Characterization of production/destruction processes in the Uda and Usalgin estuaries of the Sea of Okhotsk during the summer flood. P.Yu. SEMKIN, P.P. TISHCHENKO, P.Ya. TISHCHENKO, G.Yu. PAVLOVA, S.G. SAGALAEV, N.D. KHODORENKO, E.M. SHKIRNIKOVA,

Abstract

Characterization of production/destruction processes in the Uda and Usalgin estuaries of the Sea of Okhotsk during the summer flood. P.Yu. SEMKIN, P.P. TISHCHENKO, P.Ya. TISHCHENKO, G.Yu. PAVLOVA, S.G. SAGALAEV, N.D. KHODORENKO, E.M. SHKIRNIKOVA, M.G. SHVETSOVA (V.I. Il’ichev Pacific Oceanological Institute, FEB RAS, Vladivostok).

Parameters showing the direction of the processes of production / destruction of organic matter of the estuarine ecosystems of the Uda and Usalgin rivers with a flow rate of 4,390 and 173 m³/s, respectively, during the summer flood of 2016 are discussed. The estuaries of the Uda and Usalgin rivers are macro-tidal with tidal heights of up to 9.7 m. Tides break vertical density stratification of water. The concentrations of inorganic forms of nitrogen in river waters are low. These two factors reduce the intensity of autotrophic production in estuaries. However, high concentrations of dissolved organic carbon in river waters provide favorable conditions for heterotrophic production not only in rivers, but also in mixing zones. The source of inorganic forms of nutrients is the result of distraction of organic matter supplied by rivers, but this source, which is the basis of autotrophic products, is to a greater extent at the late stage of mixing zones with water salinity of more than 24 ‰. In general, estuaries of these rivers can be characterized as heterotrophic basins.