SOME INFORMATION ON HYDROLOGICAL AND HYDROCHEMICAL REGIME OF THE DAGESTAN SECTOR OF CASPIAN SEA

Aim. The paper assesses the chemical bases of biological productivity of the Dagestan sector of the Caspian Sea in terms of increasing the Volga runoff and sea transgression. The aim of this paper is to reveal the data on the spatial distribution and seasonal dynamics of some hydrological and hydro-chemical parameters. Materials and methods. Material for the study was collected with bathometer of Nansen in spring and summer during routine monitoring activities in the waters of the Dagestan sector of the Caspian Sea. Determination of hydrological and hydrochemical elements was carried out according to the "Guidelines for Maritime and hydrochemical research." Results. In summer, surface water temperature ranged from 22.9 to 25,9˚C, in spring, the average temperature was 17˚C. Temperature rise was observed on the horizon of 20.0 35,0m and was 5,1˚C in spring and in summer the temperature rose up to 8,2˚C. The vertical temperature changes were characterized by a decrease with depth. The greatest seasonal temperature gradients were recorded in the Northern Zone. Salinity has been characterized by spatial heterogeneity due to the uneven distribution of river waters. Lowest salinity has been recorded in the area of the mouth of Terek river, the highest in the southern part of the water area. Seasonal fluctuations in salinity in the surveyed area were insignificant and amounted 0,02 ‰. The vertical distribution of oxygen in the surveyed area was high throughout the water column. The pH value of the water area has increased as a result of the active photosynthetic activity of phytoplankton and increased from north to south from 8.12 / 8.05 to 8.45 / 8.53 in the spring / summer seasons, respectively. The distribution of phosphates in the water area was uneven and depended on the influx of continental waters and the degree of eutrophication. Because of the active photosynthetic activity of phytoplankton, the nitrates in the upper layer were almost absent. The average concentration of nitrates was 0.08 in spring and in summer – 19μg/l. Nitrites in surface horizons were completely absent. Nitrates could only be detected in small amounts in areas exposed to the river flow at a depth of 10m. Thus low average indicators (0,05 μg/l) could be marked on top of 10meter horizon. Conclusions. In the analyzed period in the waters of the Dagestan sector of the Caspian Sea favorable ecological conditions has been created for aquatic organisms, thereby increasing the biological production of the Caspian Sea. 

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