Zooplancton et micronecton estivaux des deux cents premiers mètres en Méditerranée Occidentale

The specific and quantitative distribution of zooplankton and micronekton sampled during the R.V. “Jean Charcot” Polymed cruise (Western Mediterranean Sea, May/June 1970) in the superficial layer (0 to 200 m) is explained in relation to the environmental characteristics. The biomass increase of this layer at night is great for micronekton (1×10) and low for macroplankton (1×2). Diurnal mesoplankton migrations can be disregarded. The macroplankton shows no peculiarity in geographical distribution. For the micronekton, the biggest concentrations of fishes (in the Alboran Sea) seem to be related to the Atlantic Current; on the other hand, euphausiids are more numerous to the north of the 40th parallel, especially in the Gulf of Genova. Quantity and species characteristics of the mesoplanctonic populations are connected with the Atlantic Current and divergences.