Ecological dominance of Lessonia nigrescens (Phaeophyta) in central Chile

Abstract

Experimental removal of various types of dominant canopies has resulted in predictable patterns of competitive hierarchies among algae in intertidal and subtidal communities. Few attempts were made to distinguish functionally different groups of algae in these communities. The intertidal/subtidal boundary of exposed rocky habitats in central Chile is numerically dominated by the kelp L. nigrescens. When the kelp is absent, 2 other algal formations can be found at this intertidal level. In vegetational openings surrounded by individuals of L. nigrescens and in the absence of large grazers, large patches of Geldium chilense occur. In vegetational openings with abundance of grazers, patches of calcareous algae and bare rock are normally found. Through experimental manipulation the ecological changes of the understory algal assemblages following removal of the numerically dominant L. nigrescens were evaluated and with minor differences, the 3 functional groups of algae distinguished elsewhere (canopy forming, fugitive and obligated understory) also occur here. By experimental removal at different seasons and in presence or absence of sea urchins the occurrence of the 2 algal formations found in areas devoid of kelp is explained.