Influence des conditions hivernales sur les productions phyto-et zooplanctoniques en Méditerranée Nord-Occidentale. III. Caractérisation des eaux de surface au moyen de cultures d'algues

Bioassays were performed on surface-water samples, collected during the Médiprod I cruise of the R.V. "Jean Charcot" in the northern part of the Mediterranean Sea. Physiological responses of axenic algal cultures were measured in order to characterize the different water masses. The responses obtained are specific to each algal strain: Phaeodactylum tricornutum grows in all waters sampled during the first part of the cruise, while Chaetoceros lauderi does not develop because of its different nutritional requirements; Chlamydomonas magnusii does not grow in any of the tested samples. No clear relationship exists between the results obtained in vitro and those obtained in situ but, on the whole, the waters collected during the second part of the cruise allow a higher growth of the test algae in vitro. This higher fertility is probably related to the algal bloom which occurred between the first and the second part of the cruise. In the authors' opinion the great difference in uptake rates observed between the high-turbulence area (low production) and the adjacent area (high production), may be related more to biological conditioning than to any physical process. However, physical mixing seems to be responsible for inhibition of primary productivity at the two stations where mixing attains maximum values. © 1973 Springer-Verlag.