RECONNAISSANCE OF THE MAIN BLACK-SEA ECOHYDRODYNAMICS BY MEANS OF A 3D INTERDISCIPLINARY MODEL

A 3D interdisciplinary model has been used to test the sensitivity of the Black Sea's ecosystem to physical processes. The hydrodynamical mo del of the general circulation has been built up, using the GHER primi tive equation model. A model with 15 km horizontal resolution and 25 v ertical levels is used to compute the typical seasonal cycle. The mode l is forced by climatological monthly mean fields of temperature, sali nity and wind stress at the air-sea interface; the river discharges of the Danube, Dnestr and Dnepr are taken into account. An ecosystem mod el at basin scale is then defined by a nitrogen cycle considering seve ral phytoplankton and zooplankton sizes and including the microbial lo op. The ecosystem model is embedded on-line into the 3D hydrodynamical model with a superimposed cycle for the light intensity. This model m ust be regarded rather as a first tool for testing the coupling of hyd rodynamic and ecosystem submodels, while acquiring some preparatory as sessment of the effect of physical processes on the ecodynamics. The r esults display a highly three-dimensional aspect with important horizo ntal and vertical variations, obviously imparted to the system by the physical processes (horizontal and vertical advection, vertical mixing and diffusion, upwelling...) associated with light limitation at dept h and sinking of dead organisms. In this paper, the results are descri bed emphasizing the effects of the hydrodynamic constraints on the spa ce-time distribution of the primary and secondary production. (C) 1998 Elsevier Science B.V. All rights reserved.