Description
Predation can drive population and community structure and result in trophic cascades, increasing basal resource performance. There is increasing evidence that the non-consumptive effects of predators play an important role in these interactions. Through a series of laboratory and field experiments, I address gaps in knowledge on the prevalence of non-consumptive effects and trophic cascades in subtidal marine systems. First, I assessed the relative importance of consumptive and non-consumptive effects of an abundant microcarnivorous fish, the señorita (Oxyjulis californica) on the grazing behavior of its prey, the seaweed limpet (Lottia insessa), and in turn, its effects on habitat loss of the foundation species, the feather boa kelp (Egregia menziesi). Non-consumptive effects of predator presence drove these interactions, which caused limpets to decrease grazing activity, reducing frond breakage and habitat loss. These same interactions were observed in a natural field environment, with ambient levels of fish presence having similar effects on kelp strength as caged fish with and without access to limpets. Through both observational and manipulative studies, I monitored grazed and ungrazed fronds of E.menziesii through time and found that limpet grazing significantly increased frond loss. My study, provides convincing evidence of a trophic cascade driven by an apparent chemically mediated cue sensed by limpets that indirectly reduces kelp habitat loss. Such interactions may have large implications for assemblages of subtidal marine organisms.
