Écologie d'un milieu eutrophique: traitement mathématique des données

Numerous data on physical, chemical and biological parameters in the dilution layer of the Rhône mouth have been studied by multivariate techniques: principal-component analysis, part correlation. A new technique of cluster analysis is also proposed. By these means, a very euryhaline group of zooplankton species has been isolated and the extremely low sensibility of phytoplankton towards salinity has been shown. However, temperature seems to be the most important ecological factor. Instability and eutrophy of this area do not appear to disturb the phytoplankton cycle, which occurs with its usual succession. Chlorophyll a and organic matter do not seem of value for estimation of the biomass in the area studied.