Habitat complexity impacts persistence and species interactions in an intertidal whelk

Although experiments have shown that habitat structure may influence the distribution of species and species interactions, these effects are still not commonly integrated into studies of community dynamics. Since habitat structure often varies within and among communities, this may limit our understanding of how various factors influence communities. Here, we examined how mussel bed complexity (the presence and thickness of mussel layers) influenced the persistence of whelks (Nucella emarginata) and interactions with a top predator (ochre sea stars, Pisaster ochraceus) and prey (mussels, Mytilus californianus). Results from a mark?Crecapture experiment indicate that whelk recapture rates are higher in more complex habitats, and laboratory experiments demonstrate that habitat complexity affects whelk feeding, growth, and nonconsumptive interactions with a keystone predator. Habitat complexity therefore has direct effects on species and also may lead to trade-offs among feeding, refuge, and other factors, potentially influencing the distribution of whelks and the effects of both whelks and sea stars on intertidal communities. These results demonstrate that habitat structure may play an important role in intertidal communities and other habitats and should be further considered in the experimental design of future studies of community dynamics.