THE ROLE OF HERBIVORY AND DESICCATION ON EARLY SUCCESSIONAL PATTERNS OF INTERTIDAL MACROALGAE IN SOUTHERN CHILE

The interactive effects of biological and physical factors on succession have received little attention. This study evaluates the importance of herbivory and desiccation on early successional patterns of macroalgae. A factorial experimental design was established, where grazers and seawater drainage were experimentally manipulated in the intertidal zone of Metri Bay in southern Chile. The percentage of macroalgal coverage was monitored monthly for 9 months. In quadrats without seawater drainage, the experimental plots were initially colonised by ulvoids which had no effect on species succession. The herbivores had an effect on abundances of ulvoids, but they did not affect algal successional sequences. In contrast, seawater drainage permitted the establishment of the crustose brown algae Ralfsia sp. and the herbivores facilitated the dominance of Ralfsia in drained quadrats because they preferentially consumed the ulvoids. This study demonstrates that the effect of desiccation and herbivory can create contrasting communities and that physical factors can modify the model that explains algal succession in southern Chile. © 1990.