Long-term variability in the hydrochemical regime of the Manych-Chograi hydrological system

Data collected from the scientific literature and field studies carried out by the specialists from the Azov Branch of the Murmansk Institute of Marine Biology and from the Southern Scientific Center in July and August of 2004 are used to confirm the further salinization of the Manych-Gudilo Lake. The aforesaid salinization was accompanied by a change in the water state index, caused by an increase in the salinity of inflowing water, which determines the water-and-salt budget of the lake.     

Impact of atmospheric circulation fluctuations on the zoobenthos dynamics in the Sea of Azov

The impact of atmospheric circulation fluctuations (Vangengeim’s classification) on the zoobenthos dynamics in the Sea of Azov was studied. The “western” circulation processes lead to zoobenthos biomass decrease, and the opposite pattern was observed when “eastern” circulation processes prevail. A quasiperiodicity with 3–7 to 10–15 year cycles is revealed for the zoobenthos biomass dynamics. These changes are closely connected with the climatically induced increase of the zoobenthos biomass in the Sea of Azov.     

Current Desalination of the Sea of Azov and Its Correlation with Long-Term Variations in Atmospheric Circulation

Correlation is established between the long-term variations in the frequency of the atmospheric circulation forms, water balance elements, and the Sea of Azov water salinity. It is found that the river runoff into the sea and the sea freshwater balance increase and the sea salinity decreases in the periods, when northern and western forms of atmospheric processes develop; in the periods with a greater frequency of the eastern type of atmospheric macroprocesses, the situation is reverse. It is also found that the effect of atmospheric circulation on the sea salinity tends to strengthen, whereas the effect of the human-induced decrease in river runoff tends to diminish. The current desalination of the Sea of Azov down to 10.5 is shown to be mainly due to the development of western and northern forms of atmospheric circulation in the cold season of a year during the last 10–15 years.     

Present-Day Estimates of the Hydrological Conditions for the Formation of Biological Production in the Sea of Azov

The main feature of the present-day hydrological conditions governing the formation of biological production in the Sea of Azov is shown to be the appreciable freshening of seawater, which is due, first of all, to climate changes. It is established that the freshening of seawater can benefit most for the reproduction of fish resources in the Sea of Azov only if the river runoff withdrawals are reduced step by step down to 5 km³/year (14% of the norm), the annual runoff is maintained at 35–36 km³, and the spring runoff is restored to 18.5 km³.     

Climatic changes in zoobenthos of the Sea of Azov under anthropogenic impact

The relationship between many-year variations in zoobentbos of the Sea of Azov and the largescale variations in atmospheric circulation (G.Ya. Vangengeim typification) from the mid-XX to the early XXI century has been considered. It has been shown that the western form facilitates an increase in zoobentbos biomass of the Sea of Azov and the eastern form, its growth. The effect of the northern type of macroprocesses is controversial. The change from eastern to western form in the mid-1980s caused a freshening in the Sea of Azov and reduced the total zoobentbos biomass, especially mollusk. The farther predominance of the western form will facilitate the preservation of the present-day structure of benthic communities up to the end of the first quarter of the XXI century.