Search

The taxonomic diversity of hydrobionts from Listvennichny Bay was studied by DNA metabarcoding. The sequencing of a gene fragment (313 bp) of mitochondrial DNA encoding the first subunit of cytochrome c oxidase (COI) was performed using an Illumina MiSeq after amplification from internal primers (mlCOIintF, jgHCO2198). Bioinformatic analysis of COI reads revealed 187 OTUs (operational taxonomic units), among which Arthropoda, Annelida, Mollusca, and Plathelminthes prevail, accounting for 52, 30, 10, and 4%, respectively. In general, the species diversity of the bay’s fauna by the Shannon index (3.2 bits) is comparable to other areas of Lake Baikal. The most diverse composition of taxa (22 OTUs) of the species rank falls on the larvae of chironomids, which confirms the effectiveness of the method for identifying juvenile stages of invertebrates. The research results are the first step toward improving the system of hydrobiological monitoring of Lake Baikal based on the synthesis of molecular genetic diagnostics of invertebrates and classical morphological taxonomy.

We investigated the diversity of benthic algal communities as well as phytoplankton in Lake Baikal. The structure of benthic algal communities changed in comparison to the period before 2000 due to intense development of filamentous algae, particularly Spirogyra. Percent cover of filamentous algae in different areas of the coastal zone varied from 0 to 100%. The lowest Spirogyra biomass was recorded in the surf and wave-breaking zones, whereas the highest biomass was observed in the area of the bottom less affected by waves. Fragments of Spirogyra thallomes were also recorded in the phytoplankton community of Lake Baikal's southern basin which is a new phenomena not previously recorded in the lake. Hydraulic characteristics of Spirogyra were similar to those of planktonic diatoms. Currents and wave effects on the bottom favored transfer and distribution of Spirogyra from locations with intense development to the coastal area of Lake Baikal. Spirogyra is now found throughout Lake Baikal.

Within the framework of the monitoring of the Baikal endemic sponge fauna, which was started in 2015, we organized field observations. This study is aimed to investigate the dynamics of the disease incidence in sponges and the rate of their degradation/regeneration in the natural environment within a limited space. The observations of the tagged sponges having different shapes were carried out using the photo and video method. Thus, from 2016 to 2018, there was a deterioration dynamics in the state of most control sponges. From 2018 to 2019, the state of some sponges improved owing to the regeneration of the affected areas of the body. In this study, we revealed that Baikal sponges with encrusted and globulous shapes could recover very quickly owing to the regeneration of the affected areas and the rapid growth of the body. After almost complete degradation of the body in the encrusted sponge, the fragments remain, which can subsequently grow as individual specimens. Similar observations are currently being conducted throughout Lake Baikal.

Recent studies have revealed how the freshwater biota of Lake Baikal responds to climate change and anthropogenic impacts. We studied phyto- and zooplankton, as well as phyto- and zoobenthos, in the open coastal waters of the southern basin of the lake and of Listvennichny Bay. A total of 180 aquatic organism taxa were recorded. The response of the Baikal ecosystem to climate change can be traced by changes in the species composition of planktonic communities of the lake’s open coasts in summer. The key species were thermophilic the Anabaena lemmermannii P. Richt. (Fij = +0.7) blue-green algae, the Asplanchna priodonta Gosse (Fij = +0.6) rotifers in 2016, the Rhodomonas pusilla (Bachm.) Javorn. (Fij = +0.5) cold-loving algae, and the Cyclops kolensis Lilljeborg (Fij = +0.9) copepods in the past century. The proportion of Chlorophyta decreased from 63% to 17%, the Cyanophyta increased from 3% to 11% in the total biomass of phytoplankton, and the proportion of Cladocera and Rotifera increased to 26% and 11% in the biomass of zooplankton, respectively. Human activity makes an additional contribution to the eutrophication of coastal waters. The Dinobryon species, the cosmopolitan A. formosa and F. radians, dominated phytoplankton, and filamentous algae, Spirogyra, dominated at the bottom in the area with anthropogenic impact. The trophic level was higher than at the unaffected background site: the saprobity index varied from 1.45 to 2.17, the ratio of eutrophic species to oligotrophic species ranged from 1:2 to 3:1, and the ratio of mesosaprobiont biomass to endemics biomass ranged from 2:1 to 7:1. Currently, the boundaries of eutrophication zones of shallow waters in Lake Baikal are expanding, and its coastal zone has acquired features typical of freshwater bodies of the eutrophic type.

We have studied the diversity and composition of communities of micro-eukaryotes from two localities: area under anthropogenic impact near the town of Baikalsk and reference area, Irinda Bay, based on high-throughput ITS2 rDNA region sequencing. High taxonomic diversity of micro-eukaryotes has been revealed in both localities studied. However, micro-eukaryotic community from the area under anthropogenic impact is depressed, compared to reference area. Analysis of taxonomic diversity has revealed that community from the area under anthropogenic impact has a trend towards a decrease in diversity. Among the detected taxa, detected Alveolata, Stramenopiles and Fungi prevailed. Sorensen index of OTUs was 65%, which indicates the similarity of communities studied by taxonomic composition. The spectrum of Alveolata and Stramenopiles taxa identified in the area under the anthropogenic impact and the reference area was similar. The main differences were revealed in spectrum of Fungi taxa.

Sponges are an ecologically important component of marine and freshwater bodies. Sponge community includes a variety of microorganisms: fungi, algae, archaea, bacteria and viruses. Despite active research in the field of aquatic virology, biodiversity and the role of viruses in sponges are poorly studied. The relevance of research in this area is also related to the worldwide problem of sponge diseases. The aim of this study was to elucidate the genetic diversity of viruses in the associated community of diseased endemic Baikal sponge Lubomirskia baikalensis using metagenomic analysis. As a result, we have shown for the first time a high genetic and taxonomic diversity of DNA viruses in the Baikal sponge community. Identified sequences belonged to 16 viral families that infect a wide range of organisms. Moreover, our analysis indicated the differences in viral communities of visually healthy and diseased branches of the sponge. The approach used in this study is promising for further studies of viral communities in sponges, obtaining more complete information about the taxonomic and functional diversity of viruses in holobionts and entire Lake Baikal, and identifying the role of viruses in sponge diseases.

We have studied the fauna of Hydra the waters of the Baikal region using morphological and molecular genetic methods. By the external morphological features of the structure of the polyp and the microscopic study of nematocysts, we have identified four species belonging to three different genetic groups: “oligactis group” (Hydra oligactis, H. oxycnida), “braueri group” (H. circumcincta) and “vulgaris group” (H. vulgaris). Molecular phylogenetic analysis has confirmed the species status of the hydras studied. The intraspecific genetic distances between the Baikal and European hydras are 1.5–4.2% and 0.4–2.7% of the substitutions in COI and ITS1–5.8S–ITS2 markers, respectively, while, interspecific distances for different species significantly exceed intraspecific and amount to 9.8−16.1% and 6.4−32.1% of substitutions for the markers COI and ITS1–5.8S–ITS2, respectively. The temperature regime of the water and the availability of food resources, which play a key role in the reproduction of hydras, determine the habitats of the identified species. The research performed has replenished the regional fauna with species whose findings were previously considered presumptive or doubtful. The first record of H. vulgaris in the artificial reservoir near the Angara River (Lake Kuzmikhinskoye) will help to clarify the distribution of this species.

Sponges are ecologically important components of marine and freshwater benthic environments; these holobionts contain a variety of microorganisms and viruses. For the metagenomic characterization of potential taxonomic and functional diversity of sponge-associated dsDNA viruses, we surveyed two samples of Baikal endemic sponge Baikalospongia bacillifera (diseased and visually healthy). In total, after quality processing, we have obtained 3 375 063 and 4 063 311 reads; of these 97 557 and 88 517 sequences, accounting for ca. 2.9 and 2.2% of datasets, have been identified as viral. We have revealed approximately 28 viral families, among which the bacteriophages of the Myoviridae, Siphoviridae and Podoviridae families, as well as the viruses of the Phycodnaviridae and Poxviridae families, dominated in the samples. Analysis of viral sequences using the COG database has indicated 22 functional categories of proteins. Viral communities of visually healthy and diseased Baikal sponges were significantly different. The metagenome sequence data were deposited to NCBI SRA as BioProject PRJNA577390. Keywords: Metagenomics, Viral communities, Viral diversity, Virome, Sponge holobiont, Freshwater sponges, Lake Baikal

Molecular phylogeny inferred from rbcL nucleotide sequences obtained from the single sterile filaments of green algae collected around the perimeter of Lake Baikal indicates the polyphyletic origin of the representatives of genus Spirogyra Link., 1820 inhabiting the lake. The common ancestor of all Baikal Spirogyra dates back at least to 20 MYA. This roughly coincides with the age of continuously existing freshwater body in the confines of current Baikal. The descendants of this node include both Baikal and non-Baikal species and thus suggesting a complex history of multiple emigrations and immigrations. There is at least one major lineage of the Baikal Spirogyra in the phylogeny descending uninterruptedly from the common ancestor of all Spirogyra species found so far in the lake. The likely explanation is its permanent presence in the ecosystem. All this allows us to hypothesize that the current bloom is a spectacular but natural response of the Baikal ecosystem to the increased pollution.

In this paper, molecular analyses of Baikal hydras from the ‘oligactis group’, based on COI and ITS1–5.8S–ITS2, and morphological analysis of their holotrichous isorhizas, were performed. Low genetic diversity and shared haplotypes were found between Hydra oligactis Pallas, 1766 and Hydra baikalensis Swarczewsky, 1923 specimens, which is evidence of the mixing of these lineages. Genetic distances among all Baikal hydras (0.006) were less than the interspecific distances of other hydras. The size of hydras and proportions of their holotrichous isorhizas varied depending on microhabitat and environmental conditions. Our combined molecular and morphological approach proves that H. baikalensis is synonymous with H. oligactis

The spatial distribution of healthy and diseased sponges in Lake Baikal was investigated. The endemic sponges were studied in May − June 2015 at 11 transects within the depth range of 0 to 40 m. More than 500 sponge specimens were collected, and 29 taxa including 12 species and 17 morphospecies (sp. taxa) were identified. Among the 29 taxa, only B. martinsoni specimens and 14 morphospecies were healthy, whereas specimens of the other 11 species and 3 morphospecies were diseased, making up 35% of the total number of specimens (512). The different body forms of sponge found among the specimens were encrusting (66%), globulous (21%), and branched (13%). Sponges with necrosis signs, discolored specimens or covered with violet film or brown spots, were found in all transects under study (37 stations of 68). The percent cover of the bottom (per m2) by various body forms of sponges was evaluated with a sponge faunal state assessment test. Changes in the diversity and abundance of sponges due to their disease may jeopardize the functioning of the entire ecosystem of Lake Baikal which is a World Heritage Site. This baseline data on patterns of sponges, including their spatial distribution and percent cover, will be utilized to support future management and monitoring of Lake Baikal. Data on the current state of Baikal endemic sponge fauna are essential for understanding the causes and prognosis of disease processes of freshwater sponges.

The diversity of algal communities of phytoplankton and meio-and macrophytes was investigated in Lake Baikal. Fragments ofSpirogyrathallomes were recorded in the phytoplankton community of Southern Baikal, which had never been recorded before in its composition. It was also established that the structure of benthic algal communities changed in comparison with that in 2000 due to intense development of filamentous algae, particularlySpirogyra. Its lowest biomass was recorded in the surf zone and wave breaking, whereas the highest biomass was registered in the area of weakened effect of waves on the bottom. The cover percent of the bottom with filamentous algae in different areas of the coastal zone varied from 0 to 100%. Hydraulic characteristics ofSpirogyrawere the same as those of planktonic diatoms. The circulation currents and wave effect on the bottom favoured transfer and distribution ofSpirogyrafrom the location of its intense development into the coastal area of Lake Baikal.

A local eutrophication process is noted for the first time in Listvennichnyi Bay in Lake Baikal. Using morphological and molecular-genetic methods, species of filamentous green algae that form mats at site of the lake subjected to anthropogenic impact are identified. The presence of species of the genus Spirogyra Link., atypical for this part of the lake, as well as their distribution, together with species Ulothrix zonata (Web. et Mohr) Kurz. in an atypically large depth, indicates the serious disturbance of the structure of plant community of the studied site of Baikal.

The evolutionary history of two species belonging to the genus Orthocladius van der Wulp, 1874 (Diptera: Chironomidae) from Lake Baikal was investigated using the mitochondrial gene coding the first subunit of the cytochrome c oxidase (CO1 mtDNA). The phylogenetic analysis indicated that the Baikal Orthocladius species were divided into two well-defined clades where O. (Orthocladius) gregarius Linevitsh, 1970 was a sister species to Palaearctic O. (Orthocladius) nitidoscutellatus Lundstrom, 1915 and the O. (Eudactylocladius) sp. was a sister species to Nearctic O. (Eudactylocladius) subletteorum Cranston, 1998. Divergence time estimates indicated that these species had been evolving independently for about 18 Ma (Neogene, Early Miocene), while emergence of the most recent common ancestors of the modern O. (Orthocladius) gregarius and O. (Eudactylocladius) sp. was dated to about 3.5 Ma (Neogene, Pliocene). The evolution of Baikal orthoclads occurred from the rheophilic fauna under conditions of global clim...

For the first time, species of the genus Spirogyra , non-typical of the open nearshore waters of Lake Baikal, formed algal mats with Ulothrix zonata , Ulothrix tenerrima , and Ulothrix tenuissima near the village of Listvyanka, Russia. Normally widely distributed in the 0- to 1.5-m depth range, the growth of U. zonata was now evident and dominant (63% of the biomass) in the 2- to 5-m depth range. The overgrowth of the lake bottom by filamentous green algae, changes in distributional boundaries, the emergence and mass development of species of the genus Spirogyra , the presence of the eutrophic diatom indicator Fragilaria capucina var. vaucheriae , elevated abundances of coliform bacteria, and elevated levels of nutrients suggest an early stage of cultural eutrophication in the nearshore of Lake Baikal near Listvyanka, a popular tourist destination. The unusual abundance of Fragilaria associated with the filamentous green algae consisted of long-ribbon colonies of F. capucina var. vaucheriae , a eutrophic species, wound around the filamentous green algae, enhancing the dense algae mats. Historically dominant species, such as Didymosphenia geminata , Tetraspora cylindrica var. bullosa , and Draparnaldioides baicalensis typically observed at deeper depths of Lake Baikal, are now subdominants or minor species in the nearshore along the shoreline near Listvyanka.

Background. A local eutrophication process is noted for the first time in Listvennichnyi bay in Lake Baikal. High level of biogenic elements in the water of the bay led to nuisance growth of filamentous algae. Rapid identification of these algae's taxa was necessary to assess ecosystem damage in the polluted area of the lake. Materials and methods. We determined a boundary of bottom fouling by locating transects ranging from 0 to 10 meters in different areas of the bay. Algae samples were examined using microscopic techniques as well as SSU 18S rDNA sequencing. Phylogenetic trees were estimated using Bayesian inference (BI) based on SSU alignment. Results. Our results showed intensive filamentous algae fouling in depth from 3 to 10 meters along the coastline of the eastern part of the bay. Morphological and molecular analysis demonstrated prevalence in samples of Ulothrix zonata (Web. et Mohr) Kütz. Using SSU 18S rDNA sequencing data we also showed presence of three species of Spirogyra Link. genus. Conclusion. Detection of Spirogyra species which are normally not typical for such areas of the lake along with Ulothrix zonata extended more deeply than usually observed reveals severe phytocenosis disturbance of the polluted part of Lake Baikal.

The phylogenetic relationships between Baikalian endemic green alga Draparnaldioides simplex C. Meyer et Skabitch., 1976 and holarctic taxa of green algae have been studied using the 18S rDNA gene fragment and internal transcribed ITS1 and ITS2 spacers of nuclear DNA. The Baikalian genus Draparnaldioides was shown to be a separate taxon. The level of genetic difference between the studied species and non-Baikalian taxa of sister groups of green algae is insignificant, which indicates the young age of the genus Draparnaldioides and its recent radiation from the common ancestor with genera Draparnaldia and Chaetophora.

We carried out a first study of Lake Baikal epiphyton on six species of submerged macrophytes: Myriophyllum spicatum L., Potamogeton perfoliatus L., Potamogeton sp., Sparganium gramineum Georgi, Ceratophyllum demersum L., and Elodea сanadensis Michaux. We identified 70 epiphyton species and intraspecific taxa belonging to 3 phyla, viz. Ochrophyta, Cyanobacteria, and Chlorophyta. Nine species of Cyanobacteria were new records for Lake Baikal. Epiphyton communities differing in species composition and quantitative characteristics grew on diverse species of submerged macrophytes. High levels of species richness were recorded on Sparganiumgramineum and Potamogeton sp., whereas low diversity of epiphyton was observed on Myriophyllum spicatum and Elodea canadensis. A monodominant community was revealed on the invasive Elodea canadensis represented by Cocconeis placentula var. placentula. Specific characteristics of morphology of submerged macrophytes influenced the structural organization and quantitative development of epiphyton. Epiphyton abundance and biomass were higher on upper sections of most plants than on lower sections, probably because of canopy shading of macrophyte lower portions.

The phylogenetic relationships of the Baikal endemic chironomid Paratanytarsus baicalensis (Tshern.) and other representatives of the tribe Tanytarsini were studied using 117 partial sequences of the mitochondrial COI gene from 33 species of the genera Paratanytarsus and Micropsectra. The results show that the Baikal species is close in origin to two geographically distant European species, P. austriacus and P. hyperboreus, and itself splits into two genetically distinct clades.

The spatial distribution of Elodea canadensis Mich. was studied in the southern and central basins of Lake Baikal in 2006–2009. E. canadensis has naturalized successfully in the lake ecosystem. It coexists here with the indigenous submerged macrophytes under its canopy or forms either rarefied undergrowth or separate monomorphic spots. The invasion of this species into the Lake Baikal ecosystems has led to the structure reorganization of indigenous phytocenoses in several bays of the Maloye More. Currently, E. canadensis dominates in phytocenoses of Khuzhir-Nugo Bay; and Myriophyllum spicatum L., in Kurkutskaya Bay. The trend of the population dynamics in these two species was observed, common to the Lake Baikal and other fresh-water ecosystems, where a decrease in E. canadensis abundance is followed by an increase in M. spicatum abundance. The abundance and distribution of the associated biota of submerged macrophytes was studied. It was found that the phytoepiphytone community of E. canadensis differed significantly compared to the indigenous submerged macrophytes inhabiting the same biotope. Low values of Shannon-Weaver index, high abundance of one species (Cocconeis placentula var. placentula), and low evenness are evidence of community vulnerability and unfavorable conditions of its habitat on E. canadensis. That is why, when E. canadensis forms thickets, a decrease in biodiversity of phytoepiphytone and dominance of Cocconeis species are usually observed. Structural changes of phytocenoses influence on the abundance of invertebrates. Epibiota of Elodea canadensis differs significantly from that on Myriophyllum spicatum and bottom fauna, which the results of principal component analysis and ANOVA confirm.

The body size of larvae and the age structure of populations of three chironomid species (Chironomidae) from the Lake Baikal littoral was studied. Young larvae 1.0–2.6 mm long were abundant during the whole period investigated (August 2000–August 2001). Parameters of the equation that allows determining the weight of midge larvae by the width of their head capsule or by their body length were calculated for Paratanytarsus baicalensis, Orthocladius nitidoscutellatus, and Orthocladius sp.

The population structure of endemic species Sergentia baicalensis (Diptera, Chironomidae) from Lake Baikal was studied using the first subunit of the cytochrome C oxidase mitochondrial gene (Col). Two populations inhabiting different basins of this lake, the southern-central and northern, were detected. It was confirmed that the divergence time of this species was dated to Late Miocene (9.53 ± 3.9 Mya), during the period when geographically separated basins existed in the Baikal rift zone.

The development of a fouling community at the surface of an artificial substrate in the littoral zone of Lake Baikal was studied. This epibenthic community was composed of 23 diatom species and 57 invertebrate species. The core community consisted of molluscs and caddisflies feeding mostly on diatoms. In Lake Baikal a fouling community develops in a sequence similar to marine environments.

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.

In shallow water areas of open Lake Baikal, filamentous green alga of the genus Spirogyra grows abundantly. Together with alga of the genus Ulothrix, it forms algal mats. According to our observations from 2010 to 2013, the spawning habitat conditions for the yellowfin sculpin Cottocomephorus grewingkii (Dybowski, 1874) (Cottidae) proved to be significantly disturbed in the littoral zone of Listvennichnyi Bay (southern Baikal), which, in turn, reduced the number of egg layings. With a 100% projective cover of the floor and a high density of green filamentous algae, the shallow-water stony substrate becomes completely inaccessible for spawning of the August population.

Phylogenetic relationships between the endemic baicalian green algae Draparnaldioides simplex C. meyer et Skabitsch, 1976 and holarctic taxa of green algae were studied using the fragment of 18S rDNA and internal transcribed spacers ITS1 and ITS2 of nuclear DNA. We showed that the baicalian genus Draparnaldioides is a separate taxon. The genetic difference between Draparnaldioides and nonbaicalian taxa of the sister groups of the green algae are small enough to indicate relative youth of the genus Draparnaldioides and its recent radiation from a common ancestor with Draparnaldia and Chaetophora.

The faunal composition, structure of the zoobenthos communities, and seasonal changes in two springs in the south of Irkutsk area are investigated. Both springs have the water temperature 4-5 degrees C all year round. The fauna consists of widely distributed hydrobionts, crenobionts, stygobionts, and near-water organisms. Arctic relicts and elements of the Lake Baikal fauna are found. In macroinvertebrate communities, chironomid larvae dominate (by abundance and biomass), as do oligochaetes (by abundance). The lowest quantitative parameters are recorded in autumn-winter, and the highest parameters, in spring (March-April). Then they abruptly decline owing to emergence of amphibiotic insects. The structure of spring communities has regional specificity. By biomass of macrozoobenthos, the springs are comparable with mesotrophic and even eutrophic lakes.

The Chernobyl accident resulted in environmental radionuclide pollution in many areas, including the Dnepr river. The water and fish of the Kakhovsk Water Reservoir were under study and tested for 90Sr and 137Cs. It was found that the content of 137Cs achieved pre-accident levels and that of 90Sr was 4-6 times higher than that prior to the accident. The fish levels of the above radionuclides were 10-20 times as high as the pre-accident levels. Due to the consumption of fish, the radiation doses of the radionuclides, mainly 90Sr, in the population living in the costal areas of the Kakhovsk Water Reservoir were 20-30 times higher than the pre-accident levels.