Field of the Dissolved Organic Matter Content in the Taganrog Bay (the Sea of Azov)

Based on the actual and climatic oceanological data, the notions on composition of the field of the dissolved organic matter content in the Taganrog Bay, from the Don River mouth to the Azov Sea adjacent water areas are obtained. The features of the natural marginal filter of the Don mouth and the runoff waters in the bay are considered. Significant heterogeneity in the field of the considered characteristic (its concentration exceeds the natural standard in the Don mouth) is revealed, that can probably be a consequence of the dissolved organic matter anthropogenic sources, in other words, waste waters from the settlements. The pronounced frontal section, i. e. a natural marginal filter, was revealed in the field of the dissolved organic matter concentration. It was located along the maritime part of the Don River mouth within the narrow shore strip (its width is approximately 0.5–1.0 miles). Across this natural marginal filter, the dissolved organic matter concentration reduced abruptly towards the open sea. Up to 50% of the dissolved organic matter brought to the marine part of the Don mouth remained on the filter. It is revealed that salinity and the dissolved organic matter content in the marginal filter area are closely bound by the backward correlation dependence with the coefficient -0.87. It is shown that the dissolved organic matter concentration in the Taganrog Bay decreases in the area between the marginal filter and the runoff front from 20 to 3 mg/l, and complete transformation of the bay waters saturated with the dissolved organic matter is observed in the runoff front which, in course of the major part of a year, is located at the bay outlet. Seaward off the front external boundary (isohaline 10 PSU), the fields of salinity and dissolved organic matter content are characterized by spatial homogeneity with the 10-13 PSU salinity and the dissolved organic matter concentration 1-3 mg/l which are typical of the Azov Sea open water areas. It is found that weakly pronounced vertical stratification of the field of the dissolved organic matter concentration is peculiar to all the studied water areas.