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Ichthyofauna in the littoral zone the southern extremity of Lake Baikal was investigated. Modern data were obtained on fish composition in waters most affected by anthropogenic factors, where the probability of resultant changes in the fish community is highest. Long-term fish sampling was carried out in the zone of discharge and spread of wastes from Baikal Pulp and Paper Mill (BPPM); in regions near urban settlements; and near shore-protection construction operations. The data were compared with material previously collected, and with fish communities sampled in distant (control) areas. Variations in the composition of community are shown: some species that used to be absent were recorded in these areas, and possible reasons for their appearance are discussed. No distinct changes in the littoral fish were found attributable to anthropogenic influences. Recommendations on ichthyologic monitoring are proposed. [ABSTRACT FROM AUTHOR]

This paper reviews results of experimental and field studies of downstream migration of young fish carried out in the Institute of Ecology and Evolution (Russian Academy of Sciences) as a part of the research programme on fish behaviour and ecology. Studies of fish migrations have been dominated by descriptions of migratory routes and proximate control of orientation. Behaviour and ecological factors influencing variability of downstream migrations of fish larvae and fry are still poorly understood. Life cycles of most of freshwater fishes can be roughly considered as a sequence of “residential” and “migratory” phases. Migrating, or just moving between microhabitats, fish are especially vulnerable to various threats including impacts of water abstraction systems. Abiotic (water flow velocity, rheogradients, turbulence, visual habitat heterogeneity) and biotic (foraging conditions, predators, competitors and parasites) factors can cause changes in fish spatial distribution as well as shift from residential to migratory behaviour. From the viewpoint of fish protection, these changes are important not only in the vicinity of water abstraction sites, but also in more distant parts of the aquatic system that should be taken into account in long-term assessments of impacts of abstraction on fish populations in regulated rivers. Besides macro- and meso-scale impacts that affect fish migrations and spatial distribution, micro-scale habitat heterogeneity (hydrodynamic and visual) are important as factors triggering and controlling various aspects of young fish behaviour. Interactions of water abstraction zones with fish populations have to be analysed at ecological (meso-scale spatial overlapping and long-term dynamics) and behavioural (effects of micro-scale structures and events) levels. [ABSTRACT FROM AUTHOR]

In a first biomarker-based study in Lake Baikal, we demonstrated that the heat shock protein Hsp70, a biomarker of exposure, is present in various endemic sponge species of the lake. The expression of Hsp70 was induced following heat stress in tissue or dissociated cells of the Baikalian sponges, Baikalospongia intermedia, Lubomirskia fusifera, and Lubomirskia abietina. Increased Hsp70 levels were still visible after a recovery period of 24 h. Exposure of B. intermedia to lead (Pb) and zinc (Zn) caused a strong induction of Hsp70 in this sponge, while copper (Cu) was not effective. However, all these heavy metals were able to induce DNA damage, a biomarker of effect, in B. intermedia, as determined by Fast Micromethod. Induction of DNA damage in B. intermedia was also observed after exposure to the organochlorines tetrachloroguaiacol and pentachlorophenol, which are released by pulp bleaching. The Baikalsk Pulp and Paper Plant (BPPP) is considered to be one main potential source of pollution of the lake. Investigations of the influence of the waste water from the final refinement and aeration pond of BPPP revealed a concentration-dependent increase in Hsp70 expression in B. intermedia. In addition, the effluents of the pond were able to induce DNA damage. The basal level of DNA single-strand breaks/alkali-labile sites in B. intermedia collected close to the site where the BPPP effluents are discharged into the lake was higher than that in sponges collected at an unpolluted site. Our results suggest that Baikalian sponges are suitable bioindicators to monitor water quality and ecosystem health of the lake. [ABSTRACT FROM AUTHOR]

Two endemic Baikal species of oilfish, Comephorus dybowskii (“small golomyanka”) and Comephorou baicalensis (“big golomyanka”) live in the pelagic zone down to the bottom (1600 m). Both have numerous adaptations to the pelagic habitat. In this regard, the paper gives results of studies of blood under various natural conditions. The cell composition of peripheral blood does not differ between the species. Light and electron microscopy showed absence of granulation in polymorphic nuclear leukocytes. Significant differences in shape (number eccentricity) and sizes of mature erythrocytes were apparent. Parameters of red blood and cytometric indices do not change significantly within each species. However, high values of variation coefficient in the parameters of white blood were observed in both. Small golomyanka in comparison with big golomyanka have a higher percentage of erythroblasts, haemoglobin concentration and oxygen capacity of blood (OCB), while the percentage of polymorphic nuclear leukocytes and mature erythrocytes is less. Both species differ only insignificantly in number of erythrocytes, leukocytes, haemoglobin concentration in erythrocytes, index of leukocyte abundance, and thrombocytes per unit of blood volume. Small golomyanka caught at different depths do not differ much in most parameters of blood, but our analysis shows a high positive correlation between habitat depth, haemoglobin concentration and erythrocyte number per unit of blood volume. Blood characteristics indicate that small golomyanka is the more metabolically active species. [ABSTRACT FROM AUTHOR]

The paper presents an analysis and discussion on a phenomenon of Lake Baikal spring phytoplankton known as ‘melosira years,’ or high-productive years, which are years when spring a psychric set of planktonic algae intensively blooms in the interstitial water within the thawing ice and in the under-ice water. Alternative of these high- and low-productive years is one of greatest baikalian mysteries long attracting researchers’ attention. Analysis of a sequence of high-productive years from 1943 to present, allowed us to reveal 11- and 10-year cycles in long-term dynamics of the Lake Baikal spring phytoplankton. Within these basic cycles we have found enclosed three intervals between high-productive years. Moreover, these intervals being usually 3 and 4 years long became doubled, i.e., 6 and 8 years long, from 1968 to 1990 that equals 22 years in length, or two 11-year fragments. This phenomenon of doubling can be explained in terms of the resonance theory so we consider the ‘melosira years’ phenomenon to be bound up with solar activity, resonantly influencing baikalian phytoplankton. Also we found that Lake Baikal spring phytoplankton skip between their 11- and 10-year cycles in conforming to a current solar activity length. [ABSTRACT FROM AUTHOR]

The lakes of mining and metallurgical regions are modified not only by climate warming, but also by diverse human impacts. The primary hypothesis of this study was that the response of lakes in the Ural metallurgical region to global warming and human land use was mediated by loading of potentially toxic elements (PTEs) and acidification. To test this hypothesis, we carried out a diatom and geochemical analysis of sediments accumulated through the past 800–1200 years and a hydrochemical analysis of four lakes. All lakes were characterized by shifts in diatom assemblages and changes in diatom indices and planktonic diatoms in the nineteenth and the twentieth centuries. Despite contamination by PTEs, lakes Turgoyak, Tavatui, and Syrytkul experienced an increase in trophic state and in planktonic diatoms. Oligotrophication was inferred only in the record of Lake Ufimskoe which was most contaminated by PTEs, but marked by the least other human impact. We conclude that diatom assemblages in the Middle and Southern Urals lakes primarily reflect the influence of local human activity, rather than the global warming. Industry-related acidification and higher PTEs altered lake development only under the condition of weak influence of other human activities. [ABSTRACT FROM AUTHOR]

Knowledge of factors affecting the diversity of benthic invertebrates is very important for biodiversity conservation, for monitoring, restoring and maintaining aquatic ecosystems. The purpose of this study was to investigate how the diversity and distribution of freshwater mollusks related to environmental factors. Twelve species of freshwater mollusks were identified during a survey of 15 thermokarst lakes in the Gydan Peninsula, Russia. Canonical correspondence analysis (CCA) was used to study the relationships between environmental variables and species abundance. The first CCA axis correlated with the content of macro-ions, mainly Mg2+, Na+, Cl−, substrate types, and plant remnants. Along the second CCA axis stations were ordered by depth and the presence of mosses. We found that the type of substrate, depth, abundance of mosses and hydrochemical parameters play an important role in the distribution of the mollusks in thermokarst lakes. These results expand our understanding of mollusks ecology in thermokarst lakes, and identify environmental stressors important for the performance of abiotic control. [ABSTRACT FROM AUTHOR]

The anaerobic microbial community in deep-water sediments of Lake Baikal is mainly methanogenic. Organic matter utilization as a result of methane production exceeds that resulting from sulfate reduction. The study of microbial activity in sediments of regions of hydrothermal venting and gas hydrates shows similarities with hydrothermal oceanic regions, and indicates an important role of methanogenic and methanotropic communities in the carbon cycle of these regions of Baikal. [ABSTRACT FROM AUTHOR]

Small lakes of the boreal zone are highly sensitive indicators of both global environmental change and local anthropogenic pressure. This work presents the results of multidisciplinary study of three small, seasonally stratified lakes of NW Russia, conducted since 2002 to the present time. These lakes were subjected to various degree of impact by rural population and agricultural activity since the beginning of twentieth century but the population and anthropogenic pressure have decreased since 1990s. To monitor the recovering of these lakes from human impact and to relate the evolution of their hydrochemical parameters to short-term weather events and global climatic trend, we measured the lake water temperature and chemical composition (carbon, macro- and micronutrients, trace elements) in summer and winter over full depth of the water column. The pH and concentration of DIC, SO4 and H2S decreased over past decade. Concentrations of Si and nitrite increased over past 15 years, probably linked to progressive replacement of diatoms by cyanobacteria. We also recorded an increase in concentration of Cl and major cations in all lakes, likely linked to increasing connection to groundwater reservoirs. Some trace elements (Fe, Mn, Al, Zn, As, Pb) can serve as suitable indicators of on-going natural processes controlling lake response to external factors. Unlike widely reported global trend of DOC and Fe concentration increase in boreal surface waters of Europe and Northern America, such trend was not discernable in studied Fe-rich humic lakes. We conclude on the necessity of complex, multidisciplinary studies of small humic lakes in the boreal zone, because these "model" lakes can serve as important proxies of on-going environmental changes in highly abundant aquatic ecosystems of poorly characterized regions of NW Russia. [ABSTRACT FROM AUTHOR]

The aim of present research is to study the patterns of phyto- and zooplankton fluctuations in endorheic soda lakes (Uldz Gol-Torey Basin, southeastern Transbaikalia, Russia) under arid conditions because studied area is becoming increasingly arid. Plankton samples were collected in summer during time intervals with different lake water levels using standard hydrobiological methods. We detected four patterns of change in plankton communities with changing environmental conditions (increasing total dissolved solid, pH and temperature, and decreasing depth). The first pattern is characterized by a predominance of green algae, charophytes, diatoms and euglenophytes; the species composition and dominant zooplankton assemblage are the same in different years. The second pattern is characterized by a loss of cryptophyte and chrysophyte algae, a dominance of green and blue-green algae, a decrease in zooplankton species diversity, and an increased abundance of zooplankton, the dominant species are consistent over time. The third pattern exhibits marked decreases in phytoplankton diversity and density, a dominance of green algae and diatoms, a further decrease in the species richness of zooplankton, and increased abundance and biomass of some species. The fourth pattern is a marked by a reduction in plankton species diversity to a monospecific community. [ABSTRACT FROM AUTHOR]

The divergence of reproductive strategies is an important development toward intraspecific diversification. We describe contrasting spawning patterns of parapatric and sympatric Arctic charr forms in two interconnected lakes Kiryalta-3 and Kiryalta-4 in Transbaikalia for comparison to charr reproduction in nine more lakes of this region. In each Kiryalta lake, two charr forms (small and large) differing in growth and diet are present, in Kiryalta-3 they are morphologically more distinct than in Kiryalta-4. In Kiryalta-3, the spawning of the small form was recorded in autumn and spring suggesting two subpopulations; spawning time of the large form is unknown. In Kiryalta-4, both forms spawn in autumn. Overall, reproductive patterns of Transbaikalian charr vary greatly in spawning time, duration, location, depth, and bottom substrate. Different populations and sympatric forms spawn in early or late autumn, spring, summer, or during more than one season, including the littoral or profundal zone, over rocks or silt, and from 1–2 weeks to at least 7 months. Peak spawning time difference between sympatric forms can reach up to 5 months, and is correlated with morphological and genetic differences. Diversification of reproductive strategies largely contributed to the emergence of exceptionally high diversity of Transbaikalian charr. [ABSTRACT FROM AUTHOR]

The values of pH in the digestive tracts of 20 freshwater fish species inhabiting various Russian Federation waterbodies were studied. Only in six species ( Coregonus lavaretus, Coregonus migratorius, Catostomus catostomus, Carassius gibelio, Rutilus rutilus, Leuciscus leuciscus) out of 20 species, the differences in pH values between different regions of the intestine were significant. Feeding habits, feeding frequency, and gut fullness in fish affected pH values. Temperature was one of the most important factors affecting pH values. During cold seasons (spring and fall; average water temperature: 8-10 and 5-6C, respectively), the pH values in fish guts were higher than that in the summer seasons(water temperature 22-25°C) for C. gibelio, Perca fluviatilis, Cyprinus carpio, L. leuciscus, and R. rutilus from the Chany Lake. Similar results (lower pH values in intestine at higher water temperatures) were also obtained for C. gibelio in warmer years in comparison to colder years in the same waterbody and in L. leuciscus and P. fluviatilis in the different waterbodies with different water temperatures. It is hypothesized that dependence of pH in fish gut on temperature may serve as a regulatory mechanism for maintaining the activities of hydrolytic enzymes at the required level for their successful functioning. [ABSTRACT FROM AUTHOR]

Chemical and biological components of the Selenga River waters, the largest tributary of Lake Baikal, differ significantly from the lake waters. Active transformation processes of river waters into the lake ones occur in the vast barrier-like zone in the river-sea boundary areas. This study presents results on the spatial distribution and dynamics of water chemistry as well as the quantity and diversity of phyto- and bacterioplankton at a distance of 14 km off the Selenga River mouth. The most representative tracers of river and lake waters are total amount of ions and sulphates. Principal changes of chemical and biological parameters were fixed at 1-3 km off the Selenga River mouth that was determined as a mixing zone. Intense development of phytoplankton and eukaryotic picoplankton causing the decrease of nitrate and phosphate concentrations and organic matter rise were registered in this area. Gradual replacement of river phytoplankton by the lake one, abundance reduction of microorganisms and organotrophic bacteria and percentage increase of oligotrophic and psychrotolerant bacteria occurred in the mixing zone. Replacement of PC-rich picocyanobacteria by PE-rich ones was also recorded here. At a distance of 5-7 km off the shore, nutrient concentration and plankton composition were similar to those of Lake Baikal. [ABSTRACT FROM AUTHOR]

Ancient lakes are excellent laboratories for evolutionary research, where species can be studied in the cradle where they originated. In this article, we investigate two endemic ostracod species flocks from the two oldest lakes in the world, Lake Baikal (LB) (ca. 28 myr) and Lake Tanganyika (LT) (ca. 12 myr), with DNA sequence data. Nuclear ITS1 failed to resolve the phylogeny of both flocks. Whilst most phylogenetic relationships of the Tanganyika flock are resolved with mitochondrial COI, the Baikalian tree contains multifurications of up to seven different clades. The Tanganyikan Cyprideis flock shows higher genetic variability, which matches its higher morphological variability. A significant deviation from a constant divergence rate through time indicates that the Cytherissa flock most likely experienced explosive speciation events during its earlier history. Comparative analyses of substitution rates furthermore revealed that they are not clock-wise for COI. Ancestral Cytherissa probably radiated in LB 5-8 myr ago, around the time when the cold, oxygenated abyss was formed in LB. The Tanganyikan Cyprideis flock is almost twice as old as the Baikalian Cytherissa flock, and possibly older than LT itself, ca. 15 myr. The Cyprideis flock has survived drastic lake level changes and resulting salinity crises during its entire history. [ABSTRACT FROM AUTHOR]

Taxonomical and geochemical investigations on freshwater ostracods from 15 waters in Central and Northeast (NE) Yakutia have been undertaken in order to estimate their potential usefulness in palaeoenvironmental reconstructions based on regional fossil records. Higher variability in environmental factors such as pH, electrical conductivity, and ionic content was observed in thermokarst-affected lakes in Central Yakutia than in NE Yakutia lakes. Species diversity of freshwater ostracods reached up to eight taxa per lake, mostly dominated by Candona weltneri Hartwig 1899, in Central Yakutia, whereas in NE Yakutian waters the diversity was lower and Candona muelleri jakutica Pietrzeniuk 1977 or Fabaeformiscandona inaequivalvis (Sars 1898) had highest frequencies. Coupled analyses of stable isotopes (δ18O, δ13C) and element ratios (Sr/Ca, Mg/Ca) were performed on both host waters and ostracod calcite, aiming to estimate the modern relationships. Correlations between host waters and ostracod calcite of single species were found for δ18O, δ13C and Sr/Ca and Mg/Ca ratios. The relationships between δ18O, Mg/Ca and Sr/Ca ratios and electrical conductivity (salinity) as an expression of solute concentrations in the waters mainly controlled by evaporation are more complicated but evident, and may be useful in future interpretation of geochemical data from fossil Siberian ostracods. [ABSTRACT FROM AUTHOR]

Data on Secchi disk transparency in Lake Ladoga, the largest lake in Europe, collected between 1905 and 2003, were used to detect climatic (interannual) trends for lake regions with various depths. The seasonal variations in Secchi depth ( D s) during the ice-free period both for limnetic regions with large differences in bathymetric characteristics and for the whole lake were estimated by more than 7000 transparency measurements. The two-dimensional data sets have a spatial resolution of approximately 20 km and are geo-referenced by latitude and longitude in Lake Ladoga. Monthly mean spatial transparency distributions and their variances were calculated from May to October. The spatial distributions of the transparency for each month are discussed within the context of lake bathymetric patterns. The maximum values of Secchi depth (more than 4 m) occur during May and October in deep regions. Both the minimum mean value of water transparency and minimum horizontal gradients of D s for the lake occur in August. The regions with significant interannual (climatic) decreasing trends of D s have been identified. These areas increase in summertime and cover approximately half the lake area. In spring and autumn the areas decrease and occur in the southern near-shore regions. The mean downward climatic trend of water transparency in Lake Ladoga is 0.02 m/year. [ABSTRACT FROM AUTHOR]

Since the middle of the 20th century, six species of Ponto-Caspian amphipods ( Chaetogammarus ischnus, C. warpachowskyi, Chelicorophium curvispinum, Dikerogammarus haemobaphes, Obesogammarus crassus, Pontogammarus robustoides), one Baikalian amphipod Gmelinoides fasciatus and one amphipod of Atlantic origin Gammarus tigrinus have expanded in Russia and adjacent regions. A wide variety of human mediated vectors such as deliberate and accidental introductions, natural migration via constructed inland waterways and high rates of spread, survival and reproduction in these species have facilitated rapid dispersal and successful establishment of these alien species. Causes of successful establishment of these invaders and potential consequences of the invasions including extinctions of native species in rivers, lakes and estuaries of north-western Russia are discussed. [ABSTRACT FROM AUTHOR]

Relationships among salinity and diversity, abundance, biomass of major biological components of Chany Lake (western Siberia, Russia) are examined across a salinity gradient. As salinity increased from 0.8 to 6.4 g l−1, the species richness of aquatic vascular plants decreased from 16 to 2 species, of phytoplankton from 98 to 52 species, and of zooplankton from 61 to 16 species, but changes in species diversity of zoobenthos were negligible. [ABSTRACT FROM AUTHOR]

The influence of salinity on 27 Artemia parthenogenetica populations in Siberia was investigated. Salinity in the lakes sampled ranged from 50 g l−1 to 265 g l−1. Artemia were characterized on the basis of biomass, number of cysts, weight and the length of females, number of cysts in brood and several biometric parameters. Average values of shrimp biomass, number of planktonic and benthic cysts and number of cysts in broods were largest in locales with salinity 77–144 g l−1. Increased salinity reduced the number of setae on the furcal branch and the length of the cephalothorax. [ABSTRACT FROM AUTHOR]

Phenology and evolution of a common endemic caddisfly species Baicalina bellicosa Mart. was studied during 2000–2002. Benthos samples were taken monthly, by diving, from stones at depths of 3–4 m at a station near Berezovy Cape. Simultaneous observations were made on the growth and development of caddisflies kept in refrigerators at temperatures close to Lake Baikal. Dimensions of over 800 larval specimens of B. bellicosa were analyzed during a year, not less than 45 per month. We defined the period of imago flight, egg laying, larval emergence from the egg and its post-embryonal development. Life span is estimated to be not less than 2 years. [ABSTRACT FROM AUTHOR]

An estimate of the role of endemic diatom algae of Lake Baikal, their contribution to numerical abundance and to biomass, was obtained on the basis of long-term monitoring in the pelagic zone, and in shallow water bays and near the mouths of rivers. Endemic diatoms are distributed over a major part of the lake, except for shallow-water bays. During a major part of the year, they dominate in biomass and in numerical abundance, making a major contribution to the rate of accumulation of modern sediments. [ABSTRACT FROM AUTHOR]

Based on the detailed temporal scale of climatic events in the Northern Hemisphere from late glaciations to Holocene, and data on variability of CO2 concentrations in the atmosphere, some abiotic indices of the ecosystem of Lake Baikal during the past 16 thousand years is reconstructed. In the Late Pleistocene, extremely low input of nutrients from the drainage area corresponded to inclement ice-thermal conditions and this resulted in an extremely low concentration of diatom algae frustules in Baikal bottom sediments. At 11–9 thousand years B.P., greater heat and moisture supply, deglaciation, enlarging of adjacent vegetated areas, and increase in weathering rate of silicon and phosphorus bearing minerals, caused the input of nutrients to the water column of Lake Baikal to substantially increase. It is likely that these circumstances, as well as improvement of physical conditions favorable for the growth of diatoms (increase of under-ice radiation, decrease of the layer of convective mixing, etc.) created the conditions for sharp intensification of diatom development in Lake Baikal eight thousand years ago. [ABSTRACT FROM AUTHOR]

Studies on the linear size variations, onthogenetic changes of the taxonomically important features (eye number, body coloration) and the inside cocoon life span of the endemic planarian Baikalobia guttata (Gerstfeldt, 1858), the mass species of shallow-water stony littoral zone of Lake Baikal have been carried out. Growth curves based on weekly 3.5 months long in vitro measurements and observations of juveniles, hatched from 15 cocoons, have been constructed and tentative life span of B. guttata has been evaluated. The dependence of the number of juvenile specimens and their body length on the cocoon size is determined. [ABSTRACT FROM AUTHOR]

In relict Lakes Baikal, Biwa and Khubsugul three orders: Hydrida, Athecata and Limnomedusa (?) of the class Hydrozoa were found. In Lake Baikal, only representatives of Hydrida, such as Pelmathohydra baikalensis (endemic of Lake Baikal), P. oligactis and Hydra circumcincta were found (the last two species had not been found there before. Recent studies of the phylum Cnidaria in Lake Biwa showed the presence of Pelmatohydra oligactis and a representative of the family Clavidae which has been treated as a new species, Pachycordyle kubotai. In Lake Khubsugul a single representative of Hydrida has been found so far which is suggested to represent a new species of Pelmatohydra. According to techniques described earlier air-dried chromosome slides were prepared. The karyotype of P. kubotai were studied using conventional chromosome staining (by 6–10% Giemsa in the Sørensen’s buffer, pH 6.8), whereas karyotype of P. baikalensis was studied using conventional and C-banding techniques. C-banding to reveal highly repeated DNA followed the protocol by Sumner (1972). [ABSTRACT FROM AUTHOR]

Large bivalves represented in Lake Baikal by anodontines of the genus Colletopterum Bgt. are revised on the basis of a morphological examination of specimens preserved in Zoological Institute RAS, St. Petersburg (ZISP) and in Institute of Biology and Soil Science Far east Branch RAS, Vladivostok (IBSS). Shell shape, shape of valves, curvature of the frontal section of the valves, location of umbones and the ratio of shell width to height at the ligament were all taken into consideration. Results indicate that Lake Baikal is inhabited by five species of Colletopterum instead of only the formerly known subspecies C. ponderosum sedakovi (Siemaschko), which we regard as a synonym of C. anatinum (L.) following reidentification of the lectotype of the former. Three European–Siberian species: C. anatinum, C. piscinale (Nilsson), and C. nilssonii (Kuester), are recorded from the Baikal drainage for the first time.Specimens of large Baikalian bivalves in the ZISP collection bearing subspecies names by W. Dybowski are recognized as a mixture of different species. All type specimens were examined to establish their identity. It is concluded that C. sorensianum (W. Dybowski in B. Dybowski, 1913) (syn.: Anodonta complanata sorensiana W. Dybowski in B. Dybowski, 1913; A. cellensis sorensis W. Dybowski erroneous spelling by Shadin, 1938; A. cellensis ssorensis W. Dybowski erroneous spelling by Shadin, 1952) is a valid species characterized by having the flattest shell. Other subspecies names proposed by W. Dybowski’s are regarded as junior synonyms of Siberian–European species: C. piscinale (Nilsson, 1822) (syn.: A. cellensis selengensis W. Dybowski in B. Dybowski, 1913; A. nova W. Dybowski, 1913), C. anatinum (L., 1758) (syn.: A. sedakovi Siemaschko, 1848); A. piscinalis sorica W. Dybowski in B. Dybowski, 1913); C. ponderosum (Pfieffer, 1825); C.nilssonii (Kuester, 1842).The key to identification of Baikalian large bivalves are also provided. [ABSTRACT FROM AUTHOR]

The current list of planktonic ciliates dwelling in Lake Baikal numbers 102 species, 81 of which are considered as euplanktonic. This plankton ciliate community is characterised by high percentages of oligotrichs and gymnostomes, 28 and 27%, respectively. One third of these ciliates are cold-stenothermic species, with temperature optimum preference of 0–4 °C, including all the species believed endemic. They develop only in under-ice plankton though remaining present in the water column until June–July. The other two thirds of planktonic ciliates are eurythermic and widespread in lakes of the Northern Hemisphere or cosmopolitan. Two maxima occur annually in baikalian planktonic ciliates: the first in March–April and the other in August–September. They coincide with the annual maximal development of phytoplankton. During years of low to middle-level primary production, the summer maximum of protozooplankton has been higher than the spring one. But the latter can exceed the former in years of high primary production. Mean biomass of ciliates (in 0–50 m) reaches 140–500 mg m−3 during maximum abundance, decreasing by 5–10 times in the rest of the year. Mixotrophic ciliates contribute up to 6% of the under-ice pelagic ciliate community but sharply increase to 80–90% in summer, augmenting the autotrophic plankton biomass by 30–40%. In the last decade, pelagic ciliates have seldom exceeded 4–5 thousand cells l−1 at maximum development, averaging 1–2 thousand cells l−1. The dominant role of nanooligitrichs and high percentage of mixotrophic ciliates are characteristic of summer plankton of Baikal. Planktonic ciliates in interstitial water of melting ice also make a significant contribution to total abundance. Their rapid increase in population, which can exceed 10 thousand cells l−1, is another peculiarity. It is thought that inter-annual dynamics of the ciliates are related with long-term cycles of baikalian phytoplankton. [ABSTRACT FROM AUTHOR]

Our karyological investigations provided and certain peculiarities in the ecology of different planarian species of Bdellocephala genus support the definition of B. melanocinerea and B. roseocula as individual species. We also suggest restoring the species status of B. agrillosa described first by Korotneff (1912) and later made a synonym of B. a. angarensis (Porfirieva 1979). B. baicalensis baicalensis and B. baicalensis subniger suggested as subspecies by Porfirieva (1979) are considered as geographical races by us; no distinctive features between them, except colour intensity variations in the representatives of this species from different regions of Baikal, were observed; their karyotypes are identical. B. a. angarensis and B. a. olivacea are proposed B. angarensis subspecies. We have assumed that B. baicalensis (2 n = 20), which is distant from all other Baikalian Bdellocephala would have originated from an ancestor common to a Eurasian species, B. punctata, with the smallest chromosome number (2 n = 16). The remaining Baikal species are closer to the Japanese B. annandalei and B. brunnea and the Far-East B. grubiiformis with 2 n = 28 by the karyotype characteristics (2 n = 24, 2 n = 26). [ABSTRACT FROM AUTHOR]

An electron-microscopy study of Aulacoseira baicalensis, A. islandica ( A. skvortzowii), Cyclotella baicalensis, C. minuta, and Stephanodiscus meyerii in phytoplankton samples from some mountain lakes of Zabaikalye (an area north and east of Lake Baikal) shows that these algae possess morphological similarities with the algae inhabiting Lake Baikal, including some elements of their ultra-structure. We hypothesise that they were more widespread in the past and persist today in mountain lakes along the Baikal rift zone owing to certain features of their biology. We conclude that these baikalian diatom algae, previously regarded as endemic, should be re-assigned to relict status. [ABSTRACT FROM AUTHOR]

A comparative analysis of structure–functional parameters of microbial communities in estuaries of Lake Khubsugul rivers has shown that the level of development of the total number of microorganisms (TNM) is 2.5 times lower than in analogous places in Lake Baikal. Waters of Baikal rivers were, on average, 1.7 times richer in saprophyte bacteria than the Khubsugul river waters. Bacterial production in rivers and their estuaries in Baikal averaged over twice those of Khubsugul. Trophic levels in rivers and estuaries Khubsugul was lower than in Baikal. Structure–functional indices in the estuaries Baikal and Khubsugul rivers are at levels typical of oligotrophic and ultra-oligotrophic waterbodies. Microbial production in bottom sediments of Khubsugul is comparable, in absolute terms, with productivity characteristics of microbioceonoses in Baikal. Conditions governing the bioproductivity of bacterial populations are relatively more homogeneous in the Khubsugul benthic. The functional activity of microbioceonoses in bottom sediments of the lakes studied, determined by 14C-assimilation, dehydrogenase and cellulose activity, depends on lithological and granulometric composition of bottom sediments. Activity increases in the sequence: sands – sandy silts – clay silts – silted sands – detritus silts, reaching maximum in (15 mkg production ( P), 444 mkl H2 dehydrogenase activity (DA) and 625 mkg glucose cellulose activity (CA)). Fermentative activities of productivity and metabolism of bottom microbiocoenoses in these two lakes are characterized by closeness of values of energy and matter exchange at levels typical of oligotrophic and ultra-oligotrophic water ecosystems. [ABSTRACT FROM AUTHOR]

In Lake Baikal, frontal zones are a factor forming the pelagic structure, including area limits of pelagic communities. The spacial distribution of Baikal micro-organisms and diatom algae is known to be influenced by the vertical circulation of Lake Baikal deep waters during the spring thermal bar. In June 2001, we studied the distribution of plankton invertebrates and ways in which it depends on physico-chemical and biological parameters of water in the vicinity of spring thermal bars. Samples were taken through June 11–13th along three transects, across the middle basin of Lake Baikal and the Selenga shallow waters, namely at the Boldakovo River, Cape Sukhinskiy and the Kukuy branches of the Selenga River. As a consequence of the lake possibly being warmed later than usual, and compare with a previous study in 1993, the upper layers with temperatures close to 4 °C, were located near the shore where water depth was 14–100 m, from north to south. The littoral waters, warmed above 4 °C and reaching 12.7 °C near Cape Sukhinskiy, are known to differ from the open lake in hydrochemical indexes, raised number of bacterioplankton and the structure of algae coenoses (in particular, the presence of algae which indicate the spread of the Selenga River waters). An unusual vertical distribution of autotrophic picoplankton in terms of raised concentrations at the bottom, 60 m deep, occurred at the Cape Sukhinskiy transect within a thermal bar zone. This indicated the descent of upper waters rich in picoplankton. The zooplankton structure in the littoral also differed from that in more open waters where temperatures were below 4 °C, mainly by its richer diversity increased by littoral inhabitants. The pelagic amphipod Macrohectopus branickii preferred cold waters less than 4 °C. Crustaceans and rotifers were separated into different groups according to spacial distribution. [ABSTRACT FROM AUTHOR]

Investigations of Baikalian phytoplankton in 1960s showed that some very small blue-green algae with a cell diameter of 1.5 μm develop in great abundance in Lake Baikal in summer. They were described as a new endemic species – Synechocystis limnetica Popovsk. S. limnetica was found as mass dominant species of the autotrophic picoplankton. Knowledge on species composition of Baikalian picoplankton is limited to this species. Autotrophic picoplankton (APP) communities were studied monthly from 1997 to 2001 at the monitoring station in southern Lake Baikal. Microscopic examinations of picoplanktonic samples based on the fluorescence of pigments, cell morphology and ultrastructure revealed that Lake Baikal АРР is dominated by chroococcoid phycoerythrin-rich cyanobacteria of genus Synechococcus. Cyanobacteria of this genus were represented by various morphotypes throughout the study: coccoid and ellipsoid Synechococcus spp. 0.85 × 1.1 μm by size, constituting the main mass of autotrophic picoplankton, their proportion varying during the year from 74 to 97%; Synechococcus-species with short and long rod-shaped form of cells, reach maximum (8–18%) in the autumnal period. Endemic species of Lake Baikal – S. limnetica contribute 1–4% in APP communities. Baikalian APP was found to include free aggregated cells of Synechocystis- and Synechococcus-type, to 5% in autumn, as well as the colonial species Aphanothece clathrata f. brevis, the contribution of which to total autotrophic picoplankton fraction changes significantly in seasonal and annual aspects. Picoplanktonic green algae are not especially abundant in Lake Baikal, and, on average did not exceed 8% of the total APP. The sizes of picoalgae are 1.25 × 1.75 μm, both single cells of green algae; aggregated forms are noted in the picoplankton. Maximal abundance of autotrophic picoplankton was registered in a near-surface layer in late July (7.36 × 105 cells ml−1), and the minimum number (2.03 × 104 cells ml−1) in May, during the period of spring isothermal mixing. [ABSTRACT FROM AUTHOR]

The region between the Oka and Volga rivers has been largely neglected with respect to tardigrade biodiversity. In the present study a total of 21 species from 7 genera, 3 families, 2 orders and only 1 class of tardigrades were present, and some of their ecological preferences were noted. The tardigrades in the studied region were mainly cosmopolitan. Eurytopic, hygrophilic and xerophilic species were common while obligate freshwater species were not found. There is a marked similarity in the tardigrade fauna within similar habitats from different locations within the region. [ABSTRACT FROM AUTHOR]

Species composition and distribution of macrozoobenthos have been studied in the shallow water zone (0–20 m) of Southern Lake Baikal (Bolshiye Koty Bay). The amount of taxa recorded reached up to 244 species distributed among 16 distinctive communities of complex structure and high species diversity. The Shannon index of specific diversity was found to vary between 2.9 and 4.8 bits. Mosaic spatial distribution of communities is controlled by both biotic and abiotic factors. Trophic zones with respect to the bottom-dwellers are determined by two lithodynamic phenomena: washout and accumulation of thin deposits (fine to medium silt and mud). The bottom with coarse clastic material (pebbles and boulders), where fine sediments are eroded and resuspended, is dominated by immobile and mobile sestonophagous species as well as by the communities dominated by detrito- and phytophagous species. Areas with soft fine sediments are dominated by macro-invertebrates, which ingest the substrate indiscriminately. [ABSTRACT FROM AUTHOR]

In and around the endemic-dominated Lake Baikal, palaearctic species are generally restricted to shallow, sheltered bays and in- and out-flowing river floodplains. However, we observed populations of the palaearctic snail Lymnaea (Radix) auricularia on the steep, rocky littoral of Lake Baikal proper. We compared the morphology of 542 shells sampled from this new habitat with potential source populations from conventional habitats. A size-free Discriminant Analysis indicated a strong morphological differentiation of the newly established populations from their likely sources. The new populations had a more compact shell shape with a wide aperture, which may be advantageous in wave-exposed habitats where a firm attachment to the substrate is needed. Shells from the conventional habitats were more elongated, with a narrow aperture, which may be advantageous in habitats that have a dry period where retreating into the mud is required and water loss should be limited. These results may suggest that selection is acting on shell shape in Lake Baikal. The apparent recent arrival of this pandemic gastropod in a habitat previously dominated by endemics constitutes a potential ecological threat and an alert to possible ecological change. [ABSTRACT FROM AUTHOR]

A new species of Haplostomella Chatton & Harant, 1924, H. borealis n. sp., is described from two ascidian hosts taken in the White Sea. This species is most readily distinguished from its congeners by the structure of the mandible which comprises a strong tapering gnathobase and a vestigial palp. Supplementary descriptive notes are provided on Haplostomella distincta Ooishi & Illg, 1977, based on new material discovered on the opposite side of the Bering Strait from the original material. Minor geographical variation is exhibited by this species. A new species of the genus Haplostomides Chatton & Harant, 1924, H. sanamyani n. sp., is also described, based on material collected in the Bering Sea. A key to species is provided to facilitate the identification of the nine species recognised in this genus. [ABSTRACT FROM AUTHOR]

The mining company Karelian Pellet in NW Russia extracts iron ore and processes it locally into iron pellets. The production operations have effects on the environment in the form of air pollution (SO2 and dust) and waste water emissions. The waste waters from the process and the mining pits are let out into a dammed basin, formerly the natural Lake Kostomuksha. This basin flows north-east through several small lakes (e.g., Poppalijärvi, Kento) to the larger lake Middle Kuito and the White Sea. For these small lakes an exceptionally high mineral content, high pH value, and high concentrations of potassium, lithium and nitrogen in the water have been characteristic. However, the total phosphorus content (6–9 μg l-1) is slightly lower than in the Lake Upper Kuito (11–13 μg l-1) which acts as a reference lake. Biota from bacteria to fish were quantitatively sampled in August 2000 and 2001. Our results suggest a twice higher biomass of both phytoplankton (mainly picoalgae) and fish (biomass per unit effort) in the lakes downstream from the mine in comparison to the reference lake. Zooplankton and zoobenthos biomass both peak in L. Kento, the lake in the middle of the outflow series. The fish fauna (seven to eight species caught) is the same in all lakes and is dominated by perch and roach. Both grow well and roach show best growth in L. Poppalijärvi, next to the waste basin. Perch gills show some histopathological changes which do not, however, appear to affect either growth or reproduction. [ABSTRACT FROM AUTHOR]

Studies an amphipoda Echiuropus bekmanae from Lake Baikal in Russia. Number of amphipoda species found in the lake; Device that collected Echiuropus bekmanae.

Focuses on oligochaete species-related studies conducted in abyssal zone of Lake Baikal in Siberia, Russia. Characteristics of the lake; Evaluation of factors likely to affect oligochaete abundance with depth and in sediment; Effect of abyssal area of the lake on origin of oligochaete taxonomy.

Examines the carbon content of some freshwater rotifers in Russia. Identification of the species; Determination of high temperature combustion method of Salonen; Collection of carbon analysis from different water bodies.

Explores the pattern of recovery of disturbed microbial communities inhabiting hard substrates in the White Sea, in Saint Petersburg and in Karelija, Russia. Factors contributing to the recovery of the communities; Characteristics of the microbial communities in the field; Abundance of detritus in climax microfouling communities in White Sea.

Investigates the algal flora and invertebrate fauna of Lake Cheder in Russia. Biodiversity of the lake; Detection of bromine and boron in mud; Characteristics of salt water bodies.

Focuses on specimens of the bdellocephala angarensis bathyallis timoshkin ∧ porfirjeva species that have been collected in Lake Baikal. Features of the species; Features which may be useful in elucidating the phylogenetic relationships between dendrocoelid genera.