AN EXPERIMENTAL EVALUATION OF THE EFFECT OF WAVE ACTION ON THE DISTRIBUTION OF SARGASSUM-MUTICUM IN NORTHERN SPAIN

The invasive brown seaweed Sargassum muticum was first recorded in nor thern Spain in the 1980's. The species is now patchily distributed in localities that differ in wave-exposure and is most abundant in shelte red areas. A transplant experiment was done on a local scale to test t he ability of S. muticum to persist and grow on wave-exposed shores. O ne month after transplantation, plants moved to exposed areas suffered a high percentage of breakages (>80%). When only plants without damag e were considered, those transplanted to exposed areas exhibited a mea n elongation rate significantly less than those on the sheltered shore . The lower rate of elongation in the absence of any apparent injury s uggests a grade of phenotypic response of S. muticum to changes in the physical conditions. Nevertheless, the low tolerance exhibited by thi s species to mechanical stress indicates that its distribution may be limited by physical conditions in wave-exposed environments.