The Current Oxygen and Hydrogen Isotopic Status of Lake Baikal

This study revises the δ18O and δ2H status of Lake Baikal. The mean values of δ18O and δ2H varied from −15.9 to −15.5‰ and from −123.2 to 122.2‰, respectively, for the past 30 yr. The isotopic composition of the lake remained more ‘‘light” compared to the regional precipitation and rivers inflows. The isotopic composition of the lake has begun to change since ca.1920 after the Little Ice Age; however, Lake Baikal still has not reached the isotopically steady state in the present. The calculated composition of the steady-state should be −12.3‰ for δ18O and −103.6‰ for δ2H. If regional climate parameters do not change dramatically, Lake Baikal will reach these values in ca. 226 yr. Based on isotopic fingerprints of the upper (0 to 150 m) and near-bottom layers (ca. 150 m from the bottom floor), the renewal in the southern and central basins of Lake Baikal has occurred recently compared to the northern Baikal basin, and the size of the mixing-cell of downwelling is close to 30 km.

Volcanic rocks and pseudotachylytes from sources of crust-mantle complementary layers: Insight into geodynamics of the Baikal Rift System, Southern Siberia

<p>We present results of detail geochemical study of 18–12 Ma volcanic rocks from the Kamar-Stanovoy Zone of Hot Transtension (KSZHT), located in the central Baikal Rift System (BRS), and older pseudotachylytes from the Main Sayan Fault (MSF). These rocks designate geochemically distinguished from the OIB sources that are referred to the Slyudyanka zone of paleocollision occurred between the Khamardaban terrane and Siberian paleocontinent about 488 Ma ago. We define crustal and mantle signatures (with and without garnet, respectively) for the KSZHT volcanic rocks and crustal ones for the MSF basic pseudotachylytes. The signatures are indicative for tracing complementary relations between layers of the crust–mantle transition (CMT). We infer that the KSZHT volcanic activities accompanied rifting of a paleocontinental margin but got quiescent after a structural separation of the South Baikal Basin from the Tunka Valley, when the former had been sufficiently extended and subsided in contrast to the latter, which had been notably compressed and uplifted. From geological evidence and a detail seismic tomography model, we suggest that the KSZHT crust–mantle magmatic processes were due to delamination of a thickened root part of the South Baikal Orogen that preceded rifting in the South Baikal Basin area in the Late Cretaceous and Paleogene. Volcanic rocks of the past 17 Ma from the southwestern BRS denoted similar CMT sources and delamination processes beneath the East Hangay orogen and adjacent Orkhon-Selenga saddle. In the central and southwestern BRS, the CMT sources marked mutually overlapping deformational fields related to Indo-Asian convergence and pool-to-axis forces of the Japan-Baikal geodynamic corridor.</p><p>This work is supported by the RSF grant 18-77-10027.</p>

First Findings of Sunbleak Leucaspius delineatus (Cyprinidae) in the Lake Baikal Basin

Since the early 1960s, the sunbleak Leucaspius delineatus (Heckel, 1843), along with carp acclimatized from European Russia, regularly entered the siberian carp ponds, first in the Ob’ basin, and then in the Yenisei and Angara basins. In the last decade, we have discovered the sunbleak in two water bodies of the Baikal basin: in May 2013 - in the water intake and discharge canals of the Gusinoozersk regional power plant situated on the large lake Gusinoe in the Selenga River basin (Republic of Buryatia), and in November 2016, the sunbleak was registered in the diet of pike inhabiting the reservoirs of the Talaya-Pokhabikha lake-bog complex in the immediate vicinity of the Baikal coastline at the southern end of the lake in Irkutsk Region. The age series in the samples of the sunbleak in the water intake canal of the power plant was represented by five age groups from 1+ (SL 34.2 mm and 0.59 g of weight) to 5+ (SL 73.9 mm and 6.73 g, respectively) with a predominance of individuals aged 1+ and 2+. In the discharge canal only group 1+ (SL 35.5 mm and 0.69 g) was noted. The sex ratio in catches at the age of 1+ was 1:1.2 with a predominance of males; by the age of 3+, the proportion of males increased significantly (1:8.6). Sexual maturity of the sunbleak from Lake Gusinoe occurs at the age of 3+. Spawning is portioned, the first portion is layed down not earlier than the second half of July. The total fecundity of the seven studied females at the age of 3–5 + varies from 632 to 1539 eggs, averaging 1312 eggs. The sunbleaks from Lake Gusinoe are predominantly benthophagous. In the first half of May 2013, near the water intake canal, the main food components were the nymphs of the Corixidae water bugs and larvae of Phryganea caddis flies, planktonic crustaceans and imago of aerial insects were also consumed. In July 2014, in the discharge channel, the main food item was the chironomid larvae. In the lake Sludyanskoye, three specimens were identified from the stomachs of the pike living there. All fish were partially digested, and therefore it was not possible to analyse it.

Landscape-Cartographic Analysis of Changes in the Taxonomic Diversity of Soils Zoocenoses in Baikal Region

The paper presents a landscape-ecological analysis of the mesopopulation structure of the geosystems in the Baikal region. The regularities of changes in the quantitative characteristics and taxonomic diversity of invertebrate communities in the landscape-ecological range under the influence of natural and anthropogenic factors at different levels of the organization of geographical space are considered. The data were obtained as a result of a detailed study of the quantitative characteristics of invertebrate communities in the key polygons of the taiga, mountain-taiga and steppe geosystems of the Lake Baikal basin. Numerous cartographic materials, information about the soil cover and the state of vegetation are analyzed, data on the heat supply and moisture supply of soils are taken into account. The main trend of changing the diversity of pedobiont communities is a decrease of species number in the gradient of increasing aridity of the climate, increasing hypothermia and anthropogenic pressure. Based on the data obtained, the map “Taxonomic diversity of soil-biotic communities in the geosystems of the Lake Baikal basin” is presented. Conservation of biological diversity is considered as one of the most important conditions for sustainable development and rational use of natural resources.