Vol 46, No 5 (2019)

An intergovernmental group of experts on climate control obtained the forecast options of the dynamics for the weather components of the Ob-Irtysh river basin in the XXI century for four global climatic scenarios of the family “Special Report on Emissions Scenarios” complying with the set scenarios of economic, technological, political, and demographic development of the civilization, which served as the basin for the estimation of the options of possible changes of the water balance components of the specified river basic up to the middle of the XXI century. The calculation technique is based on using the physically based model of heat and mass exchange between the land surface and atmosphere SWAP and the climatic scenarios generator MAGICC/SCENGEN. The changes of the annual flow of the Ob river due to potential global climate changes were compared herein with its natural fluctuations caused by the weather noise.

The analysis of the reliability of different scenarios for the formation of the vertical structure of the waters of the Caspian Sea, obtained from the distribution of transient tracers (CFC-11, CFC-12, ³H and ³He) at the deep-water stations of the Middle and Southern Caspian within the framework of international integrated isotope-geochemical studies during the maximum sea level rise in 1995–1996. Taking into account the available hydrometeorological data and the characteristics of water dating using transient tracers, it was concluded that after large-scale gravitational convection in the Middle Caspian caused by anomalous cooling of surface waters in the Northern Caspian at the end of the winter of 1976, a structure of water masses was formed that excluded deep water ventilation in the Middle and South Caspian Sea until the mid-90s.

The analysis of observation data on fluctuations in the level and velocity of currents in the Petrozavodsk Bay of Lake Onega, performed in 2016–2017, was carried out. Level oscillations were measured with a discreteness of 10 s using two TDR-2050 devices (RBR Ltd., Canada). Spectral analysis was performed using the simple Fourier transform method after one-minute data averaging to reduce instrument noise. Energy-carrier periods corresponding to the seiches of Petrozavodsk Bay and the Lake Onega are identified. Current velocities were measured with Aquadopp HR-Profiler (Nortek, Norway). Within the framework of the linear long wave theory, seiche oscillations are considered in a model basin approximating the Petrozavodsk Bay with regard to the Ivanovskiye Islands. Using an analytical solution, estimates for the periods of the higher seiche modes and the corresponding maximum wave flow velocities are obtained for the Petrozavodsk Bay. The comparison of theoretical estimates with the data of field observations, was showed satisfactory agreement.

The results of the methane concentration distribution in different areas of Lake Baikal obtained in 2014 and 2015 were analyzed in this study. In periods of expedition examinations, the methane concentration in the water and in the bottom sediments of the lake varied in a range from <0.1 to 13.9 μl/dm³ (average: 0.7 μl/dm³) and from <0.01 to 3.69 μg/g of the dry deposition (average: 0.34 μg/g). The maximum methane concentrations in the water and bottom sediments in the lake were typical for the North region, where rivers Verkhnyaya Angara and Kichera are flowing, and in the individual stations of the profile set along the mouth area of the river Selenga, as well as the stations located in the zone of the waste water underwater release of Baikalsk City and the Baikalsk pulp and paper mill closed in 2013. The presence of increased and decreased methane concentrations in the examined top strata of the sediments of Lake Baikal was stipulated herein aside from the differences in the power of the anthropogenic effect by the variation of the sediment accumulation conditions determining the particle size distribution and the organic matter content and, as a result, by the methanogenesis intensity.

Sanitary-microbiological and hydrochemical research of rivers flowing into Baikal in the area of Lystvyanka settlement was carried out from 2014 to 2015. It was found out that water quality in the mouths of such rivers as Bolshaya Cheremshanka, Malaya Cheremshanka and Kamenushka fell out of the standards of normative technological document in Russia, as well as abroad (US and Europe) based on such indicators as thermotolerant coliform bacteria (TCB), thermotolerant E. coli, enterococci. The quality of water in the mouths of B. Cheremshanka, M. Cheremshanka, Kamenushka rivers was far from standards of the above mentioned (Russia) by hydrochemical indices such as phosphates (PO₄^3-). In June 2015, the standard by TCB group was exceeded more than 10 times in coastal water of Lake Baikal near B. Cheremshanka River mouth. Thus, the water quality sampled from the river mouths in comparison to river waters sampled above settlement was significantly poor. Moreover, in July 2015 when the number of tourists was maximal, high gradient between amount of fecal bacteria in river mouths compared to the water samples from the upstreams on background stations was found. To stop local damage of the ecosystem in Lystvyanka area the construction of wastewater treatment station here is urgent and reasonable.

The short-term, seasonal, and interannual variations in the abundance and species composition of the Black Sea metazoan microzooplankton have been analyzed at the open coastal area and the mouth of Sevastopol Bay in 2009–2015. Whatever the time scale, the temperature factor played the main role in abundance variations. In particular, the coincidence of two-year periodicities in the sum of active temperatures and the abundance of copepod-invader Oithona davisae at the interannual scale have been demonstrated. Variations of wind speed and direction have been shown to be significant factors in the short-term variations of microzooplankton abundance. The total species diversity of the community was found to depend significantly on the abundance of the invader species.