ECOLOGICAL LIMITS TO THE INVASION OF SARGASSUM-MUTICUM IN NORTHERN SPAIN

In northern Spain Sargassum muticum is abundant on sheltered shores an d in tide pools on exposed shores, but is rare or absent at low-intert idal levels on exposed shores. An experiment on two shores indicated t hat S. muticum has an effective dispersal range of less than 5 m and t hat the presence of fertile plants in the immediate vicinity were requ ired for settlement of large numbers of S. muticum. Few recruits were recorded in quadrats with a canopy of turfing and foliose algae. The r esults suggest that the lack of free space and supply of propagules pl ay important roles in Limiting the invasion of S. muticum at an expose d shore in northern Spain. It therefore appears unlikely that S. mutic um will significantly disrupt the ecology of the low-intertidal level on exposed shores in northern Spain. (C) 1998 Elsevier Science B.V.