Bottom Animals Research Articles

Hydrobiological characteristic of small lakes in northern Karelia during the ice-covered period

The life of lakes in winter is still insufficiently studied. The purpose of this article is a comparative analysis of the quantitative development of planktonic and benthic communities and the abiotic conditions of their existence during the ice-covered period in two small (<1 km2) northern lakes that differ greatly in morphometry and the degree of water humification. A significant difference was revealed in the seasonal dynamics of plankton communities in the studied lakes. In a deeper lake with water uncolored by humus, the quantitative development of phytoplankton at the end of the ice-covered period was almost as significant as during the open-water period. It is necessary to note the rapidity of changes in under-ice phytoplankton in early spring: in April 2020, the content of chlorophyll a in water changed more than six times during a week. There was no mass development of phytoplankton under the ice in a shallow highly humified lake. The zooplankton of the studied lakes was characterized by the opposite trend. In the deep-water lake, the winter zooplankton was noticeably inferior to the summer one in terms of the level of quantitative development; in the shallow lake, a high biomass (~1 g/m2) of zooplankton was noted throughout the entire study period. The macrozoobenthos of lakes in winter, on the whole, retained the same high level of quantitative development as in the open-water period. Seasonal differences were local and were caused by the redistribution of bottom animals due to changes in the oxygen and, possibly, temperature regime of bottom waters. In particular, due to hypoxic-anoxic conditions at the end of the ice-covered period, benthic animals migrated from the profundal zone of the deep-water lake. After the ice melted and the near-bottom waters were saturated with oxygen, the profundal community quickly recovered. Thus, the quantitative development of biological communities in winter can vary greatly even in closely located lakes, in particular, it depends on the degree of humification of the water body. Given the high dynamism of phytoplankton in early spring, the assessment of the role of the under-ice period in the life of lakes, apparently, requires long-term research, including detailed observations at the end of ice-covered period.

Community structure of macrozoobenthos in seagrass bed on Barrang Lompo Island

Macrozoobenthos are bottom animals that play an important role in the productivity of waters in seagrass beds. This study aims to determine the species composition, density of macrozoobenthos, community structure of macrozoobenthos and the relationship between seagrass density and density of macrozoobenthos. The research method used is purposive sampling method, this method is taken based on certain reasons and criteria. This research was conducted in June-July 2022 on Barrang Lompo Island. Sangkarrang District, Makassar City. There were 26 species found consisting of 4 classes namely Bivalvia, Gastropods, Chepalopods and Crustacea with a total of 283 ind and dominated by the Gastropod class, both from the number of species and individual density. Macrozoobenthos community structure on Barrang Lompo Island at station I and II with a moderate diversity index (H'), moderate uniformity index (E') and low dominance index (D). The types of seagrass found at stations I and II were Enhalus acoroides, Thalassia hemprichii, and Cymodocea rotundata. The regression results of the relationship between seagrass density and macrozoobenthos density on Barrang Lompo Island show a weak relationship, which means that seagrass density has no relationship with macrozoobenthos density but macrozoobenthos density is influenced by physical and chemical factors of the waters and the type of sandy substrate.

Bottom‐up as well as top‐down processes govern zoobenthic secondary production in a tidal‐flat ecosystem

AbstractFor decades, we monitored numbers and weights of the macrozoobenthos in a vast tidal‐flat area in the Dutch Wadden Sea. We used data collected since 1992 to estimate annual secondary production. Data on chlorophyll concentrations and primary production were available for a nearby tidal inlet, showing rapid increases in the late 1970s and gradual declines since the late 1980s. The benthos responded with a doubling of biomass around 1980 and gradual declines of summer biomass, annual production as well as seasonal biomass gain for the 1992–2019 de‐eutrophication period. In nearly all years, production of bivalves (on average 25.5 gAFDM m−2 yr−1) accounted for more than half of the total zoobenthic production (averaging 42.7 gAFDM m−2 yr−1). Production values for individual years were not correlated with chlorophyll concentrations or primary production of that year, but did show a significantly positive relationship with bivalve recruitment success in the preceding year. As recruitment was governed by predation pressure on early bivalve bottom stages, it is a top‐down process. Bottom‐up processes were expressed in the gradually declining long‐term trend of bivalve growth rates and secondary production during the de‐eutrophication period and also in a few years when bivalve numbers were so high that growth rates were reduced by food competition. In by far most years, numbers of bottom animals were too low to fully exploit the carrying capacity of the system and production increased linearly with preceding recruitment.

Summer-fall macrozooplankton assemblages in a large Arctic estuarine zone (south-eastern Barents Sea): Environmental drivers of spatial distribution

Macrozooplankton assemblages were studied during the summer and fall of 2012 in the Pechora Sea, a large coastal region of the south-eastern Barents Sea strongly affected by discharges of freshwater. Sampling was performed at 23 stations with 550-μm mesh IKS-80 nets. We focused on macrozooplankton and large (>1.5 mm) non-copepod zooplankton (larvae of benthic animals and medusae). A combination of multivariate cluster analysis, diversity indices and canonical correspondence analysis was used to relate the spatio-temporal patterns of the zooplankton assemblages to environmental factors. Summer macrozooplankton density varied from 3 to 928 ind. m−3, averaging 131 ± 49 ind. m−3, with medusae being the most numerous (mean ± SE: 67.9 ± 7.8% of the total abundance). The total macrozooplankton biomass ranged from 0.3 to 516 mg dry mass (DM) m−3 with a mean value of 28 ± 25 mgDM m−3. There was a clear decline in the total macrozooplankton abundance (1.1–6.0, 4.4 ± 1.6 ind. m−3) and biomass (0.4–2.7, 1.2 ± 0.7 mgDM m−3) in fall when only two taxa (Parasagitta elegans and Mertensia ovum) were identified. Cluster analysis revealed three groups of stations in summer. The clusters were similar in terms of the abundance in common taxa but differed by the total density, biomass and diversity. We found that the offshore zone was dominated by the euphausiids Thysanoessa spp. and the chaetognaths Parasagitta elegans while the coastal area was characterized by high density of hydromedusae and larvae of bottom animals (Hyas spp., Pagurus spp.). There was a significant decline in the total macrozooplankton abundance and biomass from summer to fall. Canonical correspondence analysis showed that during the summer and fall of 2012, 68% of macrozooplankton variability was explained by environmental factors with water temperature and longitude being the most important. The distribution of macrozooplankton taxa was also related to local circulation patterns and possibly to mesozooplankton as potential prey for carnivorous taxa. Our data may be useful for future monitoring in the coastal Arctic estuarine regions.

Taxonomic structure of the zoobenthos of the Lukoml GRES cooling reservoir

The species composition of zoobenthos in the heated and non-heated zones of the cooling lake Lukoml State District Power Station was studied. 80 taxa of bottom animals have been registered, and two new species of chironomid larvae have been identified. The bottom fauna includes a protected relict species of Pallaseopsis qudrispinosa, which is preserved in the conditions of warming.it is listed in the Red book of Belarus and the alien species – freshwater shrimp Macrobrachium nipponense. The high taxonomic diversity indicates that the Lukoml State District Power Station operation has little impact on the bottom community throughout the lake’s water area. However, species richness is reduced locally by half in the zone of influence of heated water discharge, especially in summer. Under the influence of heating, the taxonomic structure and spatial distribution at different depths change.

ДОННАЯ ФАУНА НЕКОТОРЫХ ОЗЕР УЗБЕКИСТАНА

Species composition of macrozoobenthos of 6 lakes from different regions (north, center, south) of the republic have been studied. Total 111 species of bottom animals have been recorded. List of dominant species is presented. Using coefficient of Sörensen-Czekanowski similarity of species composition of macrozoobenthos of the lakes studied have been determined.

Restoration of Zoobenthic Communities and Water Quality in the River Ecosystem after a Decrease in the Level of Organic Pollution

The development of principles and methods for restoring ecological systems that have undergone intense anthropogenic impacts is one of the most important tasks of modern ecology. This work is devoted to studying the regularities of the influence of organic pollution on the structure and functional characteristics of zoobenthic communities and the degree of restoration of the pristine communities of bottom animals and the quality of the waters of the small Izhora River by bioindication characteristics. For this, the results of studies from the 1970s and 2000s were compared. Intensive organic-matter pollution influenced the structure and functioning of zoobenthos, increasing biomass and energy flow through the bottom animal communities. At the same time, the role of oligochaeta worms in the bottom communities sharply increased, the role of larvae of amphibiotic insects decreased, the species richness and biological diversity of zoobenthos declined, and the efficiency of energy transfer between trophic levels of primary and secondary consumers fell. Water quality in accordance with the values of the integrated index IPʹ corresponded to the fifth highest class of pollution (dirty). Downstream, due to self-purification processes, the water quality and ecosystem state improved slightly, but this improvement was not very significant, which indicated that the river ecosystem was not able to process excess organic matter entering the river. The introduction of wastewater treatment from organic pollutants at sewage treatment plants contributed to the restoration of the structural and functional organization of zoobenthic communities and significantly improved the state of the river ecosystem. However, a complete restoration of water quality did not occur: it improved to moderately polluted.

Responses of Aquatic Organisms to Cyanobacteria and Elodea in Microcosms.

The aim of the present study is investigation of the impact of mass development of cyanobacteria and Elodea on population characteristics (abundance, biomass, fecundity) and "health" parameters (the state of embryos, heart rate, and thermal resistance) of aquatic invertebrates in experiments with controlled conditions. In July-August 2018, in four variants of microcosms, the conditions were modeled characteristic of the coastal zone of the Rybinsk Reservoir in the period of mass development of cyanobacteria. Mass species were placed in microcosms of planktonic (with domination (80%) Daphnia longispina) and bottom animals (Unio pictorum, Gmelinoides fasciatus, Asellus aquaticus), as well as Elodea canadensis. In the variants with cyanobacteria, the toxic microcystins LR were revealed (24-53% of the sum of toxins, or from 6.6-66.5 μg/L). The presence of cyanobacteria (Aphanizomenon flos-aquae, Microcystis aeruginosa, and Gloeoitrichia spp.) influenced structural parameters of plankton: the quantity to green algae decreased, small-sized crustaceans increased. Influence of cyanobacteria caused reliable changes in parameters of aquatic animal from those of the control: thermal resitance of mollusks and amphipods decreased, time of restoration of heart rate after loads (salinity test) in mollusks increased; in amphipods, individual fecundity decreased, frequency of abnormalities and of mortality of embryos increased. The presence of Elodea intensified these effects. Thus, mass development of cyanobacteria and Elodea influences ecological-physiological parameters of aquatic animals, decreasing their adaptivity to natural stresses and deteriorating the quality of the progeny.

Present geoecological transformations in the Kerch strait ecosystem

This study examined the distribution, structure, and dynamics of bottom communities of macrozoobenthos in the Kerch Strait based on an analysis of literature sources from 1934 and 1955, archival data documenting hydrobiological field investigations of the Southern Research Institute of Marine Fishery and Oceanography (YugNIRO, Kerch) in 1986 and 1989, and results of the joint Russian-Ukrainian benthic survey of the Kerch Strait (47 stations) conducted by the Institute of Geography of RAS and YugNIRO in the summer of 2010. It was found that populations of filter-seston feeding bivalves in the strait ecosystem have degraded over the past 75 years, whereas populations of detritus-feeding polychaetes preferring muddy bottoms have become much more abundant. Researchers identified species of bottom animals and strait areas exhibiting maximum changes. An analysis of the dynamics of bottom sediment structure in the strait based on YugNIRO archival data and the results of a 2008 diving survey conducted by the Institute of Geography of RAS (49 divers) demonstrated that the observed transformations are associated with silting of a considerable part of the strait bottom as a result of both earlier and more recent economic activities, particularly the disposal of dredging grounds from 1960 to 1990 and the construction of the Tuzla Dam in 2003, respectively. However, the character of the fixed transformations does not enable us to identify the specified reasons as the sole causes of the changes; therefore, the authors also consider hypotheses explaining other mechanisms. The authors conclude that further research on geoecological dynamics of the Kerch Strait ecosystem is needed, particularly after the construction of the Crimean Bridge.

MODERN GEOECOLOGICAL TRANSFORMATIONS IN THE KERCH STRAIT ECOSYSTEM

This study examined the distribution, structure, and dynamics of bottom communities of macrozoobenthos in the Kerch Strait based on an analysis of literature sources from 1934 and 1955, archival data documenting hydrobiological field investigations of the Southern Research Institute of Marine Fishery and Oceanography (YugNIRO, Kerch) in 1986 and 1989, and results of the joint Russian-Ukrainian benthic survey of the Kerch Strait (47 stations) conducted by the Institute of Geography of RAS and YugNIRO in the summer of 2010. It was found that populations of filter-seston feeding bivalves in the strait ecosystem have degraded over the past 75 years, whereas populations of detritus-feeding polychaetes preferring muddy bottoms have become much more abundant. Researchers identified species of bottom animals and strait areas exhibiting maximum changes. An analysis of the dynamics of bottom sediment structure in the strait based on YugNIRO archival data and the results of a 2008 diving survey conducted by the Institute of Geography of RAS (49 divers) demonstrated that the observed transformations are associated with silting of a considerable part of the strait bottom as a result of both earlier and more recent economic activities, particularly the disposal of dredging grounds from 1960 to 1990 and the construction of the Tuzla Dam in 2003, respectively. However, the character of the fixed transformations does not enable us to identify the specified reasons as the sole causes of the changes; therefore, the authors also consider hypotheses explaining other mechanisms. The authors conclude that further research on geoecological dynamics of the Kerch Strait ecosystem is needed, particularly after the construction of the Crimean Bridge.

Influence of the environmental factors on species diversity and quantitative development of zoobenthos in the Neva Bay

Hydrochemical characteristics, primary production of plankton, taxonomic composition, species richness, species diversity and quantitative characteristics of the benthic fauna of the Neva Bay had been collected and analyzed at the end of July and the very beginning of August 2003–2012 by the method stepwise regression, calculated equations with a free constant. Effects of biotic and abiotic factors on the structural and functional characteristics of benthic communities in the Neva Bay were evaluated using multiregression analysis. Research period had been accompanied by revival of industry of Saint-Petersburg, construction of ports, active navigation, development of Sea facade and completion of the construction of the St. Petersburg Flood Prevention Facility Complex and a large-scale hydrotechnical works: building of a Marine Multifunctional Reloading Complex (MMRC) “Bronka” and approach fairway to it. Results of statistical analysis showed that the number of species and species diversity of bottom animals in the Neva Bay declined with increased primary production and chlorophyll a concentration. Analysis of the factors influencing the values of biomass of benthic animal communities shows that these characteristics increased with growing chlorophyll concentration. During the anthropogenic stress of 2006–2007, the existing links between the structural characteristics of the zoobenthos and the functional biotic characteristics of the Neva Bay were completely destroyed. Restoration period 2008–2012 was accompanied by an increase in the species richness and species diversity of zoobenthos to the level observed before anthropogenic stress.

Sponge-collecting from a drifting ice floe: the Porifera obtained in the Kara Sea by the Dutch Polar Expedition 1882-83

Sponges from the Kara Sea (Arctic Russia) collected by the Dutch Polar Expedition 1882-83 are identified and discussed. The expedition experienced an unfortunate course of events, as the research vessel RV ’Varna’ was ice-bound and eventually got crushed by ice, leaving the crew and the scientists stranded on an ice floe drifting around in the Kara Sea. The scientists still managed to do many observations and made collections of bottom animals lowering collecting gear through a hole in the ice. After being enclosed for more than a year in the ice, the men travelled in small boats and sledges to the mainland of Russia and from there returned home. The zoological collections were brought to Copenhagen by the Danish research vessel RV ‘Dijmphna’, from where the material was picked up by the Dutch scientists. Most animal groups were subsequently discussed in a series of papers published in the Bijdragen tot de Dierkunde volume 14 (1887). The sponges of the Dutch Polar Expedition were in a rather bad condition when they arrived in Amsterdam and possibly for that reason were largely ignored. They nevertheless appear to be interesting and are here presented as a belated contribution to the 1887 issue, including the description of a species new to science, Lycopodina ruijsi sp. nov. The results are discussed in the framework of our present knowledge of the sponge fauna of the Kara Sea. In Appendix ten already known species are briefly described and SEM images of their spicules provided as a contribution to Kara Sea sponge morphology,

Geography of Macrozoobentos of Kerch Channel: Dynamics of Distribution, Structure and Indexes of Development Level

According to literature data and data from the South Scientifi c Institute of Fishery and Oceanology investigations a retrospective (1934, 1955, 1986, 1989) analyses of distribution, structure and dynamic of the bottom macrozoobentose community in Kerch Channel of the Black sea was made. Their present condition are evaluated according to the results of the summer joint Russian-Ukrainian bentos survey of 2010. Considerable changes in the character of distribution and structure of biocenois of bentos organisms for the last 75 years were foundid. Species of the bottom animals and areas of the channel, where their maximum degradation was happened were revealed. Possible mechanisms of fi xed hydrobiological transformations are proposed.

How imputation errors bias genomic predictions

The objective of this study was to investigate in detail the biasing effects of imputation errors on genomic predictions. Direct genomic values (DGV) of 3,494 Brown Swiss selection candidates for 37 production and conformation traits were predicted using either their observed 50K genotypes or their 50K genotypes imputed from a mimicked 6K chip. Changes in DGV caused by imputation errors were shown to be systematic. The DGV of top animals were, on average, underestimated and that of bottom animals were, on average, overestimated when imputed genotypes were used instead of observed genotypes. This pattern might be explained by the fact that imputation algorithms will usually suggest the most frequent haplotype from the sample whenever a haplotype cannot be determined unambiguously. That was empirically shown to cause an advantage for the bottom animals and a disadvantage for the top animals.

Macrobenthos of the Novaya Zemlya Trough

During the 54th cruise of the R/V Akademik Mstislav Keldysh the macrobenthos of the Novaya Zemlya Trough was studied using a Sigsby trawl along the submeridional transect near 75°30′N latitude at a depth range from 68 to 362 m. In total, 140 species of bottom animals were found. The relative role of the taxons was assessed using three indices: the number, biomass, and energy flow. Similarity indices were used for the comparison of the samples. The new material greatly contributes to the data on the composition of the fauna and the structure of the communities of the studied region. It was revealed that small scyphozoid polyps and sipunculoids play an important role in the trough’s community. The presence of the community dominated by Ophiocten sericeum (with the important role of small bivalves) was revealed for the first time not only at the eastern by also at the western slope of the Novaya Zemlya Trough. The sharpest changes in the composition and structure of the bottom community were confined to the zone of the transition from the trough floor to the slope. These changes are determined by the specificity of the macrorelief (of the floor and slope), the composition of the ground (soft brown silts abound in rhizopods and dense gray silts with an admixture of pebbles), and possibly by the hydrodynamic processes near the bottom.

Biological diversity and the community structure of organisms

Biological diversity and the complexity of the community structure of benthic animals in different bodies of water are evaluated using the Shannon index. The literature data on the communities in Lake Krasnoye (Karelian Isthmus, Leningrad Oblast), Shchuchy Bay of Lake Ladoga, Neva Bay, and the eastern part of the Gulf of Finland have been analyzed. The extrema (maxima and minima) and the inflection point of the curve of functions are determined with the help of derivatives. The rate of the secondary succession is evaluated for the first time by the example of benthic communities. It is shown that the community structure of bottom animals in the Shchuchy Bay ecosystem formed in the process of succession proves to be more complex than in Lake Krasnoye and the Neva Bay communities that have been formed for a long time. Communities of bottom animals are less complex in polluted waters of the top of the eastern part of the Gulf of Finland. It has taken 12 years to reach the maximum diversity of the bottom animal communities in Shchuchy Bay, 16 years in Lake Krasnoye, and 7–10 years in Neva Bay. It is supposed that, under favorable conditions in the waterbodies of a moderate climate and in the absence of heavy pollution or eutrophication, it takes 12–14 years on average to form the most complex community structure of bottom animals (3–4 bit/spec.). The structure of communities in polluted waters remains simple.

Changes of biological communities in the Eastern Gulf of Finland during the last century

Changes in biological diversity of the Neva Estuary (eastern Gulf of Finland), which is one of the largest Baltic estuaries, were assessed by means of BSRP SGEH priority indicators. They include macrophytobenthos, macrozoobenthos, alien species, ichthyofauna, avifauna, mammals and a portion of the territory covered by the protected areas. The most prominent biodiversity changes were observed in the upper freshwater Neva Bay, and moderate changes, in the lower brackish part of the estuary. Eutrophication, alien species and dredging activities are the major threats to biodiversity of the estuary. At present, alien species contribute about 8 per cent of species richness, however, 60-90 per cent of the biomass of bottom animals. Filamentous algae blooms affect biodiversity of zoobenthos in the shallow coastal zone. The climate-mediated fluctuations in near-bottom oxygen conditions are responsible for deterioration of zoobenthos in the open waters of the estuary. The decline of the benthic aboriginal crustaceans led to impairment of food conditions for fish and to a sharp reduction of their populations, which, in turn, was partly responsible for the population decline of ringed seals. Milder winters have also contributed to the decline in the numbers of this species. Dredging activities related to construction of new lands and ports are the main factor affecting fish, submerged macrophytes and waterfowl in Neva Bay. A considerable part of fish spawning grounds and waterfowl habitats in Neva Bay has been lost during the last decades. The long-term measures for conservation and improving of biodiversity should take into account periodicity of climatic changes and planned development of the region.

Behavior of blue mussels (Mytilus edulis L.) under the fluctuating environmental conditions

Bottom invertebrates of coastal waters live under the conditions of permanently fluctuating environmental factors. However, the relationship of these permanent (current) fluctuations with the functional activity of bottom animals has not been determined thus far. Most studies on their physiology and behavior of bottom invertebrates have been performed under relatively constant or forcedly varied, controlled laboratory con- ditions. These experiments have shown that artificial (usually considerable with respect to amplitude gradi- ents of water temperature and salinity cause significant changes in some parameters of the activity of bivalves (1-4). turbed) experiment methodology, i.e., without alter- ation of natural processes. The blue mussels were col- lected in the lower level of the intertidal zone of the bays Yarnyshnaya and Dal'nyaya Zelenetskaya and were kept in aquaria with a strong flow of unfiltered seawater that was supplied to the aquaria directly from Dal'nyaya Zelenetskaya Bay. The conditions in flow- through aquaria were essentially identical to the condi- tions of the upper subtidal zone, i.e., the level from which water was pumped in. The results of a special study on the corresponding of the conditions in the tanks to natural ones (6) showed that the difference between the experimental tanks and the natural envi- ronment with respect to the main seawater characteris- tics (temperature, salinity, phytoplankton, and seston) was insignificant in all seasons, and their fluctuations were correlated ( r varied from 0.88 to 0.97). The behavioral responses of adult blue mussels (30- 50 mm) were recorded by means of a mechanical acto- graph permanently during several months. The acto- grams (records of valve movements) were used to determine the following parameters of the mollusk behavior: SGS (percent of the maximum gapping of the shell valves during the period of the study), the fre- quency of contractions (adduction, ADD, number of contractions per day), and the amplitude of valve open- ing (AMP, percent of the maximum). SGS was selected as the main behavioral parameter (7). Ethological studies were performed from 1986 to 2003. Most data used in this study were obtained during the experiments performed in 1986-1991; however, they had not been treated and had remained unpub- lished until recent time.

Nutrient release and resuspension generated by ruffe (Gymnocephalus cernuus) and chironomids

Summary1. Benthivorous fish may play an important role in internal nutrient loading. Ruffe are highly specialised, feeding exclusively on bottom animals; thus all nutrients released via their feeding are derived from the bottom and are new to the water column. The fish can also release nutrients from the sediment through resuspension while searching for food.2. The aim of this study was to estimate experimentally in the laboratory the effect on water quality of resuspension and nutrient release by ruffe and bottom animals (chironomids).3. Ruffe released nutrients during 8 h experiments as follows: total P 1.4, dissolved PO4 0.6, total N 24.0 and NH4‐N 15.9 μg g−1 WW h−1. A decreasing trend in mass‐specific release was observed over time, probably because of starvation. The mass‐specific release of total N and NH4‐N decreased as the mean weight of fish increased. The mean ratio of excreted N : P was 32.4. In 26 h experiments with sediment and both ruffe and chironomids, ruffe increased nutrient concentrations and turbidity values significantly but chironomids had an effect only on turbidity. Neither ruffe nor chironomids affected the ratio of inorganic N : P concentrations. An interaction between ruffe and chironomids was found for turbidity.5. According to these results, benthivorous fish may increase nutrient concentrations in the water column and need to be taken into account when estimating internal loading.

Restoration of Some Parameters in the Development of Benthos After Reduction of Anthropogenous Loading in the Ecosystem of the Sevastopol Bay in the Black Sea

Research on benthic communities have been carried out in the Sevastopol Bay of the Black Sea for a hundred years. The anthropogenous influence began to have an effect already in the 20–30th. In this period, all oyster-banks were lost and the mussel-silt and mellina-silt communities have begun to degrade and were not found during almost seventy years in the Bay. The worst state of benthic communities was observed in the 60–90th, when species of bottom animals were not found over some parts of the sea. In this period, only 10 macrozoobenthic species were registered in the Bay. Mollusks: Nassarius reticulatus, Bittium reticulatum, Cerastoderma glaucum and polychaetes: Nephtys hombergii, Neanthes succinea have proved the most ‘enduring’ at high anthropogenous loadings The faunistic complex of benthic species registered in 1913 had the greatest similarity to the benthic species complex of 2002. Return of mussel, Melinna palmata polychaete and Ascidiella aspersa sea squirt in benthic communities of the Sevastopol Bay are responsible for the similarity between these faunistic complexes. The restoration of local populations of these benthic species has followed the significant decrease of the anthropogenous loading on the sea ecosystems as a result of the significant reduction of the military naval base in the Bay during the last five to ten years.