Ecology of Sargassum muticum (Phaeophyta) on the North Coast of Spain: IV. Sequence of Colonization on a Shore

Abstract

The sequence of intertidal colonization by Sargassum muticum at Aramar Beach (North of Spain) was studied during three years following its first recorded appearance. Only two plants were found in a low-shore intertidal rockpool in the first year. The following year mid-shore and low-shore intertidal rockpools were colonized but only a few plants were attached to low intertidal rocks. During the third year plants covered all available intertidal substrata between 0.0–0.4 m above L.A.T. as well as the related rockpools. Differences in percent cover, size of primary lateral branches, density and reproduction were significant between tidal levels and habitats although mortality of recruits was similar (close to 95% at all tidal levels). The low intertidal, with ample free space available, was the main site of attachment after the first two years of colonization. The seasonal cycle of growth and reproduction showed differences in relation to the tidal level, with a shorter period of growth and reproduction as well as a longer dormancy period at mid-shore rockpools. A conceptual model for the spreading of S. muticum at Aramar is also proposed.