Environmental Control of the Mesoscale Distribution of Primary Producers and its Bearing to Primary Production in the Western Mediterranean

Abstract

The Mediterranean has often been called as a small-scale model of an ocean. Indeed it offers the possibility to study selected phenomena in another dimension. Size is important, as it limits the windows of energy input. A larger ocean allows for a wider spectrum of inputs and much higher local intensities. Tides and anticyclonic gyres are not important in our sea. The Mediterranean has properties of its own: It can be considered as a two-layered, inverse estuary opening into the Atlantic; exchange of water with the Atlantic, in each direction is about 70 times the excessive evaporation that drives it. One consequence is the oligotrophy of the Mediterranean. An oligotrophic system is a good reagent to test consequences of fertilization, providing an ideal place for a detailed analysis of control of primary production. The Mediterranean has a unique feature in the winter mixing in the Gulf of Lions that reaches to extraordinary depths. The annual thermal excursion of surface waters is very large; the thermal cycle controls the density of surface waters and the basic features of the annual biological cycle