An Intertidal Zone with 13m of Tidal Amplitude and a Tideless Sea

the Atlantic and Mediterranean Coasts of France

Abstract

The vertical distribution pattern of rocky shore organisms was studied along two French coasts, at Marseille with no true intertidal and in Brittany with a large tidal amplitude of 9 -13m at spring tide. A marked zonation pattern was recognized on both shores and photographs of some of the common animals and plants are presented. At Marseille, the supralittoral zone was characterized by the periwinkle Melaraphe neritoides, which was also abundant in the upper mediolittoral zone characterized by the barnacle Chthamalus stellatus. Growths of the calcareous alga Lithophyllum tortuosum were conspicuous in the lower mediolittoral zone of exposed shores. Beds of the mussel Mytilus galloprovincialis developed around the upper fringe of the infralittoral zone and harbored many small animals, mainly amphipods, polychaetes and mollusks. Habitat segregation was recog-nized between closely related species, e.g. between Hyale spp. and between the nereids Perinereis cultrifera and Platynereis dumerilli. Along the coast of Brittany, the zonation pattern of the inter-tidal animals and plants as reported by Lewis (1964) was found. However, in the vicinity of Dinard, the chthamalid found in the higher eulittoral zone was not Chthamalus stellatus but C. montagui. The facilities of four marine stations, “Station Marine d'Endoume”, “Laboratoire Arago”, “Station Biologique de Roscoff” and “Laboratoire Maritime de Dinard”, are also presented.