Invertebrate communities in holdfasts of the kelp Macrocystis pyrifera from southern Chile

Forty-two taxa of invertebrates and 1 species of fish were found in holdfasts of Macrocystis pyrifera in the giant kelp forest in Puerto Toro. Navarino Island, southern Chile. Maximum values of invertebrate density and biomass occur in late winter and spring, while higher values of species richness and diversity (H') are found in winter. Quantitative data indicate that 4 species (Pseudechinus magellanicus, Pagurus forceps, Halicarcinus planatus, Anasterias antarctica) are the determinant taxa in the overall changes of invertebrate biomass and density. Data on body size and average weight of these species indicate that neither growth nor juvenile recruitment are responsible for the overall pattern of change. Migration behavior of these species is a more likely explanation. The rate of accumulation of species of invertebrates to the holdfast is fast in small holdfasts, very slow in larger holdfasts, and the pioneer species are also found in larger and older holdfasts. Thus, the dynamic of species turn over does not follow a species replacement series typical of colonization processes described for non-growing habitats.