The applicant will use this Polar Postdoctoral Fellowship to study top-down effects on community structure (habitat choice and behavior of amphipods, the dominant mesograzers) in macroalgal communities in the vicinity of Palmer Station, Antarctica, where amphipods are not only extremely abundant, but their distributions are very different on palatable vs. unpalatable macroalgae. Pilot studies have suggested that these differences in community structure may be driven by algal chemistry and predation. The effects of algal chemistry on amphipod habitat choice, both in the presence and absence of predators will be tested experimentally, as will the question of whether amphipod host-alga choice results in any reduction of predation risk. Mesograzers in general, and amphipods in particular, are an essential trophic link in marine systems worldwide, and in particular, are a critical component of antarctic near-shore ecosystems. However despite their high abundance and species richness, little is known of their functional ecology or trophodynamics, and little research has investigated the trophic dynamics, behavior, or ecology of these organisms. This project will work out the basic biology of the system, by examining amphipod distributions on Himantothallus (a brown macroalga) and in the stomach contents of Notothenia coriiceps (a small cod-like antarctic fish) and determining whether prey selectivity of amphipod species is occurring. A series of laboratory experiments will investigate the influence(s) of predators, algal chemistry, and thallus structure on amphipod behavior and habitat choice, and test the predation risk associated with amphipod host-alga choice.
