranks) have been identified. Most of them have Euro-Siberian (44%) and Palaearctic (36%) distribution. Regarding the feeding mode, collector–gatherers (32%) and collector–filterers (25%) dominate among trophic groups. Differences in the composition of zoobenthos between the southern and northern parts of the region can be explained not by the fauna genesis, but by latitudinal zoning.

USE OF MACROINVERTEBRATES FOR ASSESSMENT OF RESTORATION WORKS INFLUENCE ON THE HABITAT IN FLOODPLAIN LAKES

The paper presents a study concerning the influence of the hydraulic and hydrological connectivity among the oxbow lakes and the restoration of riparian-zones have on aging. Interconnectivity oxbow lakes emerge after complex regulating works for the protection of the shores and bottom of the lakes. Research has analyzed the influence of the hydraulic connectivity of three lakes located in northern Poland on the structure of associated bottom invertebrates elements that monitor the conditions in habitats. The structure and functioning of ecosystems in wetlands, including in oxbow lakes, are direct or indirect in connection to fluctuations in water levels during floods or flow pulsations. Hydrological processes cause changes in the chemical composition of the water in oxbow lakes and sediment dispersion due to the exchange between water and sediments. In the lentic habitats (disconnected from the main river), the retention time is longer than in the semi- and lotic oxbow lakes whereas the productivity of the ecosystem is only internal and limited. The use of macrozoobenthos as bioindicators in re-connected oxbow lakes in small river valleys indicates that, on the long-term period (5 years), it does not have as a result the improvement of the environmental conditions of those habitats. This is shown by the monitoring indicators. The main reason seems to be the loss of the full connectivity between the oxbow lakes and the main river channel within 3 to 4 years, having as a result only systems of semilotic oxbow lakes and rivers. This hampers the free exchange of waters between ecosystems, the washing out of nutrients accumulated in sediments, the removal of bottom sediments, as well as the migration of hydrobionts. Therefore, the improvement of the ecological condition of the oxbow lake habitats and the permanence of those changes depend on the possibility of keeping the full hydrological connectivity to the river.

Results of multidisciplinary survey in the Laptev Sea in August-September, 2015

Data on oceanographic conditions and species composition of plankton, benthic and demersal fish and invertebrates are presented, obtained in the complex survey over the external shelf of the Laptev Sea in August-September 2015. The zooplankton abundance was low, with only local increases up to 400 mg/m 3 . Species diversity of fish and nekton invertebrates in the bottom trawl catches was low, too: 26 fish species and 2 species of cephalopods. Mean biomass of fish was estimated as 4.3 t/km 2 (in total 132 . 10 3 t within the surveyed area of 30,500 km 2 ). All fish species were distributed sparse. Arctic cod was the most abundant and occurred over the whole surveyed area, with large-sized fish dominating at the bottom and medium-sized (9-15 cm) fish - in the pelagic layer, other commercial species were greenland halibut and deepwater redfish caught on the continental slope. Bottom invertebrates in trawl catches were presented by 6 species of shrimp and 12 taxonomic groups of different rank, with predominance of starfish, brittle stars and sponges; gastropods were represented by 11 species, with Neptunea heros dominating by mass (42 %). Macrobenthos in samples of the bottom sampler was presented by 20 taxonomic groups, with predominance of polychaetes, bivalves and sipunculoids.

Supplements to the generalized quantitative assessments of benthic macrofauna in the Far-Eastern Seas and adjacent waters of the Pacific Ocean. Report 2. Regional and bathymetric features of biomass and density of its distribution for fish and some groups of invertebrates

Data on mean annual biomass (t) of the bottom macrofauna groups and main species in the Far-Eastern Seas and adjacent waters of the Pacific Ocean, by bathymetric ranges, and on density of their distribution (t/km 2 ) are summarized. The average density of distribution for bottom and demersal fish varies from 5.8 to 26.9 t/km 2 in the range 0-200 m, from 8.6 to 26.9 t/km 2 in the range 200-500 m, from 3.6 to 14.7 t/km 2 in the range 500-1000 m, and from 3.4 to 15.7 t/km 2 in the range 1000-2000 m. The average density for bottom invertebrates varies within 4.0-12.6, 4.7-19.6, 1.7-10.2, and 0.6-3.0 t/km 2 , respectively. The density usually increases in the transitional zone between the continental shelf and a slope (200-500 m). Aggregations of total macrofauna are the densest in this bathymetric range and reach 32.3 t/km 2 in the Bering Sea, 15.2 t/km 2 in the Japan Sea, and 41.4 t/km 2 in the Pacific waters at Kuril Islands. However, the concentrations in this zone in the Okhotsk Sea (maximum 13.3 t/km 2 ) and the Pacific waters at Kamchatka (31.5 t/km 2 ) are lower than that ones on the continental shelf.

Transfer of radiocaesium from contaminated bottom sediments to marine organisms through benthic food chains in post-Fukushima and post-Chernobyl periods

Abstract. After the earthquake and tsunami on 11 March 2011 damaged the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), an accidental release of a large amount of radioactive isotopes into both the air and the ocean occurred. Measurements provided by the Japanese agencies over the past 5 years show that elevated concentrations of 137Cs still remain in sediments, benthic organisms, and demersal fishes in the coastal zone around the FDNPP. These observations indicate that there are 137Cs transfer pathways from bottom sediments to the marine organisms. To describe the transfer quantitatively, the dynamic food chain biological uptake model of radionuclides (BURN) has been extended to include benthic marine organisms. The extended model takes into account both pelagic and benthic marine organisms grouped into several classes based on their trophic level and type of species: phytoplankton, zooplankton, and fishes (two types: piscivorous and non-piscivorous) for the pelagic food chain; deposit-feeding invertebrates, demersal fishes fed by benthic invertebrates, and bottom omnivorous predators for the benthic food chain; crustaceans, mollusks, and coastal predators feeding on both pelagic and benthic organisms. Bottom invertebrates ingest organic parts of bottom sediments with adsorbed radionuclides which then migrate up through the food chain. All organisms take radionuclides directly from water as well as food. The model was implemented into the compartment model POSEIDON-R and applied to the north-western Pacific for the period of 1945–2010, and then for the period of 2011–2020 to assess the radiological consequences of 137Cs released due to the FDNPP accident. The model simulations for activity concentrations of 137Cs in both pelagic and benthic organisms in the coastal area around the FDNPP agree well with measurements for the period of 2011–2015. The decrease constant in the fitted exponential function of simulated concentration for the deposit-feeding invertebrates (0.45 yr−1) is close to the observed decrease constant in sediments (0.44 yr−1). These results strongly indicate that the gradual decrease of activity in demersal fish (decrease constant is 0.46 yr−1) is caused by the transfer of activity from organic matter deposited in bottom sediment through the deposit-feeding invertebrates. The estimated model transfer coefficient from bulk sediment to demersal fish in the model for 2012–2020 (0.13) is larger than that to the deposit-feeding invertebrates (0.07). In addition, the transfer of 137Cs through food webs for the period of 1945–2020 has been modelled for the Baltic Sea contaminated due to global fallout and from the Chernobyl accident. The model simulation results obtained with generic parameters are also in good agreement with available measurements in the Baltic Sea. Unlike the open coastal system where the FDNPP is located, the dynamics of radionuclide transfer in the Baltic Sea reach a quasi-steady state due to the slow rate in water mass exchange in this semi-enclosed basin. Obtained results indicate a substantial contribution of the benthic food chain in the long-term transfer of 137Cs from contaminated bottom sediments to marine organisms and the potential application of a generic model in different regions of the world's oceans.

Feeding peculiarities of the juveniles of the Atlantic salmon (Salmo salar L.) infected with the invasive parasite Gyrodactylus salaris in the Keret River

Extremely low feeding intensity was registered for the juveniles of Atlantic salmon inhabiting the Keret River (the White Sea basin) and infected with the invasive monogenean Gyrodactylus salaris. This was due to the asthenia observed during the summer period. The infected fingerlings and parrs were characterized by single specimens of the bottom invertebrates in their guts (larvae of caddis flies, nymphs of stoneflies and mayflies, and mollusks). The stomach filling index in these specimens was five to seven times lower comparing to the healthy individuals inhabiting the Ponoi and Kachkovka rivers (Kola Peninsula). About one-third of the infected fingerlings had empty guts, which was never observed for the juveniles of the wild populations of Atlantic salmon during the summer growth period in the rivers of Karelia and the Kola Peninsula.

Feeding of blunt-snouted lenok Brachymystax tumensis Mori, 1931 (Salmoniformes, Salmonidae), in Korbokhon Lake (Left Bureya River, Khabarovsk Krai) in summer

Characteristics of feeding of blunt-snouted lenok Brachymystax tumensis in the mountain moraine Korbokhon Lake (Left Bureya River, Khabarovsk krai) in summer is presented. It was established that individuals at an age of 3+ to 13+ use all accessible seasonal types of preys both near bottom and in surface water layers as food. In total the contents of all studied stomachs, 88 components of animal origin (bottom invertebrates, lenok roe, larvae, pupae, and imagoes of aquatic and terrestrial insects), as well as three plant components, were found. With age, the spectrum of feeding of lenok widens. In stomachs of individuals at an age of 9+ to 13+, besides invertebrates, bearded stone loach Barbatula toni and fur small murine rodents were recorded. Selectivity of feeding with respect to weight and type of preys was revealed: lenok older than 9+ prefers larger food items; individuals at an age of 11+ to 12+ more frequently include beetles and other terrestrial insects in the diet, and the ratio of aquatic and terrestrial food items changes in favor of the latter.

Role of microhabitat heterogeneity in benthic faunal communities in sandy bottom sediments of Oura Bay, Shimoda, Japan

Habitat heterogeneity contributes to the maintenance of species diversity; however, little is known about the influence of microhabitat heterogeneity on the diversity of sandy bottom invertebrates. We tested the hypothesis that the structure of benthic faunal communities differs among microhabitats because each microhabitat function differs according to their physical properties. The descriptors of invertebrate assemblages (species richness, numerical abundance, and species composition) and physical properties (sedimentary organic matter content, sediment grain size, water temperature, and salinity) were determined monthly from April 2012 to March 2013 at 6 sampling stations (the stations were approximately 100–200 m apart) in the Oura Bay, Shimoda, Izu Peninsula, Japan. Species richness and numerical abundance of macrofauna varied significantly among stations, as well as the species composition. There were also significant differences in sedimentary organic matter content and grain size among the different stations. These results suggest that faunal distribution and environmental properties can differ at the microhabitat scale. Furthermore, multiple regression analysis revealed that a significant positive correlation existed between the sedimentary organic matter content and numerical abundance and, consequently, sandy bottom faunal communities were structured depending on the sedimentary organic matter content at the microhabitat scale. A diverse benthic faunal community is formed owing to the heterogeneity of microhabitats in sandy bottom sediments; thereby, further studies are required to characterize microhabitat differences.

Macrozoobenthos in the middle course of the Vyatka River in the area of a Chemical-Weapons Destruction Facility

The results of 5-year studies on macrozoobenthos in the Vyatka River in the area of the Chemical-Weapons Destruction Facility (CWDF) (settlement of Mirny, Kirov oblast) at the stage of neutralization of organophosphorous agents are presented. The taxonomic composition, dynamics of quantitative parameters, and structure of communities of bottom invertebrates are considered. A bioindicational assessment of water quality is made. The conservation of the total taxonomic richness and increase in the total biomass of zoobenthos are established. Processes of organic pollution and eutrophication in the Vyatka River are determined.