Influence of fishing and functional group of algae on sea urchin control of algal communities in the eastern Atlantic

Abstract

We address the effect of several factors influencing the depth of interfaces between the shallow photophilic brown algal assemblages and Diadema antillarum urchin-dominated barrens on rocky reefs of the warm-temperate central-eastern Atlantic. By means of a multifactorial observa- tional approach, we hypothesized that it would be locally influenced by (1) the functional structure of the dominant brown algal assemblages (corticated foliose algae versus large frondose coarsely- branched fucoid species), in addition to (2) the fishing status (fished versus unfished sites) and (3) the large-scale topography of the substrate. Our results show that brown algal assemblages reach deeper waters at unfished sites, which is independent of the dominant brown algal functional group. How- ever, monospecific algal facies dominated by large frondose coarsely branched fucoid species (mainly the genera Cystoseira) reach deeper waters in comparison with corticated foliose algae, at fished sites.