modeling approach of the Ross Sea plankton ecosystem

A conceptual and numerical model adapted to the local plankton ecosystem (ECOHYDROMVG) has been developed on the basis of the information acquired during various oceanographic cruises in the Ross Sea. The construction of the biological/physical coupled 1-D model of the upper water column ecosystem is presented. The model takes into account the control of the plankton ecosystem by ice cover, ice edge dynamics, atmospheric forcing and surface circulation, nutrients being non-limiting factors. Ice-edge thickness, retreat and melting determine the initial conditions for the spring bloom (ice algae concentration, vertical structure of the water column) and allow the biological processes of primary production in the water column to start. The combined effects of wind and solar irradiance determine the depth of the upper mixed layer and quantitatively control photosynthetic levels. In this approach, biological variables are limited to diatoms, Phaeocystis and smaller cells, depending on local conditions. Grazing activity forcing by Euphausia superba, copepods, Limacina helicina and amphipods control the phytoplankton variables. The model is used to determine a standard state of the Ross Sea plankton ecosystem and numerical results accurately simulate the vertical stabilization of the water column within the Ross Sea marginal ice zones during the ice-melting period, and the biological structure of the upper layers. It simulates primary production and the selection of the type of phyto- and zooplankton communities. It is applied to local situations controlled by different wind conditions, ice cover and initial content of ice algae, and accurately reproduces field observations