EFFECTS OF EPIBIOSIS ON CONSUMER-PREY INTERACTIONS

In many benthic communities predators play a crucial role in the popul ation dynamics of their prey. Surface characteristics of the prey are important for recognition and handling by the predator. Because the es tablishment of an epibiotic assemblage on the surface of a basibiont s pecies creates a new interface between the epibiotized organism and it s environment, we hypothesised that epibiosis should have an impact on consumer-prey interactions. In separate investigations, we assessed h ow epibionts on macroalgae affected the susceptibility of the latter t o herbivory by the urchin Arbacia punctulata and how epibionts on the blue mussel Mytilus edulis affected its susceptibility to predation by the shore crab Carcinus maenas. Some epibionts strongly affected cons umer feeding behavior. When epibionts were more attractive than their host, consumer pressure increased. When epibionts were less attractive than their host or when they were repellent, consumer pressure decrea sed. In systems that are controlled from the top-down, epibiosis can s trongly influence community dynamics. For the Carcinus/Mytilus system that we studied, the insitu distribution of epibionts on mussels refle cted the epibiosis-determined preferences of the predator. Both direct and indirect effects are involved in determining these epibiont-prey- consumer interactions.