The model of eutrophication of marine and estuarine ecosystems in the northwest Black Sea Region

Abstract

The paper outlines the mathematical structure of the numerical mathematical model of water eutrophication. The model is based on the numerical non-stationary hydrothermodynamic model MECCA (Model for Estuarine and Coastal Circulation Assessment) supplemented with a chemical-biological modular unit designed in accordance with the principles of preparation of the water quality model RCA-HydroQual with some modifications introduced by the author. The chemical-biological unit of the model includes a description of the dynamics of the following hydroecological variables at a local point of space: biomass of phytoplankton, mineralization-resistant organic phosphorus in suspended (detrital) and dissolved fractions, labile organic phosphorus in suspended and dissolved fractions, dissolved mineral phosphorus, stable organic nitrogen in suspended and dissolved fractions, labile organic nitrogen in suspended and dissolved fractions, ammonium and nitrate nitrogen, suspended and dissolved fractions of organic carbon resistant to biochemical oxidation, suspended and dissolved fractions of labile organic carbon and water-dissolved oxygen. The paper presents results of calibration and verification of 1D version of the model for the case of the Tyligulskiy Liman (Estuary) in the northwestern part of the Black Sea. A conclusion is drawn that the model makes it possible to display the main features of the annual dynamics of hydroecological characteristics of the liman during phytoplankton vegetation season, in particular, the conditions determining the processes of primary production and biochemical oxidation of organic substance, regeneration of mineral forms of biogenic elements. Application of the model in order to assess the impact of deepening the ‘liman-sea’ connecting canal on the hydroecological characteristics of the Tyligulskiy Liman proved that intensification of water exchange with the sea through the canal will help to reduce phytoplankton production, concentration of organic substance in the water of the liman and, ultimately, will lead to improvement of its trophic status. The model is expected to be further used to assess the effectiveness of various scenarios of managing the hydroecological regime of the limans of the north-western Black Sea region considering the changes of climatic conditions.