Consumer mobility predicts impacts of herbivory across a wave stress gradient

Environmental stress impedes predation and herbivory by limiting the ability of animals to search for and consume prey. We tested the contingency of this relationship on consumer traits, and specifically hypothesized that herbivore mobility relative to the return time of limiting environmental stress would predict consumer effects. We examined how wave-induced water motion affects marine communities via herbivory by highly mobile (fish) versus slow moving (pencil urchin) consumers at two wave-sheltered and two wave-exposed rocky subtidal locations in the Galapagos Islands. The exposed locations experienced 99th percentile flow speeds that were 2-5 times greater than sheltered locations, with mean flow speeds >33 cm/s vs <16 cm/s, 2-7 times higher standing macroalgal cover and 2-3 times lower cover of crustose coralline algae than the sheltered locations. As predicted by the Environmental Stress Hypothesis (ESH), there was a negative relationship between mean flow speed and urchin ...