Étude de la phénologie de la reproduction de la Rhodophyceae <i>Palmaria palmata</i> le long des côtes françaises de la Manche

International audiencePhenological study of the reproduction of the Rhodophyceae Palmaria palmata along the French coast of the English Channel. In the rocky, intertidal level of the North Atlantic coast, Palmaria palmata is in terms of biomass, one of the most important Rhodophyceae. This economically interesting seaweed is harvested for several applications, and it is therefore important to evaluate algae stocks and to study population dynamics. Hence, a phenological study of four popu- lations of P. palmata was undertaken along the french coast of the English Channel. We were able to establish that some sporophytic and male gametophytic plants were fertile in fall and winter, while the majority of plants remained sterile during the whole year. Data have shown wide variations between the three sites studied regarding timing and the capacity of annual reproduction. Thallus fertility occurs earlier in the Western part of the English Channel than in the Eastern part, which could be explained by the differing water temperature gradient. The annual reproduction capacity is high at Roscoff, medium at Cap Lévy and weak at St Aubin