The influence of upwelling and entrainment on the algal bloom in the Baltic Sea

Hydrodynamic processes control many geochemical and ecological processes in the sea. In this paper, the influence of up- and downwelling and entrainme nt on the ecosystem components are studied. The ecohydrodynamic model was i nitially used to simulate the whole Baltic Sea to get the boundary conditio ns for the Gulf of Riga. Then, to study the influence of different hydrodyn amic conditions on the algal bloom, three simulations were made for the Gul f of Riga using different boundary and entrainment conditions. It appears t hat upwelling in the gulf was strongly dependent on open boundary condition s between the Baltic Proper and the gulf. The vertical transport in the Gul f of Riga was many times more intensive in the calculation system Baltic Pr oper and Gulf of Riga, than in the case where only the Gulf of Riga was sim ulated. The blue-green algal bloom was influenced by the vertical transport due to different nutrients' limitation mechanism. (C) 2000 Elsevier Scienc e B.V. All rights reserved.