1-D coupled physical-biological model of the northwestern Mediterranean Sea

A 1-D coupled physical biological model of the ecosystem of the Ligurian Sea is described. The physical model has been adapted from a thermal dispersive lake model (Tassin, 1986), and the biological model from the sub-models AQUAPHY (Lancelot et al., 1991a) and H.S.B. (Billen and Servais, 1989). The biological model considers two types of phytoplankton, diatoms and nonsiliceous flagellates, to describe the response of the phytoplankton community and the related food-web to different types of fertilization (by river, atmospheric deposition or deep water upwelling) with different N:Si ratios. This distinction, and the detailed description of the microbial loop, helps to distinguish between new and regenerated primary production. The model has been calibrated on FRONTAL 1986 data, obtained monthly at a long-term station (43°24'N, 07°52'E). The quantitative biomass, its repartition between diatoms and flagellates, and its spatio-temporal variability are reasonably well reproduced by the model. From these simulations, an annual new production of 62 g C m^-2 is computed, contributing 35% of total annual primary production (180 g C m^-2). This calculation reflects the oligotrophic state of the system, where regenerated production occurs most of the year while the biomass remains low. A Monte-Carlo sensitivity analysis performed on the parameters driving the model leads to a confidence interval for the simulation and also to a better understanding of how the model functions.