BARNACLE WALLS AS MEDIATORS OF INTERTIDAL MUSSEL RECRUITMENT - EFFECTS OF PATCH SIZE ON THE UTILIZATION OF SPACE

Recruitment of the competitively dominant Perumytilus purpuratus to the mid rocky intertidal zone in C Chile depends upon the presence of recruitment-mediators such as mussel clumps, filamentous algae or barnacle shells. At Las Cruces, changes in number of individuals and percent cover of sessile species were recorded in different sized patches of bare rock. All patches were surrounded by barnacle beds. Throughout the study, P. purpuratus recruited only on the walls of adult barnacles that formed the patch borders, and never on bare rock; barnacles recruited directly on the bare surface of cleared patches. Mussel recruits outnumbered those of barnacles in patches smaller than 35.5 cm2. Above this critical patch area, the number of barnacle recruits was progressively larger than that of mussels. A barnacle-dominated substratum may change to a mussel-dominated one depending upon the relative abundances of small and large patches. A barnacle bed disrupted in several small patches will provide more substratum for mussel recruitment than if only few large patches are produced. -from Authors