Seston superficial de la zona de afloramiento del NW de Africa

SUR FACE SESTON OF THE UPWELLlNG AREA OF NW AFRICA. - A principal component analysis was appl ied to some 600 particle countings (made with a model TA Coulter) and to chlorophyll data obtained from the same samples of oceanic water from the upwelLing area of the NW Africa. Samples were taken (one every half an hour) and analyzed in the way between every two hydrographical stations, resulting in a mean separation between succesive samples of 3 or 4 miles. A simple cluster analysis was made on data issued from the principal component analysis in order to group samples. The results show that small particles ( between 6 and 14  µm) predominate in onshore waters (where upwelling centers are found) while larger particles ( between 22 and 45 µm) become more important in the offshore direction. Part icles with sizes between 10 and 25  µm of diameter are dominant in offshore waters, poor in both particulate material and chlorophyll .