Baikal Research Articles

Structure and Metabolic Potential of the Microbiome of Lake Baikal Upper Sediment Layers Determined by Metagenome Analysis

Structure and Metabolic Potential of the Microbiome of Lake Baikal Upper Sediment Layers Determined by Metagenome Analysis

Application of the Pareto Front to Finding Compromise Rules for Lake Baikal Water Level Management

Application of the Pareto Front to Finding Compromise Rules for Lake Baikal Water Level Management

Predictive Assessment of Socioeconomic Damage to Coastal Areas of Irkutsk Oblast as a Result of Lake Baikal Level Fluctuations

Predictive Assessment of Socioeconomic Damage to Coastal Areas of Irkutsk Oblast as a Result of Lake Baikal Level Fluctuations

Viral Diversity in Samples of Freshwater Gastropods Benedictia baicalensis (Caenogastropoda: Benedictiidae) Revealed by Total RNA-Sequencing.

Previously, the main studies were focused on viruses that cause disease in commercial and farmed shellfish and cause damage to food enterprises (for example, Ostreavirusostreidmalaco1, Aurivirus haliotidmalaco1 and Aquabirnavirus tellinae). Advances in high-throughput sequencing technologies have extended the studies to natural populations of mollusks (and other invertebrates) as unexplored niches of viral diversity and possible sources of emerging diseases. These studies have revealed a huge diversity of mostly previously unknown viruses and filled gaps in the evolutionary history of viruses. In the present study, we estimated the viral diversity in samples of the Baikal endemic gastropod Benedictia baicalensis using metatranscriptomic analysis (total RNA-sequencing); we were able to identify a wide variety of RNA-containing viruses in four samples (pools) of mollusks collected at three stations of Lake Baikal. Most of the identified viral genomes (scaffolds) had only distant similarities to known viruses or (in most cases) to metagenome-assembled viral genomes from various natural samples (mollusks, crustaceans, insects and others) mainly from freshwater ecosystems. We were able to identify viruses similar to those previously identified in mollusks (in particular to the picornaviruses Biomphalaria virus 1 and Biomphalaria virus 3 from the freshwater gastropods); it is possible that picorna-like viruses (as well as a number of other identified viruses) are pathogenic for Baikal gastropods. Our results also suggested that Baikal mollusks, like other species, may bioaccumulate or serve as a reservoir for numerous viruses that infect a variety of organisms (including vertebrates).

Possible mechanism of the mid-high-latitude synoptic-scale disturbances impact on Meiyu precipitation anomalies

Precipitation during the Meiyu period in East Asia demonstrated a tendency towards increased frequency of rainstorms and escalating disaster-causing potential, exhibiting significant inter-annual variations in recent years. The relationship between Meiyu precipitation (MP) anomalies, related circulation anomalies and mid-high-latitude synoptic-scale disturbances was investigated by observation and reanalysis data from 1979 to 2018 and the regional climate model (RegCM4.6). Based on the observation results, the physical mechanism of disturbance affecting MP was proposed and verified by numerical simulation experiments. The results show that, during the Meiyu periods, the variation of synoptic-scale disturbances over Lake Baikal correlates negatively with MP anomalies, where the abnormal zonal winds and the disturbance anomalies show a strong spatially consistent coherence in the upper troposphere. Compared to drought years, the weaker conversion of disturbance energy to mean flow and the convergence of anomalous Eliassen-Palm (E-P) flux induce mid-high-latitude anomalous easterly flow during the Meiyu period in flood years. The occurrence of such conditions leads to the southward shift of the East-Asian subtropical jet (STJ). Then, anomalous stronger ascending flow over the Meiyu region finally results in stronger MP. In addition, warm temperature anomaly and warm advection anomaly exist at lower latitudes in flood years, while mid-high latitudes exhibit cold temperature anomaly and cold advection anomaly, which is conducive to the southward shift of the East-Asian STJ and the increase of MP. Based on the above diagnosis, sensitivity experiments were conducted using RegCM4.6. When the mid-high-latitude synoptic-scale disturbances are amplified during flood years or flood decades, the MP correspondingly decreases, and vice versa. The simulation results also show that the convergence (divergence) of mid-high-latitude E-P flux results in a weakening (strengthening) of the westerly flow, which leads to the southward (northward) shift of the East-Asian STJ. The alteration of the STJ's position in East Asia alters the position of the ascending branch of the vertical meridional circulation corresponding to the jet stream, subsequently impacting MP. Therefore, both diagnosis and numerical simulation reveal the possible mechanism of synoptic disturbances in mid-high latitude affecting MP in Yangtze River Basin, thus enriching the study of MP anomaly mechanism during Meiyu period.

First record of Microstomum lineare (Plathelminthes: Dolichomicrostomida: Microstomidae) from Lake Baikal

Specimens of the widespread microturbellarian species Microstomum lineare (Müller, 1773) were collected in the coastal zone of Chivyrkuy Bay in the northern basin of Lake Baikal at a depth of 11 m. All taxonomically significant characters of the collected specimens are fully consistent with the diagnosis of this species. This is the first reliable record of the species from Lake Baikal and from Eastern Siberia, expanding the data on the range of M. lineare and increasing the list of Baikal microstomids to two species. And furthermore, the finding of M. lineare in the lake is another example of overcoming the barrier between the Baikal and Palaearctic faunas.

Abundant production of dimethylsulfoniopropionate as a cryoprotectant by freshwater phytoplanktonic dinoflagellates in ice-covered Lake Baikal

Phytoplanktonic dinoflagellates form colonies between vertical ice crystals during the ice-melting season in Lake Baikal, but how the plankton survive the freezing conditions is not known. Here we show that the phytoplankton produces large amounts of dimethylsulfoniopropionate (DMSP), which is best-known as a marine compound. Lake-water DMSP concentrations in the spring season are comparable with those in the oceans, and colony water in ice exhibits extremely high concentrations. DMSP concentration of surface water correlates with plankton density and reaches a maximum in mid-April, with temperature-dependent fluctuations. DMSP is released from plankton cells into water in warm days. DMSP is a characteristic osmolyte of marine algae; our results demonstrate that freshwater plankton, Gymnodinium baicalense, has DMSP-producing ability, and efficiently uses the limited sulfur resource (only 1/500 of sea sulfate) to survive in freshwater ice. Plankton in Lake Baikal do not need an osmolyte, and our results clearly indicate that DMSP plays a cryoprotective role. DMSP, although a characteristic marine compound, could also be an important zwitterion for algae of other boreal lakes, alpine snow, and glaciers.

Changes in Water Balance Elements in the Basins of the Largest Tributaries of Lake Baikal in the Late XX–Early XXI Century

Changes in Water Balance Elements in the Basins of the Largest Tributaries of Lake Baikal in the Late XX–Early XXI Century

New observations on Mallomonas getseniae comb. et stat. nov. (Chrysophyceae, Synurales)

Applying of electron microscopy upgrades our knowledge on single-celled flagellates covered with siliceous scales and bristles their morphology and biodiversity. We propose a new combination and taxonomic status of Mallomonas getseniae (Voloshko) Bessudova comb. et stat. nov. based on an earlier description of scale and bristle morphology of a variety of Mallomonas striata var. getseniae Voloshko and our new data, which complement it. The species belongs to the section Striatae and have large scales, labyrinth-like reticulation on the dome and the posterior flanges with irregularly spaced large pores. The combination of those distinctive features of scale morphology is unique and allows raising the variety of M. striata var. getseniae to the species as M. getseniae. The supplement of the description of M. getseniae is based on a wide set of scales and bristles from Lake Baikal, which significantly enlarges their size variation The paper gives a first image of bristles of the species. Dynamics of occurrences of siliceous components of the species in Lake Baikal says that it develops under the ice (in March).

Summertime ENSO potentially amplifies rainstorm and flood risk in the lower Yellow River Basin, China

Study regionThe Yellow River Basin (YRB) in China. Study focusEcological conservation and high-quality development of the YRB have been incorporated into the national strategy of China. Here we investigated into the impacts of El Nino-Southern Oscillation (ENSO) on rainstorm and flood risk in the YRB, paid special attention to disaster-induced losses and explained the mechanisms of ENSO affecting the risk. New hydrological insights for the regionENSO tends to amplify rainstorm and flood risk in the YRB due to the increase in rainstorm days (rainstorm amount) by 33.6 % (34.1 %) in the next year with the previous summertime El Nino, by 20.3 % (19.3 %) in the current year with summertime La Nina, and by 70.7 % (72.5 %) in the ENSO phase shift year, and leads to a marked increase in disaster-induced losses. The summertime La Nina (El Nino) can increase the annual extreme runoff amount by 25.8 % (decrease by 8.4 %) in the lower YRB in the current year. At 500hpa, the higher air pressure over Eastern Europe and Okhotsk Sea in July, and the higher air pressure over the northern Eurasian continent and the lower air pressure over Lake Baikal and Balkhash in August tend to amplify rainstorm and flood risk. At 850hpa, the increase of water vapor transport from the south and cold air activities in high latitudes tend to increase the risk.

Quantitative Morphometric Analysis of Morphologically Similar Species of Fragilaria (Fragilariaceae, Bacillariophyta) Allows Detection of Non-Indigenous Taxa: A Case Study from Lake Ladoga (North of European Russia)

In Lake Ladoga (northwestern Russia), we found a diatom, putatively Fragilaria sublanceolata-baikali, an endemic species from Lake Baikal (southeastern Siberia, Russia). To determine whether this population matches a previously recognized species from Lake Baikal and assess how it differs from other similar Fragilaria taxa, we studied the valve morphology of three morphologically similar Fragilaria populations (the putative F. sublanceolata-baikali, F. pectinalis and F. perminuta) sampled in Lake Ladoga, along with a population of F. sublanceolata-baikali sampled in Lake Baikal. We used light and scanning electron microscopy with a combination of traditional and geometric morphometric methods. To analyze covariation between the valve shape and size (i.e., allometry), we examined differences in the ontogenetic–allometric trajectories at both the interspecific and intraspecific levels. In addition, the effect of size correction of the valve shape on species differentiation was tested. Traditional morphometrics revealed that F. sublanceolata-baikali is distinguished from F. pectinalis and F. perminuta by valve length, while F. pectinalis and F. perminuta are distinguished by striae density. All three species of Fragilaria showed separate and parallel allometric trajectories. In contrast, the two populations of F. sublanceolata-baikali were on a common allometric trajectory, indicating the conspecificity between these populations. Prior to allometric correction, geometric morphometrics was not able fully discriminate between the three Fragilaria species. After allometric correction, the three Fragilaria species were clearly separated in a size-corrected morphospace, whereas the two populations of F. sublanceolata-baikali formed a tightly overlapping group. Thus, we conclude that geometric morphometrics can reliably distinguish between these morphologically similar species of Fragilaria, but only after accounting for allometric shape variation. Our study confirmed morphological similarity between the two geographically distant populations of F. sublanceolata-baikali, which indicates that this taxon can be considered as invasive in Lake Ladoga.

The Frequency of Extreme Cold Events in North China and Their Relationship with Sea Surface Temperature Anomalies

This study investigated the interdecadal characteristics of the frequency of the winter single station extreme cold events (SSECEs) in North China and their relationship with sea surface temperature (SST). The results showed the following: (a) The SSECEs occurred frequently before 1991, but less thereafter, with an increase after 2018. The first two interdecadal modes of the SSECE frequency were east–west inverse and “n” patterns. (b) The interdecadal abrupt change of the “n” pattern occurred around 1997/1998. Before 1997/1998, the synergistic effects between the positive Interdecadal Pacific Oscillation (+IPO) and the negative North Atlantic Multidecadal Oscillation (−AMO) triggered the “two troughs and one ridge” anomalous circulation in Eurasia. The Rossby wave energy propagated downstream from the Atlantic, strengthening the Lake Baikal ridge. Furthermore, the Siberian High (SH) became weaker in the north and stronger in the south. With the favorable jet conditions, the cold air invaded North China along the northerly airflow in front of the Lake Baikal ridge, resulting in the frequent SSECE occurrence in central North China. Afterwards, the opposite occurred. (c) The cooperation of SST anomalies (SSTAs) led to the east–west inverse anomaly of the SSECE frequency. Before 1991, the high SSTAs in the central North Atlantic and low SSTAs in the equatorial Indian Ocean and the southwest Pacific triggered “+”, “−”, “+”, and “−” wave trains at mid-latitudes from the Atlantic to the North Pacific. The Rossby wave energy propagated eastward from the Atlantic, resulting in the SH and Urals ridge strengthening, and the Aleutian Low and East Asian trough deepening. The northwestern airflow in front of the Urals ridge guided the cold air into North China, leading to frequent SSECEs in central and eastern North China before 1991. The opposite occurred between 1992 and 2018.

Myxobolus nekrasovae n. sp. (Cnidaria, Myxozoa) is a new species parasitizing the gills of the gibel carp, Carassius auratus gibelio

A new Myxobolus species, Myxobolus nekrasovi n. sp., was found in the gill arch of the gibel carp Carassius auratus gibelio during investigation of fish myxosporean fauna of ponds of Lake Baikal basin. The parasites were studied on the basis of spore morphology, as well as with histological and molecular methods. Mature spores of M. nekrasovi n. sp. are ellipsoidal in frontal view and lemon-shaped in lateral view, measuring 13.84 ± 0.4 (12.2–15) μm in length, 9.73 ± 0.2 (8.5–10.7) μm in width, 6,75 ± 0.1 (6.0–7.6) μm in thickness. Polar capsules are unequal and pyriform, measuring: length 6.31 ± 0.1 (5.4–7.4), width 3.49 ± 0.04 (3.12–4) μm and length 2.88 ± 0.1 (2.1–3.5), width 1.4 ± 0.03 (1–1.6) μm. Phylogenetic analysis with the SSU rDNA gene shows Myxobolus nekrasovae n. sp. as a sister species of the subclade formed by Thellohanellus sinensis, Myxobolus acutus, M. zhaltsanovae that infect gibel carp Carassius auratus gibelio.

Sources of Hydrocarbon Gases in the Kedr Mud Volcano, Southern Basin of Lake Baikal: Results of Experimental Studies

Sources of Hydrocarbon Gases in the Kedr Mud Volcano, Southern Basin of Lake Baikal: Results of Experimental Studies

Opposite trends of cold surges over South China Sea and Philippines Sea and their different impacts on PM2.5 in eastern China

The variations in cold surge (CS) path can cause significant impacts on air pollution in the area it passes through. This study investigates impacts of CSs over South China Sea (CSSCS) and Philippine Sea (CSPHS) on PM2.5 concentrations in eastern China (PCEC) and their underlying mechanisms from 1979 to 2021. It was revealed that the CSSCS is accompanied by the continental high-pressure over East Asia and shows an upward trend. CSPHS is mainly affected by both the continental high-pressure over East Asia and the East Asian Trough over the Sea of Japan, showing a significant downward trend. Such difference in circulation anomalies is related to the different paths of the two types of CSs. Both observation and simulations indicate that more (less) Ural blocking in winter would lead to the cold air originating from the regions over Lake Baikal (Caspian Sea) to invade southward (eastward) along the northern (northwestern) path, resulting in more frequent CSSCS (CSPHS) and increased (decreased) winter averaged PCEC due to the anticyclonic (cyclonic) anomalies over eastern China. Such variations in winter averaged PCEC masked the synoptic signals that PCEC would decrease (increase) during CSSCS (CSPHS) outbreaks. Therefore, the increased frequency of atmospheric blocking over Ural Mountains in recent years has still played a worsening role in the intensification of PCEC.

Semi-Airborne UAV-TEM System Data Inversion with S-Plane Method—Case Study over Lake Baikal

The article presents the results of transient electromagnetic (TEM) prospecting surveys using an unmanned aerial system carried out at Lake Baikal, which is a unique geoelectrical setting where low-resistivity lacustrine sediments are located under a relatively isotropic water body. The task was to investigate the possibility of using a drone-based TEM survey to delineate the electrical stratigraphy of the subsurface at depths between 50 and 300 m, separated into layers and blocks. A new version of the SibGIS UAV-TEM unmanned system was used, significantly improved compared to the prototype previously described in the literature. The current switch providing bipolar current pulses connected to a grounded electrical line was the source of the electromagnetic field in the geological environment. The hexacopter carrying a measuring system consisting of 18-bit ADC and sensor—analog of 50 × 50 loop, was the receiving system. We measured survey data of 16 traverses over the Baikal going from the shore to the depths. Significant attention is being paid to a new approach to data inversion. For fast interpretation of the TEM data, we used the Sτ-method, which allows for tracing the change in the apparent longitudinal conductivity with depth. It is shown that thanks to the new sensor and current switch, the data quality has increased significantly; now, the UAV system can register sounding curves up to 1 ms. As a result, new data on the geological structure of the shelf zone of Lake Baikal were obtained. They had a good fundamental agreement with the predecessor data obtained from terrestrial measurements (from ice cover), allowing us to conclude that the UAV-TEM technology can already replace conventional ground-based electromagnetic surveys.

Low-amplitude brittle deformations revealed by UAV surveys in alluvial fans along the northwest coast of Lake Baikal: Neotectonic significance and geological hazards

Many large deltas and other areas, underlain by unconsolidated sediments, are heavily populated but impacted by various natural deformational processes. The causes and mechanisms of the deformation are often obscure because of difficulties in the identification of their geological source. We used an unmanned aerial vehicle (UAV) to survey an area of up to several km2 to detect and map surface discontinuities with displacements of a few centimeters, which can indicate the presence of initial geological deformations. We encountered such offsets in the alluvial fans on the northwestern coast of Lake Baikal, overlying the damage zones of several faults. These deformations at the different sites are referred to as primary or secondary co-seismic ruptures, brittle creep, or cryogenic fissures, which have specific origins. They are located a few hundred meters from a principal fault plane, from junctions of faults, and in the peripheral parts of alluvial fans, making these areas potentially hazardous. We analyzed the digital surface models of local segments of one of the delta plains between 2020 and 2021 and established that its periphery has subsided by an average of 5–10 cm. In areas of accumulation of the river sediment, the thickness of coarse clastic deposits has increased by approximately the same amount. Locally and in the coastal zone, the vertical surface changes are larger. In the axial parts of some seismically induced gravitational failures, the subsidence reached 33 cm over a period of 11 months and 19 days. Our results show that sediments of alluvial fans are very susceptible to various tectonic and exogenous deformational processes. The interpretation of the ultra-high resolution UAV's images can help the recognition the low-amplitude brittle deformations at an early stage of their development. Therefore, such UAV surveys are critical in the discernment of neotectonic activity and its related hazards over short observation periods.

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.

THE FIRST DATA ON MICROTURBELLARIANS (PLATHELMINTHES, RHABDITOPHORA) OF THE BOGUCHANSKY RESERVOIR. 2. THE FAMILIES MACROSTOMIDAE, MICROSTOMIDAE AND PROVORTICIDAE, WITH THE DESCRIPTION OF &lt;i&gt;BAICALELLIA NASONOVI&lt;/i&gt; SP. N.

This is the second contribution in series devoted to the study of the microturbellarian fauna (Plathelminthes, Rhabditophora) of the Boguchansky Reservoir, lower section of the Angara River, eastern Siberia. It provides information on the taxonomy, the structure of the male copulatory organ, and zoogeography of one species each from the families Provorticidae Beklemischev 1927, Macrostomidae Benden 1870, and Microstomidae Luther 1907. The faunas of these worms in the Angara River and Lake Baikal are still poorly studied. Three species from these families were recorded and described more than 90 years ago from the Angara River before our study, but the original descriptions were accompanied by highly schematic and non-informative sketches which do not allow us to perform exact species identifications and comparisons, as a rule. In the research process of the lower section of the Angara River, we found representatives of further three species: Macrostomum johni Young 1972, Microstomum rogozini Timoshkin et Krivorotkin 2023, and Baicalellia nasonovi Timoshkin et Krivorotkin, sp. n. The stylets of M. johni from the Angara River and Lake Baikal were revealed to be almost identical in structure and size to those of specimens of the type series from Great Britain. M. rogozini is one of the most common species of Microstomidae that inhabits the coastal zone of Lake Baikal. The stylet structure of Baicalellia species resembles that of Baicalellia baicali Nasonov 1930 and Baicalellia nigrofasciata Nasonov 1930, but their available descriptions do not allow us to make reliable comparisons with the species found. Therefore, we propose to consider both these names as nomina nuda and attribute those individuals to B. nasonovi, a species new to science. Despite rhe significant geographic isolation, the stylets of Baikal and Boguchan specimens are identical in structure and size. Similarly to Kalyptorhynchian species (see contribution 1), the discovery of provorticids and microstomids of Baikal origins in such a remote section of the Angara River considerably expands their distributions and demonstrates their capacities to colonize water bodies hydrographically connected to Lake Baikal. Illustrated descriptions of Boguchan and Baikal specimens of M. johni, M. rogozini and B. nasonovi, comparisons with the most similar species and zoogeographic information are given. In addition, a complete checklist of the Angara River microturbellarian fauna known so far, one currently including 35 species from nine families, is presented.

Changes in Phyto- and Zooplankton under the Climatic Shifts and Anthropogenic Load (Lake Baikal, Russia)

The hydro-chemical data collected today and structural and quantitative parameters of phyto- and zooplankton from Maloe More Strait, Lake Baikal, were analysed. Comparison of current and earlier observations revealed recent alterations in phyto- and zooplankton functions analogous to other areas of Lake Baikal. Major reconstructions in phytoplankton were registered in spring: violation in cycles of annual growth maxima of large-cell Baikalian diatoms and changes in dominant species. Dramatic abundance of rotifers caused the increase by an order of magnitude in pelagic zooplankton numbers in 2019–2020. In 2021, all of these groups were suppressed under intensive diatom vegetation. In the Mukhor bay, such changes were related to a sharp increase of rotifer numbers until 2021. In 2021, we observed decline in plankton abundance, meanwhile the relative proportion of taxonomic groups did not change with dominance of rotifers.