Mediterranean sea trophic characteristics interpreted through three-dimensional coupled ecohydrodynmaical models

摘要

The spatial variability of the Mediterranean ecosystem in response to the variability in nutrient supply and demand is addressed through basin-wide aggregated ecological hydrodynmaical coupled models. A discussion of a multi-nutrient two-phytoplankton ecosystem submodel is presented togethe rwith a more aggregated implementation including dissolved inorganic nitrogen, phytoplankton and detritus. This modelling effort gives an interpretation of the nutrients gradients in terms of the effects of the interplay between both biological and dynamical processes. The general oligotrophy of the Mediterranean Sea is in principle explained by the inverse estuarine circulation. Three elements in particular seem to be relevant in creating the North-South and East-West gradients: the different physiogrphy of the two subbasins, the detrital fall-out from the ertile zone and hte cyclonic and anticyclonic wind driven structures. The vertical fluxes of biogenic material and the nutrient exchanges at the bottom of the euphotic zone seem to play an important role in modifying the N:P ratio at depth along the east-west axis.