Évolution des peuplements macrophytobenthiques le long d'un gradient d'eutrophisation (Golfe de Maliakos, Mer Égée, Grèce)

The phytobenthos of five stations of the Maliakos Gulf, situated along an eutrophication gradient, comprises 186 taxa, which corresponds to the number of species found in similar gulfs on the Creek coasts. Samplings concerned three types of algal communities: 1) reference communities (in open sea) unaffected by euhophication: 2) modified algal communities in the most polluted and ecologically instable area (catastrophic events); 3) intermediate communities. Rhodophyceae are qualitatively dominant (number of species) in all stations. In the most polluted stations, Ulvophyceae are quantitatively dominant (cover), while Fucophyceae are quantitatively dominant in the non-polluted stations. The ratio Quantitative Dominance/Qualitative Dominance (Tension) of different taxonomic groups appears as a good ecological descriptor. This is not the case of the Diversity index, which presents equal values in the most polluted stations and in the reference ones.