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Data on spatial distribution and habitat conditions are presented for walleye pollock Theragra chalcogramma at southern Kuril Islands in spawning season (spring 2015) and feeding season (summer 2016). In spring, walleye pollock are distributed over the entire shelf and continental slope down to 900 m depth and occupy the upper layer on the shelf and intermediate layer at the slope with water temperature 0.1–1.5 o C. In summer, they aggregate at the depth of 200–270 m beyond the shelf in the intermediate water at the Pacific slope of Iturup Island, under the temperature of 1.3–2.9 o C. Both spatial and bathymetric migrations of pollock are minimal at the Pacific side of Iturup, but they migrate for spawning westward and southwestward to the Okhotsk Sea and slope of Small Kuril Ridge where concentrate at the benthic front between the tidal mixing zone and the Intermediate water. Seasonal redistribution of walleye pollock is accompanied with changes of size-age structure in the main aggregations.

Dynamics of demersal fish biomass is considered on results of trawl surveys conducted in Peter the Great Bay (Japan Sea) in 1977-2015. Fishery did not have a significant impact on this complex of fish species, including both fluctuating species (walleye pollock, arabesque greenling, pacific herring) and species with stable stock, because of low intensity. Annual landings in the bay were much lower than recommended volumes (TAC). However, a tendency to the total biomass decreasing was observed, accompanied with growth of the sculpins (Cottidae) portion in the ratio of species biomass. The sculpins prey on juveniles of many other species, so maybe their higher abundance was one of reasons for general depletion of the benthic fish community. Other predators, as marine mammals, were not abundant in Peter the Great Bay. For rational resource management, the fishery impact should be distributed proportionally between populations, taking into account their state, so both traditional commercial objects and predators with growing abundance should be landed. This ecosystem approach requires permanent monitoring to all groups of fish species.

Aim.Identification of metal transference characteristics in components of the ecosystem of the north‐western part of the Caspian Sea. Material and Methods.Sampling was carried out according to generally accepted methods and the determination of heavy metals was carried out by atomic absorption spectroscopy using an atomic absorption spectrometer with electro‐thermal atomization MGA‐915 MD. Results. In studying the migration of trace elements in the trophic chains of the Caspian Sea sturgeon species it was found that: (a) chromium, manganese and iron do not accumulate along the trophic chain researched; (b) accumulation of lead and cobalt above the trophic level occupied by benthic invertebrates did not occur; (c) cadmium, nickel and copper were accumulated primarily by benthic organisms, while cadmium and nickel accumulated in the kidneys of Russian and Persian sturgeons and copper accumulated in the liver of both species (d) bioaccumulation of zinc occurs sequentially in the links: soil‐water‐benthic invertebrates‐benthophage fish (in Russian and Persian sturgeons in their kidneys, liver and muscles) and (e) mercury migrates along the links of the food chain, accumulation coefficients increasing progressively in the system: soil‐Didacna mollusc‐benthophage fish (in Russian and Persian sturgeons in their kidneys, liver and muscles). Conclusion.The accumulation of heavy metals from water amongst aquatic organisms depends on the properties of the metal, its involvement in biochemical processes, species, biological status and the nature of abiotic living conditions.

Aim.The littoral fauna of the Far East Marine Reserve was studied at the end of the last century; however, the monitoring studies of the malacofauna are relevant because of the increased recreational load and the threat of new species introduction. The aim of the work is to update the data on species composition and distribution of gastropods and bivalves on the littoral zone of the reserve.Methods.The material was collected during the monitoring studies in 2012-2014. The compilation of the collections and identification of the species were carried out according to standard methods. For the definition, conventional determinants and atlases were used.Results.As a result of the research, 49 species and taxa of mollusks were found, including 33 gastropods and 15 species and 1 hybrid of bivalves. New for the littoral fauna of the reserve were 13 species of Gastropoda, 3 species and 1 hybrid Bivalvia. It was established that the introduction of Atlantic mussel Mytilus galloprovincialis into benthic communities occurs through its hybridization with native species.Conclusion.The data obtained allows us to present a more complete picture of the biodiversity and distribution of the littoral malacofauna of the reserve, an integral part of Peter the Great Bay.

Zooplankton in the eastern Chukchi Sea is described on the data of summer observa­tions in 2017. The northern part of the surveyed area was occupied by the cold water masses from the Arctic Ocean and Beaufort Sea. Large-sized zooplankton dominated here, including copepods Calanus glacialis , C. hyperboreus (this species is an indicator of Atlantic waters) and cold-water hyperiids Themisto libellula. In the southern part of the surveyed area, small-sized zooplankton dominated by biomass and abundance and species belonged to the Bering Sea community, as copepods Calanus glacialis + Calanus marshallae , Eucalanus bungii , and Metridia pacifica , were presented in the large-sized fraction. In the western part of the sur­veyed area and in the coastal waters, small-sized copepods Pseudocalanus spp. and Oithona similis prevailed, and biomass and abundance of neritic species as Centropages abdominalis and Acartia longiremis were high, too. Besides, some species typical for desalinated water were observed here ( Eurytemora herdmani , Podon sp., and Epilabidocera amphitrites ), as well as larval forms of benthic invertebrates (larvae of polychaetes, bivalves, gastropods, and echinoderms). Arrowworms Sagitta elegans were abundant everywhere that was caused by this species reproduction. The observed structure of plankton community corresponded to feeding demands of arctic cod juveniles, but the zooplankton biomass was rather low. These features of community could be interpreted as early summer state, when its biomass does not reach the maximum yet, as it was observed, for example, in September 2007.

Current state of zoobenthos in the areas of scallop Chlamys islandica beds in the southern Barents Sea and eastern White Sea (Voronka) is described. The scallop stock is ex­ploited there with the landing by specialized vessels, without separation of catch, so bycatch of other species is considerable. As the result, significant changes occurred in structure of benthic communities during the times of scallop fishery. To assess the fishery effect, species composition of benthos, its dominant species and trophic structure is considered separately for 4 regions with different degree of exploitation. Dynamics of zoobenthos abundance is traced over the last 25 years. Changes in trophic structure of the benthic community at Cape Svyatoy Nos (southern Barents Sea) are analyzed in details. Although up to ¼ of its total biomass is presented by carnivorous species and the biomass of C. islandica has decreased, the portion of sestonophages has increased in this community. Recently a recovery of zoob­enthos is observed in its southern part, supposedly because of the animals redistribution from adjacent areas unaffected by fishery. On the contrary, extremely low biomass of zoobenthos, in particular scallop, is observed in the northern part of the community. Biomass of benthos in the Voronka area is high, but it is formed mainly by mussels. There is concluded that more than a decade is required for full recovery of the scallop stock and accompanying zoobenthos communities to the native state.

We consider the dynamics of the sediment chemical composition and benthic community state in different areas of Lake Onega in the last 20–25 years. It is shown that the combined effect of anthropogenic factors and climate changes has caused a profound transformation of deepwater benthic communities. The upper parts of the northwestern bays (Kondopozhskaya and Petrozavodskaya bays), where the effect of anthropogenic factors is the most manifested, are referred to the most contaminated (first) zone. In these areas, structural adjustments of bottom cenoses are noted; they are the dominance of resistant representatives of oligochaetes and chironomids and the absence of relict crustaceans. The sediments of the first zone are characterized by the greatest content of organic matter, reduced values of pH and Eh, the presence of toxic agents (in Kondopozhskaya Bay). In the buffer areas of the north-western bays referred to the second zone the anthropogenic effect is weakened by the influence of oxygen-saturated waters passing from the adjacent open areas of the lake. The bottom sediments of the buffer zones are characterized by a deeper oxidized layer and the maximum development of amphipods. The central deep-water areas of Lake Onega (the third zone) are currently the least affected by the anthropogenic factor. The sediments in the central zone are characterized by the minimum content of organic matter, the presence of ore crusts (containing iron and manganese), which determine the poor development of benthos here. In 1998–2016 in all studied areas of Lake Onega classified as three zones a decrease in the numbers and biomass of benthos occurred, which led to a decrease in its production by 2–4 times. It is suggested that the decline in benthic community indicators is caused by the suppressive action of iron, which is accumulated in sediments. The reason of that is an increasing input of this element with river waters as a part of humic substances due to climatic changes in the catchment area.

New data are presented on qualitative and quantitative composition of forage benthos obtained in hydrobiological surveys in the lower Don River in 2016. The area from Semikarakosk to the mouth (193 km), including the Don estuary, was surveyed. The benthos was sampled by Petersen dredge of 0.025 m 2 ; in total 60 samples were processed, with some replicate ones. Mollusca was the main group of the forage benthos both in May, June, and September, mostly due to high abundance of zebra mussels. The biomass of forage mollusks varied in the range of 1.3-104.3 g/m 2 , with the maximum in September after settling of D. polymorpha and D. bugensis juveniles. The biomass of “soft” forage benthos (mainly oligochaetes and chironomids) ranged from 6.3 to 12.6 g/m 2 . By quantitative abundance of benthic fauna, the feeding capacity of the lower Don is assessed as high.

Underwater observations were conducted to assess the impact of the research Danish seine elements on behavior of walleye pollock Theragra chalcogramma in its active zone. The underwater video equipment was installed on specially designed and constructed experimental platform and on elements of the Danish seine. In the experiment with pollock, the experimental platform demonstrated its low efficiency, however, it could be used for observations on sedentary benthic organisms on homogeneous soils without sharp changes in the terrain. With the equipment installed directly on the Danish seine, high efficiency of the seine ropes was observed: up to 92 % of fish from encircled volume remained in the towed area. Taking into account this estimation and features of fish biomass distribution, the coefficient of catchability for Danish seine is determined as 0.40 ± 0.15.

Data on oceanographic conditions, composition of plankton communities, benthic and demersal fish and invertebrates in the southern East Siberian Sea are presented by results of the complex survey conducted in August 2015, The bottom trawl survey assessed 10 species of fish and 3 species of jellyfish with total biomass 1900 t. Arctic cod Boreogadus saida dominated absolutely in the benthic ichthyocenose (60.6 % of the total biomass). Besides, 3 species of shrimps, 1 crab species, 4 species of gastropods, and 6 other taxonomic groups of macrobenthos including starfish and isopods were found in trawl catches, with the average biomass of macrobenthos 41.7 kg/km 2 . In the bottom samples of macrobenthos, 12 taxonomic groups were presented, with predominance of bivalves, polychaetes, isopods, and amphipods (summary 95 % of the total biomass).

Taxonomic and quantitative composition of Foraminifera assemblages in the Zhitkov Bay (Russky Island, Peter the Great Bay, Japan Sea) are described. In total, 52 species from 30 genera and 14 families of benthic foraminifera have been identified in bottom sediments. The most of them are represented by calcareous forms (38 species), with the highest abundance of families Elphidiidae, Discorbidae, and Buliminidae, other are 14 species of agglutinated foraminifera, including 2 common species of families Trochamminidae and Ataxophragmiidae. Population density of benthic foraminifera correlates well with the type of bottom sediments: the highest abundance is observed on alenric sediments and pebble-sandy grounds and the lowest abundance - on fine-grained pelitic sediments. Six assemblages of benthic foraminifera are determined for the Zhitkov Bay, taking into account the prevailing families.

Quantitative characteristics of microbial community, algal periphyton and macrozoobenthos are presented for two tributaries of the Lyutoga River, as the Partizanka River (pink salmon spawning stream) and the Frikena River (without steady spawning grounds), on the base of surveys conducted in July-October, 2011. Number of benthic bacteria in the bottom grounds varied in the range 1.1-4.0 · 10 6 cells/g in the Frikena and 0.8-11.1 · 10 6 cells/g in the Partizanka. Oligocarbophilic microorganisms prevailed in the bacterial benthos of both rivers before the beginning of active salmon spawning (July- August), developing mainly on autochthonous organic substrates. In September, with appearance of salmon carcasses after spawning, total abundance of the microorganisms increased and the portion of ammonifying bacteria basing on this allochthonous organic matter became higher in the Partizanka. Algal periphyton biomass changed from 7.8 to 117.0 g/m 2 in the Frikena River and from 0.5 to 305.6 g/m 2 in the Partizanka River, with diatoms domination in both streams. Periphyton in the Partizanka was destroyed by flood in September but successively recovered by October, with multiple increasing of the algal biomass, obviously due to influx of nutrients in the process of salmon carcasses decomposing. Biomass of macrozoobenthos was 5.1-21.0 g/m 2 in the Frikena River and 2.2 to 3.7 g/m 2 in the Partizanka River, in both tributaries its dynamics was determined mainly by life cycles of aquatic insects.

The development of the biotic community on the artificial reefs in the coastal zone of the northeast Black Sea region has been studied. Colonization stages of the artificial reefs by hydrobionts depended on substance, time and depth of reef construction have been considered. Reef colonization by fouling organisms is a biotic primary succession of the benthic mature community. It has been found that in 2–3 years on an artificial reef species diversity and biomass of aquatic organisms rise sharply and reef biocenose becomes a powerful biofilter involved in the process of environment self-purification. The results of the functioning of the reef biocenose can serve as a basis for using artificial reefs in biological treatment of water in the coastal zone. Ключевые слова: биоремедиация, прибрежные экосистемы, искусственные рифы, рифовый биоценоз, биофильтрация, биологическая очистка, Черное море.

Aim. We present the findings of studies of the current state of benthic fauna of the Volga delta channels by the structure of benthic communities. The study has been carried out in the framework of researches by FSBSI "Caspian Fisheries Research Institute" conducted in the period from 2010 to 2014. The main goal was to assess the current state of benthic fauna of output channels of the Volga delta areas against the backdrop of changing water availability of the Volga river. Methods. We have conducted sample processing of zoobenthos within investigated watercourses of the Volga River according to conventional methods of Zhadin V.I. (1960), Winberg G.G. (1984) and Abakumov V.A. (1992). Results. The results of the work on the study of the modern state of the benthic fauna of the Volga delta channels show that the species composition of macrozoobenthos in these sections of the river in dry years was characterized by mass development of oligochaetes. With the increase of water content (between the years 2012 and 2013) in all studied water streams there is a change of the dominant group. With the decrease in the annual runoff (in 2014) the qualitative characteristics of zoobenthos have changed. In the average long-term aspect, the distribution pattern of quantitative indicators of benthic invertebrates in the delta of Volga river was uneven, and their greatest density has been marked in the wet year. Main conclusions. Thus, the research found that increase of the water content of the Volga River positively influences the hydrobiological picture in the output channels of the delta of the Volga River.

Species composition of macrozoobenthos in lagoons of Sakhalin Island (in total, 637 species) is described on the base of cited data and results of author’s surveys. Its species composition is formed under influence of wide spectrum of environmental factors, as size of lagoon, water salinity, periodicity of connection with the sea and type of the water exchange, river discharge regime, climatic and geographical isolation, etc. Generally, 6 types of lagoons are determined on the coast of Sakhalin differed by composition of benthic fauna: 1) large semiclosed salty lagoon (Lake Busse in southern Sakhalin); 2) small semiclosed salty lagoons with water stratification and periodic connection with the sea (Lake Izmenchivoe and Lake Ptichye in southern Sakhalin); 3) large shallow semiclosed lagoons (in northern Sakhalin); 4) small isolated brackish lagoon (Kuegda Bay in northern Sakhalin); 5) closed oligosaline lagoons (Lake Tunaicha and Lake Aynskoe in southern Sakhalin); 5) isolated freshwater lagoons (Vavaysko-Chibisanskaya lake system in southern Sakhalin). Salty and freshwater lagoons are distinguished by the highest species diversity.

The article discusses the role of marine mammals in marine and oceanic ecosystems on the example by Far Eastern seas with adjacent waters of the North Pacific, one of the regions of the World Ocean distinguished for high biological and fish capacity along with a high abundance of cetaceans and pinnipeds. Based on extensive data, published mostly by Russian experts, the authors calculated the following quantities of annual consumption of fish and invertebrates by marine mammals in the three Far Eastern seas: 14.6-18.2 million t in the early 20 th century, 12.3-15.1 million t in the late 1970s, 22.7-28.8 million t in the pre-harvesting period, and 24.0-24.7 million t in the early 21 st century (27.0-29.5 million t, if 3-5 million t in ocean waters off the Kuril Islands and Kamchatka are taken into account). More than a half of this quantity is composed by zooplankton and zoobenthos, and then by fish and squids. In too time scales of food consumption by fishes and large-sized invertebrates are much higher than these estimates: in the layer 0-1,000 m, 516 million t was consumed in the 1980s-1990s, 389 million t in 1991-1995, and 461 million t in 1996-2005. In the years of high abundance, large-sized walleye pollock alone consumed nearly 40 million t of small-sized fish and squid. Based on the data of 35-year-long ecosystem studies by TINRO-Center, the following biomass estimates have been obtained for the biota of the Far Eastern Economic Zone of Russia: 1,000 million t of meso- and macroplankton, 500 million t of zoobenthos, 100 million t of nekton, 5 million t of benthic fish, and 2.43 million t of large-sized benthic invertebrates, which are not included in the benthos. Against the background of these estimates and comparing the volume of food consumption by marine mammals concluded that marine mammals in the Far Eastern Russian waters noticeable in food webs, but their role does not rise to a level sufficient for the regulation of the powerful sea and ocean makroekosistem.

The results of research done by CaspNIRKh on the development and spatial distribution of macrophyto-and zoobenthos in the northwestern part of the Caspian Sea are presented. Data on seasonal and long-term dynamics of biomass and species composition of phytocenosis together with other environmental factors such as salinity and a type of sediments show the state of benthic ecosystems in that part of the sea. Data obtained on the development of benthic communities reveal eutrophic areas for feeding commercially valuable fish species and estimate the carrying capacity of the sea (when introducing artificially reared juveniles).

Aim. Industrialization of Caspian oil and gas supplies requires a serious approach to the problem of protecting and preserving the region’s unique environment that, in fact, represents a property of international commons. The article studies into the impact of the Caspian modified waters on the benthos faunistic composition. Methods. Zooplancton and zoobenthos hydrobiology material was collected in the Central Caspian survey loop. Samples were collected in spring and summer in 2002 – 2007 in the western part of the Caspian Sea (Dagestan offshore location of the Caspian Sea from Smirnovsky Midstream Sandbank and Pearl Bank till Derbent latitude) on “Tsada” vessel. They were collected from 25 stations located on ten standard parallel latitude logs with depth scope of 8–100 m from 0, 10, 25, 100 m horizons. These samples were used as a material for characterizing phyto- and zooplankton. Results. The benthic can be considered the most stable communities of the marine environment as they are the most resilient to quantity and modifications. Heterogeneous and variable ecosystem (biotope) is typical of the areas with strong currents as the organic quality, quantity and physic-chemical properties are marked by variability. Location. The Caspian zoobenthos state as well as the features of the Caspian Sea benthos communities characterize the ecology of the Caspian Sea and give a true view of the situation in the drilling sites. This will help predict and avert negative effect of hydrocarbon production on the Caspian Sea ecosystem. Main conclusions. Water modification must be intensive, long-lasting and frequent for it to have an impact on benthos.