Etude préliminaire des effets de la pollution globale sur le peuplement planctonique des ports Nord de Marseille

A preliminary study of hydrological and biological parameters has been undertaken on surface waters of the Northern Harbour of Marseilles, France. The present work is part of a broader research scheme relating to secondary zooplankton production in an environment half closed off from the sea. It represents a primary contribution to the exploration of halfclosed or closed marine spaces which come under the influence of pollution and eutrophic factors. The complexity of the harbour milieu is discussed, and the basic problems defined. The harbour waters are characterized by high concentrations of seston; this parameter enables a delimitation dividing polluted waters from the Marseilles Gulf waters to be determined. Other hydrological parameters, although of more complex nature, may also help, in some cases, in characterizing harbour waters. High temperory concentrations of characteristic holoplankton species, which seem to find here their preferred biotope, divide the harbour milieu from the open waters of the Gulf, as do other meroplanktonic or semi-benthic species. Finally, the half-closed milieu studied here provides, for particular periods and under conditions still to be specified, a eutrophic milieu which promotes intensive growth of zooplankton and phytoplankton.