Distribution and morphological variation of low-shore algal turfs

Abstract

The distribution of three functional groups of algae (filamentous, corticated terete and calcareous articulated) was investigated in low-shore, turf-forming assemblages from rocky shores in the western Mediterranean Sea (Italy). Algae were sampled along shores from three different stations. Shores were either exposed to wave action or sheltered and were characterised by various inclinations of the rocky substratum (horizontal, sloping and vertical). The hypotheses tested were: that the relative abundance of the three functional groups of algae (1) varies between sheltered and exposed shores, (2) is influenced by substratum inclination and (3) that these distributions are consistent across stations. There was no clear relationship between the morphology of turf-forming algae and shore characteristics. Covers of filamentous, corticated terete and calcareous articulated algae differed among shores and stations, but patterns were not consistent across shores with similar exposure to waves and substratum inclination. Turfs often comprised algae with different morphologies, in a combination of anchor and epiphytic species. It is suggested that functional groups of algae, as currently identified, are not effective in describing changes in distribution of algae between sheltered and exposed shores, when turf morphologies are considered. Future research on relationships between morphology and ecology of algae should consider the potential importance of positive interactions among associated species, which could override responses of individual functional groups.