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A statistical analysis of the spatial distribution patterns of the macrozoobenthos in the streams and rivers of European Russia and Latvia (Oka, Don, and Gauja river basins) was carried out. Based on nonmetric multidimensional scaling (NMDS), the distribution of the macrozoobenthos in the study streams was shown to be continuous, with no distinct types of communities distinguished. Based on the ANOSIM method, statistically significant species complexes associated with substrate types, flow velocity, and size of the stream and main river basins were recognized. Using the SIMPER, characteristic and differentiating taxa at the generic or species level for each species complex were delimited, with the life-forms of these taxa evaluated. Although the taxonomic composition of species complexes of flowing waters is weakly predictable, a statistically significant clustering of taxon groups associated with key environmental factors has been found possible. Conducting such research in different hydrological types of water bodies in various geographical regions is a promising direction for the environmental monitoring of freshwater. [ABSTRACT FROM AUTHOR]

Abstract—The authors discuss the use of the Greenell concept of ecological niches to analyze the taxonomic structure of communities and their relationship with environmental factors. The modeling of ecological niches was carried out using the results of 30-year studies of macrozoobenthos communities on 90 small and 12 medium-sized plain rivers in the region of the Kuibyshev, Saratov, and Volgograd reservoirs. Geoclimatic indicators, relief characteristics, and hydrochemical assessments of the water quality at sampling points were considered as abiotic factors, where 11 variables with the least collinearity were selected. The multidimensional space of the initial abiotic factors was projected onto the orthogonal axes of the first two principal components; ordination diagrams with plotted points of the presence of species were constructed. The model of the potential ecological niche of each species was represented as an area in the space of latent variables, in which the habitat suitability index Z estimated by the probability density of occurrence corresponds to the given constraints. The authors used the Schoener and Hellinger indices to quantify the proportion of overlapping niches belonging to two different benthos taxa. The matrix of distances between overlapping niches was formed for all possible paired combinations of the 40 most ecologically significant macrozoobenthos species. Cluster analysis of the obtained distance matrix was carried out by the methods of hierarchical agglomeration and fuzzy k-means. In the general multidimensional space of abiotic variables of the region studied, four areas of collective niches for groups of species with maximum distances between their centroids were identified. The analysis of intergroup variation of environmental factors is given, and the characteristic features of each group are discussed: ecological strategy, biological traits, and tolerance level. [ABSTRACT FROM AUTHOR]

This paper presents results of comprehensive studies of saline rivers in the arid Elton Lake region based on hydrobiological surveys of planktonic and bottom communities. Two tables representing the species structure of communities and produced on the basis of survey data collected on 13 river sites in 2013 and 2018, including data on the abundance of hydrobionts belonging to 94 different taxonomic groups of macrozoobenthos, meiobenthos, and zooplankton, have been compared. The co-inertia analysis has identified a high statistical consistency of the data matrices determined by objective spatial distribution patterns of aquatic organisms. A randomization test was applied to the Procrustean correlation coefficient, and it showed that the conjugacy of the two species structures in the space of latent variables is statistically significant (p = 0.00026). Concurrently, a change trend was noted for the taxonomic composition of some surveyed communities affected by dynamic abiotic factors. The relationship between the taxonomic structure of hydrobionts and the combination of 30 abiotic environmental factors measured in the course of the hydrobiological and hydrochemical monitoring of the studied river sites was analyzed. Using canonical correlation analysis and the technique of projection to latent structures, a complex of ordination diagrams has been produced permitting the identification of specific "environmental niches" for each species group, including certain sets of biotope characteristics. A significant mutual correlation between the planktonic and bottom communities has been established. This correlation indicates close interrelations between these communities determined both by biotic interactions and by mutually consistent reactions to changes in aquatic environmental factors. [ABSTRACT FROM AUTHOR]

In this study, an attempt is made to evaluate the impact of environmental factors on the vertical distribution of the macrozoobenthos at the northeastern shelf of the Black Sea. The samples of macrozoobenthos were taken by an Ocean grab at the depths of 10–70 m in 2014–2017 along four transects between the Abrau Peninsula and the settlement of Shepsi. The particle size distributions of the bottom sediments and the near–bottom water temperature were also measured. Two major groups of stations were distinguished according to the quantitative structure and composition of the macrozoobenthos—shallow (10–40 m), corresponding to variable temperature conditions, and deep (50–70 m), corresponding to constant temperature conditions. Two subgroups were distinguished in the shallow zone coinciding with the upper mixed layer (10–15 m) and thermocline (20–40 m). The first subgroup was characterized by sandy sediments inhabited by the community of the suspension feeder bivalve, Chamelea gallina; silty sands at the stations of the second subgroup contained a community dominated by several Veneridae species. Silty sediments were spread all over the deep-water zone; the pelophylic bivalves Parvicardium simile and Modiolula phaseolina were dominant. The ratio of silt to sand fractions in the bottom sediments and the near-bottom water temperature were critical factors in distinguishing between the groups of stations. The subgroups were distinguished according to the percentage of aleurite and pebble. The coefficient of sediment sortedness, which reflects the stability of the hydrodynamics and the rates of sedimentation, also influences the differences (mostly due to Bivalvia). The total variation explained by depth almost overlapped with the variation accounted for by other factors. The major role in distinguishing between the groups belonged to the two taxa constituting most of the biomass (Bivalvia) and the density and species diversity (Polychaeta). [ABSTRACT FROM AUTHOR]

Communities of macrozoobenthos in the White Sea coastal water bodies that have partially or completely lost connection with the sea as a result of postglacial land uplift, are studied. As the degree of isolation from the sea increases, stable vertical stratification with a tendency to meromixis and gradual dilution of seawater provide the conditions for the formation of an unusual composition of macrofauna and succession, from a normal or slightly depleted marine biome to a completely freshwater ecosystem. Data collected in the years 2012–2017 present the macrozoobenthos community of five marine lagoons and four meromictic lakes in comparison with the marine communities of Kislaya Inlet, which connects the two water bodies studied, and with the freshwater lakes of the Kindo Peninsula. The typology of the water bodies was carried out according to the degree of isolation, taking into account the hydrological regime and differences in fauna lists. A naturally determined change in bottom communities occurs as the degree of isolation of the water body from the sea increases. In marine lagoons, regularly flooded by tides, there is a community of Macoma balthica (L. 1758)–Pontonema vulgare (Bastian 1865) Filipjev 1916, widespread in the marine littoral. In more isolated lagoon-type water bodies with a similar set of species, Mytilus edulis L. 1758 and Mya arenaria L. 1758 make up a significant share in biomass in addition to M. balthica. The populations of the gastropod mollusk Hydrobia ulvae (Pennant 1777) are much developed here. Even at this stage, the fauna comprises more littoral eurybionts (H. ulvae, M. balthica, M. arenaria, M. edulis, Arenicola marina (L. 1758), Tubificoides benedeni (d'Udekem 1855), chironomids, etc.) and less sublittoral stenohaline forms. At the next stage, H. ulvae dominates by biomass, and the share of the chironomid Chironomus gr. salinarius and oligochaete T. benedeni increases as well. Insects and their larvae (beetles, chironomids, and other dipterans) settle in shallow areas. In meromictic lakes, where a salt aerobic layer is preserved under the pycnocline, the fauna of the mixolimnion mainly comprises insect larvae, while only a few euryhaline forms remain from the marine fauna, namely, the amphipod Gammarus duebeni Lilljeborg 1852 and the chironomid Ch. gr. salinarius. At the stage of complete isolation from the sea, conditions are anaerobic below the pycnocline and, despite the suitable salinity, there is no marine fauna. In such water bodies, the benthos is represented exclusively by freshwater forms, mainly insects and mollusks. In completely freshwater bodies, chironomids make up the majority of the biomass; each lake has its own set of species, which changes from year to year. In the fresh water of Nizhnee Ershovskoe Lake, the population of G. duebeni remains in the part of the lake closest to the sea. The species diversity decreases as the water body is isolated from the sea; the maximum number of species was found in marine lagoons near Sonostrov Island (23–34 species); in Kislo-Sladkoe Lake, 10–15 species are found per survey. In Bol'shie Khruslomeny Lake, the aerobic part of the monimolimnion has a critical salinity and the species diversity is minimal (6–10 species). The number of species increases again after a stable fresh layer appears in the water body. The quantitative characteristics of the macrobenthos change in a similar way. The maximum abundance were noted in marine lagoons; in Kislo-Sladkoe Lake, the average abundance is significantly lower. In the meromictic water bodies with a fresh mixolimnion, the maxima of abundance and biomass are observed in the upper 0.5-m water layer, while in marine lagoons the maxima are located in the depth range of 1.0–2.5 m; in addition, in less isolated water bodies, the maximum biodiversity is observed in deeper layers than in more isolated ones. This layer is characterized by the highest content of dissolved oxygen, and often by supersaturation. The benthos abundance varies greatly in freshwater bodies. [ABSTRACT FROM AUTHOR]

Macrozoobenthic communities of Onega Bay of the White Sea were studied in 2010 at ten stations, which repeated the survey sites performed in the 1950s and 1980s by the staff of the White Sea Biological Station, USSR Academy of Sciences. Benthic communities where bivalve mollusks dominated by biomass were observed at all sites investigated in 2010. The stations were divided into two main groups; Modiolus modiolus was the dominant species in the first one, Clinocardium ciliatum in combination with various bivalve species as subdominants dominated in the second. There were also communities in which Hiatella arctica and Macoma calcarea dominated; each community was recorded at only one station. Due to the inability to follow accurately the sampling methods and the peculiarities of primary processing used in the historical surveys, the comparison of the data was carried out using only bivalves, because this was the most reliably defined group that unquestionably dominated in all communities. No significant changes were found in bivalve dominance. The replacement of the blue mussel settlement with a Hiatella arctica community was observed at a shallow depth (13 m). Deeper than 40 m, the dominants changed: Clinocardium ciliatum by Mya truncata (1952), Elliptica elliptica by Macoma calcarea (1981), and Clinocardium ciliatum by Macoma calcarea (2010); these changes were most likely associated with the patchy distribution of these key forms. Modiolus modiolus communities, observed in Onega Bay in 1952 and 1981 at depths of less than 40 m, were found in the same places in 2010. The stability of macrobenthic communities, where large, long-lived bivalves dominated (in particular, Modiolus), was most likely due to the absence of significant changes in the environmental conditions and of an anthropogenic load in Onega Bay during at least the second half of the XX century and the early XXI century. [ABSTRACT FROM AUTHOR]

The impact of climate change on the marine benthos has been widely discussed since the beginning of benthic surveys in the Barents Sea on a regular basis. Using historical data, this paper presents variations in the macrozoobenthos biomass in the eastern Barents Sea during four different climatic periods. Investigations have shown that the biomass of the macrozoobenthos in cold periods was lower than in warm times. The importance of stable climatic conditions for variations in the macrozoobenthos biomass is discussed as well. This paper provides examples of how some abundant species of the macrozoobenthos response to climate change. [ABSTRACT FROM AUTHOR]

Abstract—A comparative analysis of the variability of the species structure of macrozoobenthos communities in small and medium rivers of the Middle and Lower Volga river basin has been carried out. The statistically significant influence of the natural climatic zone, where the watercourse is located, and manifestation of the latitudinal gradient of biodiversity are shown. A list of indicator species has been made for each geographical zone identified using different criteria of biotopical distribution. Based on the analysis, the indicator value (IndVal) index, which takes into account the zonal distribution of both the occurrence frequencies of a species and its abundance ratios, was recognized as the most adequate. Association rules that contain combinations of species that most frequently occur together in hydrobiological tests have been formulated using the Apriory algorithm. [ABSTRACT FROM AUTHOR]

The seasonal variability of the macrozoobenthos in a saline lagoon characterized by the absence of a permanent connection with the sea is described according to the results of a survey in Ptich'e Lake (southern Sakhalin) in 2012-2013. Changes in the species composition, abundance, and biomass of the macrozoobenthos have been revealed. Features of the formation of species complexes, benthic communities, and trophic groups are shown. Causes of the phenomena described are discussed. [ABSTRACT FROM AUTHOR]

The present paper deals with the results of the first study (April and August, 2006-2007) of the taxonomic composition of macrozoobenthos in the highly mineralized Khara River. The study revealed 35 species and taxa of the rank above species. Data were obtained on the spatial distribution of the species composition dynamics and on the quantitative development of the macrozoobenthic community. The dependence of the structure of bottom communities on the parameters of the river's trophic status, biotopic diversity, and changes in hydrochemical parameters was determined. The environmental factors (total mineralization, ionic composition, pH, oxygen content, water temperature, overgrowth by macrophytes) influencing structural changes in macrozoobenthic community were determined. It is shown that diversity, number, and biomass of halotolerant macrozoobenthic communities increase with a rise in water mineralization from 6.9 to 14 mg/L. A new halophilic chironomid species of the family Chironominae, Tanytarsus kharaensis Zorina et Zinchenko, has been found. [ABSTRACT FROM AUTHOR]