A study of macroinvertebrate communities in Bolshiye Koty Bay of Lake Baikal using DNA metabarcoding.

The diversity of macroinvertebrates, the structure of their communities in Bolshiye Koty Bay (Lake Baikal) was studied by a DNA metabarcoding approach using an Illumina MiSeq system. Internal primer mlCOIintF in combination with jgHCO2198 of the Folmer fragment of the COI gene were used for macroinvertebrate metabarcoding. A total of 118009 reads of the COI gene fragment (at least 313 bp in length) were obtained. The correlation of the Spearman coefficient (S = 0.6, p<0.05) with the abundance of macroinvertebrates in the samples before DNA extraction showed that the number of reads can serve as an indirect characteristic of the abundance of a species (operational taxonomic unit, OTU). 115 OTUs belonging to the higher taxa of macroinvertebrates were identified: Porifera, 1; Platyhelminthes, 3; Annelida, 38; Arthropoda, 55; Mollusca, 18. At a high level of resolution (with homology with GenBank reference sequences ≥ 95 %, coverage ≥ 90 %), 46 taxa of macroinvertebrates comprising three communities were registered: one dominated by molluscs (Choanomphalus conf. maacki) and two dominated by chironomids (Orthocladius gregarius Linev., Sergentia baicalensis Tshern.). Communities are characterized by low species diversity according to Shannon (from 0.7 to 1.2 bits), high concentration of dominance according to Simpson (from 0.5 to 0.7) and low evenness according to Pielou (from 0.3 to 0.4). Dominants and subdominants in the communities account for 91 to 96 % of COI gene fragment reads. The spatial distribution of the dominant species identified in the communities is influenced by the geomorphological features of the bottom and the composition of sediments in the area studied. The approach proposed for studying the structure of macroinvertebrate communities based on DNA metabarcoding and next generation sequencing can be recommended for express assessment of the state of aquatic ecosystems in the monitoring.

DNA metabarcoding of benthic algae and associated eukaryotes from Lake Baikal in the face of rapid environmental changes.

Here we report new data describing the biodiversity of phytobenthic communities based on DNA-metabarcoding using the 18S rDNA marker and the Illumina MiSeq system. The study was initiated due to the blooming of f ilamentous algae (mainly of the genus Spirogyra) and cyanobacteria in the coastal zone of Lake Baikal under climate change and anthropogenic impact. The composition and taxonomic diversity of algae and other organisms associated with them on different sites of Lake Baikal (near Bolshoi Ushkaniy Island, in Listvennichny Bay) and in the Kaya (within the city of Irkutsk, located in the same drainage basin as Lake Baikal) were determined using DNAmetabarcoding. About 15 thousand reads of the 18S rRNA marker were obtained by applying NGS (next-generation sequencing). The species of algae dominating in the number of reads, as well as the diff icult-to-identify taxa (Stramenopiles, Alveolata, Euglenozoa, Chromista, Rhizaria, Amoebozoa, etc.), which play an important role in the functioning and formation of the structure of algal communities, were revealed. The Shannon index of the communities studied ranges from 1.56 to 2.72. The advantages and weaknesses of using DNA-metabarcoding based on the 18S rRNA gene fragment for studying the structure of algal communities are shown. The advantage of this method is the possibility to more fully determine the diversity of eukaryotes taxa, which are diff icult to identify by morphology, without involving a large number of specialists, while the disadvantage of the method is the distortion that may occur during the PCR. Here, ways of solving this problem are proposed. The results of the study show that the analysis of the minor component of the eukaryotic community in samples (organisms with low biomass) consisting of a mixture of multicellular and unicellular organisms requires a read-depths of at least 100,000 sequences per sample. In general, the DNA-metabarcoding method is recommended for studying the structure of algal communities and eukaryotes associated with them.

The effect of bloom of filamentous green algae on the reproduction of yellowfin sculpin Cottocomephorus grewingkii (Dybowski, 1874) (Cottoidae) during ecological crisis in Lake Baikal.

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.

[Genetic Differentiation of Populations of Baikal Endemic Sergentia baicalensis Tshern. (Diptera, Chironomidae)].

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.

[Evolutional relationships of endemic green algae Draparnaldioides simplex from Lake Baikal with nonbaicalian taxa of family Chaetoforaceae (Chlorophyta)].

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.

[Zoobenthos communities and their seasonal dynamics in nonfreezing springs of Baikal region].

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.

[Radiation doses in the population of the coastal area of the Kakhovsk Water Reservoir]. / Dozy oblucheniia naseleniia pribrezhnoi zony Kakhovskogo vodokhranilishcha.

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.