No 1 (2018)

This work is about the history and the main stages of the hydrochemical studies in Lake Baikal for the last 90 years. The first studies of Baikal water chemistry, including its deep-water zone, had been carried out at the late 1920s under the guidance of G. Yu. Vereshchagin. At the same time, the guide that was used during many years by chemical hydrologists for water chemistry analyses not only on Baikal had been developed. The long-term hydrochemical research of 1950s-1960s gave data on background concentrations of chemical components both in the lake and in its tributaries. The nowadays data evidence that the content of major ions in the deep-water zone of Lake Baikal is constant. It is found that the temporal and space changes of nutrients concentrations in the pelagic zone of the lake depend mainly on phytoplankton growth, whereas the current increase of nutrients concentrations in the littoral is mainly induced by human activities and the development of tourism.

It is found that the Selenga River, the largest tributary of the lake, undergoes the highest anthropogenic load. The pollutants, which enter the river in Mongolia, affect the content of major ions, nutrients and organic matter on the territory of Russia up to the mouth; more pollutants are added by Russian local wastewater sources. Amid the ongoing low water levels and increased anthropogenic load, the annual average concentrations of mineral phosphorous in the Selenga River show a trend to decline, whilst the content of phosphorous organic compounds increases. The efflux of mineral and total phosphorous by the Selenga is governed by changes of the water runoff. Changes in chemical composition of low-mineralized rivers of South Baikal (Khara-Murin and Pereemnaya) whose water catchment areas were affected for many years by emission of the Baikal Pulp and Paper Mill and by transfer of pollutants from the industrial complexes of Pribaikalye are registered.

We have shown the changes in the ecosystem of Lake Onego¹ with climate warming over the past 30 years. Due to climate warming in winter, the river runoff increases, as well as the flow of allochtonic substances into the lake. With the increased runoff of the Shuya River, the main tributary of the Petrozavodskaya Guba (Bay), there is an additional influx of iron and phosphorus to the lake combined with the humus substances. Deep-water benthic communities in the lake become depressed. Therefore, in the past three decades the role of climate warming in the aquatic ecosystem has increased in comparison with anthropogenic impacts, which differs significantly from the changes in previous decades.

Promising areas of ichthyologic research in Lake Baikal have been examined. Particular attention is being paid to the technology of remote fish census, including hydroacoustic methods and the method of quantitative environmental DNA analysis. These technologies may provide information on the status of artificially reproducible populations in reservoirs for developing a proper fishing strategy. The areas of application of molecular genetic methods for solving applied problems in creating the biological bases of fisheries, studying diseases, associated microflora and parasitic fauna, as well as for identifying fish feed objects have been determined. Studies aimed at restoring and maintaining the populations of rare and endangered fish species using artificial reproduction methods, including breeding, hybridization, hormonal stimulation of spawning producers, cryopreservation of sexual products, individual tagging, etc., are discussed. Prospects of mobile remote underwater video monitoring systems, the EthoStudio software package and the holography method to simulate sensory reaction in studying mechanisms of adaptations of fish in natural environment and to develop criteria for assessing their stability in aquaculture conditionshave been reviewed. Combining ethological studies and in-depth integrated morphological, molecular-genetic and physiological-biochemical screening of Baikal fish that would allow to better understand fundamental evolutionary processes responsible for the formation of behavioral adaptations, creation and maintenance of genetic diversity within and between populations in the natural environment, as well as developing recommendations on the introduction of state-of-the-art scientific monitoring approaches into aquaculture are very promising.

In recent years, significant changes in the ecological system of the coastal (littoral) zone, including mass death of the endemic representatives of the freshwater sponges of the Lubomirskiidae family, have been an urgent problem of Lake Baikal. Similar problems are known all over the world. Thus, mass disease and death of corals and sponges are indicated in the Mediterranean, Adriatic, Caribbean and other seas, which raises serious concerns about the future of these biocenoses (Olson et al., 2006; Webster, 2007; Wulff et al., 2007; Stabili et al., 2012). In Baikal, diseased sponges were first found in 2011. The area of sponge disease is constantly expanding, and, to date, dying specimens have been found throughout the lake. The mass death of sponges occur in presence of the large-scale violation of the spatial distribution and the structure of phytocenoses in the littoral zone, but the causes of these phenomena are unknown.

The relevance of the problem arises from the fact that changes in the littoral zone of Lake Baikal can significantly affect the productivity and composition of planktonic organisms and zoobenthos, which are the food base for fish, as well as the quality of drinking water. The deterioration of the ecological state also affects the attractiveness of the lake for tourism. At the international level, serious intellectual and financial resources were mobilized to solve similar problems. Despite the obvious relevance, in Russia such studies are carried out irregularly by small groups of researchers.

The results of long-term studies (1995-2017) of the physical properties and chemical composition of atmospheric aerosol in the Baikal region are considered. These studies are important for understanding the role of the atmosphere in the formation of the chemical composition and quality of the waters of Baikal and its inflows. Over the past two decades, Limnological Institute SB RAS (Irkutsk, Russia) have conducted various joint studies of the characteristics of atmospheric aerosol with Russian and foreign groups. The chemical composition, biological component, size distribution, spatial distribution and aerosol sources over the lake were investigated. The interannual variability of the main chemical compounds in the aerosol was estimated. So, over the period studied, there was a gradual decrease observed in the concentrations of the main ions in the aerosol composition: in Irkutsk by 2.1 times, Listvyanka - by 4.0 times, at the background site of Mondy - by 3.5 times. In addition to quantitative changes, there is a change in the ratio of the main ions in the aerosol at Listvyanka site (south-west coast of Lake Baikal) and at the background site of Mondy. Upon condition of no external influences the content of the main ions in the aerosol on the surface layer of Lake Baikal is significantly lower (0.33-5.2 μg·m^-3) than during of extreme conditions (2.2-5.2 μg·m^-3). Forest fires near Baikal cause an increase of the concentrations of Na⁺, K⁺, NH₄⁺, Cl^-, and NO₃^- ions in Baikal aerosols. Components of soil-erosion origin (Al, Fe, Zn, Cr, Ba) dominate in the elemental composition of the aerosol. Their concentration increases during forest fires up to 1.4 - 6 times at average. The flows of sulfur and nitrogen, the main acidifying components, differ in different years of observations both at the monitoring sites and over the surface of Lake Baikal.

Undoubtedly, the study of the Planet’s climate is one of the fundamental topics for elaboration of strategies for life support of the Earth’s population. The following questions arise: i) what is the spatial pattern of intensity of these changes; ii) what is the response of the regions to climatic changes; iii) what is the critical line when changes in the ecosystem are irreversible; iv) what are causes and mechanisms of these changes; v) what is the human role in these processes; and vi) which tendencies should be expected in climate changes in the nearest future? After answering these questions, a logical question is put forward: how unique is “the climatic landscape” of the recent decades compared to the previous epochs, and are all regions similarly sensitive to climatic changes? The challenge is how to describe these changes and which methods to use in order to obtain more reliable data. More generally and despite some problems, the studies indicate the value of combining limnological and palaeolimnological records in reconstructing lake history and in disentangling the changing role of different pressures on lake ecosystems.

Environmental DNA (eDNA) analysis is a powerful tool for detecting aquatic animals. Numerous studies have shown the high efficiency of the eDNA methods for the detection of species that are difficult to identify using traditional approaches. Other studies have demonstrated the high usefulness of eDNA for studies of species communities and species abundance. Here, we briefly describe the advantages of this method in relation to studying the biodiversity of the ecosystem of Lake Baikal. Traditional methods of biodiversity monitoring have a number of limitations here due to a great depth of the lake and a large number of rare endemic species, which occupy limited habitats, often in the deep-water zone. Using eDNA will overcome this limitation. It can fundamentally change the understanding and assessment of the biodiversity of Lake Baikal and solve other scientific and environmental problems in the region.

Limnological data on the coastal zone of the world’s greatest lakes are scanty in contrast to the deep-water research that is actually the main reason for a delayed response of the researchers’ and public community to evident anthropogenic changes the lake ecosystems are experiencing worldwide. The present study reports on the interdisciplinary investigations in the coastal zone of Lake Baikal during 2000–2018 and gives a brief description of the splash zone as a principal part of the lake ecosystem poorly known in other lakes of the Planet so far. Recent surveys of Lake Baikal showed a key role of the coastal zone research for the fundamental limnology and efficient monitoring of the lacustrine ecosystems. The splash zone of Baikal is briefly described due to its peculiarity. Principal reasons of significance of lake coastal zone research such as: maximal biodiversity of lacustrine ecosystems, high macrobenthos productivity in Baikal, intensive biogeochemical processes in rift and karst lakes and their reasoning are described. This is the zone that first of all colonized by invasive species and where the obvious cyclicity in plankton-benthos relationships is clearly expressed. Early warning signs for the ecological disturbance, such as blooms and wash-ups of native and/or alien algae, degradation of pelagic and benthic communities, bioaccumulation of pollutants (including organochlorine compounds) by hydrobionts, etc. are manifested in the coastal zone. A short report of the current ecological crisis in the coastal zone by 2018 is presented. The uniqueness of Lake Baikal makes the ongoing eutrophication different from all other Palearctic lakes. Therefore, the hydrochemical indicators of the water column of great lakes do not match the commonly accepted principal eutrophication criteria pool. Biological indication approach appears most appropriate for the analysis of the initial eutrophication stages. The author points out real and potential sources of excessive biogenic element supply into the lake ecosystem such as, sewage contamination of the estuarine parts of Baikal tributaries by the coastal settlements and vessels, pollution of the ground and interstitial waters of the beaches, input of biogenic elements as a result of mass mortality of sponges and other hydrobionts, secondary contamination by decaying algal wash-ups, intensive nutrient influx after numerous forest fires on the lake coasts and aerosol contamination. All these factors provide new opportunities to evaluate the initial eutrophication stages either on Baikal or in any other of the giant lakes. Special emphasis is given to an inadequate governmental lake monitoring systems focusing on the pelagial zone without taking into consideration the coastal (splash zone included) biological communities. Our landscape-ecological method served a basis for elaborating approaches for complex monitoring of Baikal coastal zone recommended as a part of the Federal Baikal Ecosystem Monitoring.