Influence of Small Rivers' Runoff on the Hydrochemical Structure of Coastal Waters of the North-Eastern Black Sea

River runoff is the main source of nutrients and man-made pollutants that affects functioning of biological communities. About a thousand small and medium rivers flow into the Black Sea, and while their contribution in total sea balance is significant, there are no systematic observations on that matter. This work presents the studies carried out in 2006–2010 in coastal area of the north-eastern Black Sea. Attention is focused on studies in 2009 near the Greater Sochi region, since two major local rivers, Kudepsta and Mzymta, significantly differ in composition, which allows tracing the inflow of each individual river and estimating their fractional contribution to formation of surface water structure. Influence of river runoff on hydrochemical balance of nearshore water is demonstrated, with estimations of amount of dissolved carbon, alkalinity, silicate, dissolved oxygen and pH. Development of the river plume is traced, along with its reaction on wind direction and shelf circulations.