I. V. Tomberg

The Selenga River water quality on the border with Mongolia at the beginning of the 21st century

Based on the comprehensive hydrochemical and hydrobiological studies of the Selenga River near the Naushki settlement carried out in 2010, the quality of water flowing from the territory of Mongolia is assessed. The comparison with the results of the previous years indicates that the water quality deteriorated due to the intensification of economic activity in the river basin and unfavorable climatic factors.

Space and Time Variations in Concentrations of Biogenic and Organic Matter and Phytoplankton in the Water of the Selenga River and Its Delta Branches

Specific features of the concentration dynamics of biogenic substances, organic C, and phytoplankton in the lower reaches of the Selenga and its delta branch are identified. The quantitative and qualitative changes in these components are demonstrated for the conditions of extremely low water abundance. High correlation was shown to exist between variations of the concentrations of nitrate N, mineral P, and phytoplankton biomass.

Water chemistry and phytoplankton in water bodies in the Selenga River’s delta under ice cover

Results of comprehensive studies that were carried out during freezing period in the lower reaches of the Selenga River and in water bodies located within its delta revealed peculiarities of water chemistry, phytoplankton species composition, and the characteristic features of alga development. Quantitative assessment of algae is also presented.

Changes in phytoplankton community composition along a salinity gradient from the lower Yenisei River to the Kara Sea, Russia

Abstract Changes in phytoplankton community composition related to salinity, allochthonous matter, and nutrients were found in the mixing zone that extended from the outflow of the lower Yenisei River into the Yenisei Gulf and Kara Sea in Russia. The highest cell abundance (140–662×103 cells m-3), biomass (138–950 mg m-3) and species diversity were found in the freshwater area (i.e., the lower reaches of the Yenisei River). The river-sea transition was marked by a decrease in the relative abundance of green algae and cyanobacteria, but an increase in chrysophyte algae. The ratio of freshwater and marine phytoplankton species was quantified in each habitat. The results contribute to our understanding of biological processes in the estuaries of large rivers flowing into the shelf zone of the Arctic Ocean.

Chemical composition characteristics of water and phytoplankton development in Lake Zavernyaikha

Based on long-term observations, we examine the seasonal and interannual dynamics of the phytoplankton and chemical composition of the water in Lake Zavernyaikha located in the delta of the Selenga river. The study revealed an intense development of five kinds of phytoplankton under the ice, dominated by dynophytes: Baikal’s endemics G. baicalense and P. baicalense. The main factors for massive algae development under the ice are: the favorable gaseous regime and relationship of nutrients, high content of readily hydrolizable organic matter (RHOM), isolatedness of the water body, and high division rate of dinophytes.

Current chemical composition of Lake Baikal water

Abstract Habitats of organisms in Lake Baikal have been comprehensively monitored for many years. In 2010–2015, we conducted 8 research expeditions to study ionic composition of the water and measure concentrations of dissolved oxygen, nutrients, organic carbon, and persistent organic pollutants in the entire pelagic area of Lake Baikal. Our data showed that the ionic composition was stable at all depths in the pelagic zone of the lake. We also recorded seasonal variability, vertical stratification, and spatial variations in the content of nutrients, organic matter, and gas components. The concentrations of major ions, nutrients, and dissolved oxygen were favourable for the growth of hydrobionts in the offshore pelagic zone. Concentrations of pollutants in Lake Baikal, such as persistent organic pollutants and heavy metals, were low and did not directly affect the biota. The water in specific areas of the littoral zone of Lake Baikal, however, was polluted near large settlements (Listvyanka, Severobaikalsk, Baikalsk, and Slyudyanka) and in bays because of unsatisfactory operations of sewage treatment plants, growing tourist activity, and intense ship traffic. Continuing investigations are needed to elucidate causes of eutrophication in the littoral zone of Lake Baikal.

Assessing the Water Quality in the Tributary Streams of Lake Baikal From Chemical Parameters

On the basis of hydrochemical investigations from 2010–2012 and with due regard for earlier data, we assess the present status of water quality for the main tributary streams of Lake Baikal. An analysis is made of the observed changes in the chemical composition of water induced by natural and anthropogenic factors. It is shown that the deterioration of the water quality in the Selenga river and in the small tributaries of South Baikal, respectively, is caused by wastewater discharges and by pollution of atmospheric precipitation, respectively.

Concentration dynamics of biogenic elements and phytoplankton at Selenga R. Mouth and in Selenga shallows (Lake Baikal)

The seasonal and year-to-year dynamics of the concentrations of biogenic elements and organic matter, as well as quantitative composition of phytoplankton in water of Selenga delta branches is studied. The distribution of those components from the mouth of the Kharauz branch (the main branch) to the water area of the Selenga shallows in different hydrological seasons is shown. The concentrations of nitrate nitrogen and phosphate phosphorus in the zone of mixing of river and lake waters have been found to drop by 30 and 50%, respectively, because of the consumption of those substances by phytoplankton.

Silica-Scaled Chrysophytes in Large Tributaries of Lake Baikal

Abstract High diversity of silica-scaled chrysophytes was recorded in the Barguzin River mouth and the Selenga River delta. Their flora was represented by 66 species and intra-specific taxa: Chrysosphaerella — 2, Paraphysomonas — 8, Clathromonas — 5, Spiniferomonas — 8, Mallomonas — 29, and Synura — 14. Eight taxa of silica-scaled chrysophytes were observed for the first time in Russia: Chrysosphaerella rotundata, Mallomonas doignonii, M. trummensis, M. corymbosa, Clathromonas poteriophora, Paraphysomonas acuminata acuminata, P. vulgaris, and Synura laticarina. In May, we found scales of Mallomonas striata with morphologically changed structure in the mouth of the Barguzin River and Srednyaya Channel of the Selenga River delta. The flora of silica-scaled chrysophytes studied differs from one tributary to another. We observed only 52 species in the Selenga River delta, whereas in the Barguzin River mouth we identified 35 species. These large rivers affect the flora of Lake Baikal diversifying silica-scaled chrysophytes in its southern and central basins. The total list of species and intra-specific taxa in the Selenga River delta, Barguzin River mouth, and in Lake Baikal includes 72 taxa. Therefore, this area may be considered as a “hotspot” of silica-scaled chrysophytes together with three hotspots observed worldwide earlier.

The status of the aquatic ecosystem of the Selenga river delta under long-duration low-water conditions

We examine the ecological aspects concerning the status of the surface waters in the delta of the Selenga river for the low-water conditions which have been observed since 1996. The ongoing changes in the most important indicators of the status of the waters in the river delta are assessed on the basis of results of hydrological, hydrochemical and hydrobiological investigations made by these authors in 2013–2015 and with consideration for earlier research efforts. It is established that the low-water conditions resulted in a decrease of the role of the main delta branches, Kharauz and Levoberezhnaya, in streamflow. An increase in the contribution of groundwater in the alimentation of the river led to an increase in concentrations of main ions: for the current low-water period their total content has varied from 119 to 780 mg/L, with a maximum in small delta branches in the wintertime. Changes in concentrations of biogenic elements were recorded: total phosphorus from 10 to 190 μg P/L, mineral phosphorus from 0 to 35 μg P/L, and nitrate nitrogen from 0.01 to 0.81 μg N/L. A minimum of mineral phosphorus compounds and nitrogen was observed at the time of mass development of algae. It is established that the dynamics of organic matter content is determined by changes in hydraulicity, and by the intensity of phytoplankton development. Within the long-term context, a deterioration of water regime and vegetation infill and swamping of shallow delta branches were recorded. The development level of the phytoplankton and changes in its structure point to a progressive eutrophication of the Selenga waters. According to the value of the saprobic index, the quality of the Selenga waters corresponds largely to the category of “moderately polluted” waters (class II and III), and it decreases at low-water periods, especially in shallow delta branches with a high population of cryptophytic algae, to the category of “polluted” waters.