Refuge availability increases kelp consumption by purple sea urchins exposed to predation risk cue

Abstract

Predatorprey interactions in kelp forests have been a topic of research for many decades. Prey anti-predator behaviors (e.g. reducing foraging) are an important component of predatorprey interactions and can cause impacts on primary producers (trait-mediated indirect interactions, TMIIs). In kelp forests, the interactions between spiny lobsters and their sea urchin prey can have significant impacts on kelp biomass. In a laboratory mesocosm experiment, I found that both spiny lobster Panulirus interruptus waterborne risk cue and urchin refuge availability significantly affected kelp Macrocystis pyrifera consumption by urchins Strongylocentrotus pur- puratus. However, the effect of predator risk cue on kelp consumption was magnified in the absence of an urchin refuge. This study provides further evidence that TMIIs are important in lobsterurchin interactions, and suggests that refuge availability, by influencing foraging behav- ior, may also shape the important role of urchins in kelp forests.