Phytoplankton variability in summer in the northwestern Mediterranean: Modelling of the wind and freshwater impacts

A coupling between a 3-D mesoscale hydrodynamic model and a biogeochemical model was performed in the northwestern Mediterranean to reproduce the majo r processes of carbon and nitrogen cycles involved in the new production of phytoplankton biomass. The study was focused on simulating the real condit ions of the EURHOGLI campaign, performed in summer in the Gulf of Lions (Ju ne-July 1983). Results of the coupled model showed the high variability of the Rhone river plume position and the associated phytoplankton biomass. Th e validation of the model was in good accordance with field measurements an d CZCS and AVHRR remote sensing pictures available at the period considered . In addition, results showed that the phytoplankton biomass induced by fre shwater nutrients was strongly controlled by the variability of the local w ind conditions. The model, performed with representative forcing conditions , allowed to better understand the representative phytoplankton features th at prevails in summer in the Gulf of Lions, where both strong winds and fre shwater runoffs interact.