Priority effects in coral–macroalgae interactions can drive alternate community paths in the absence of top‐down control

Abstract

The outcomes of species interactions can vary greatly in time and space with the outcomes of some interactions determined by priority effects. On coral reefs, benthic algae rapidly colonize disturbed substrate. In the absence of top‐down control from herbivorous fishes, these algae can inhibit the recruitment of reef‐building corals, leading to a persistent phase shift to a macroalgae‐dominated state. Yet, corals may also inhibit colonization by macroalgae, and therefore the effects of herbivores on algal communities may be strongest following disturbances that reduce coral cover. Here, we report the results from experiments conducted on the fore reef of Moorea, French Polynesia, where we: (1) tested the ability of macroalgae to invade coral‐dominated and coral‐depauperate communities under different levels of herbivory, (2) explored the ability of juvenile corals ( Pocillopora spp.) to suppress macroalgae, and (3) quantified the direct and indirect effects of fish herbivores and corallivores on juvenile corals. We found that macroalgae proliferated when herbivory was low but only in recently disturbed communities where coral cover was also low. When coral cover was

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