Cascading effects of predator diversity in a marine food web

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Intellectual merit: The general significance of marine biodiversity is widely accepted. For example, there are several compelling examples of the importance of genetic, species, and functional group diversity in regulating community productivity, invasibility, and stability in benthic marine habitats. Such empirical research and basic ecological theory support the assertion that preserving biodiversity should be a top conservation priority. Yet because there have been few experimental investigations of the effects of predator diversity, we cannot predict and may not even recognize the cascading effects of predator extinctions. The diversity of vertebrate predators has declined, sometimes precipitously, in nearly all aquatic and terrestrial communities as a result of over harvesting and habitat loss. This phenomenon is especially well documented in some marine ecosystems where over fishing has reduced top predator biomass by 85% and species richness by 10-50%. To understand the consequences of these changes in marine predator composition and diversity we clearly need to begin to perform relevant experiments in marine ecosystems. This study will determine the cascading effects of predator composition and diversity on lower trophic levels by manipulating the structure of a benthic estuarine food web in North Carolina. Using a diverse and well-studied community of macroalgae, macroinvertebrate herbivores, and crustacean and vertebrate predators, the investigators will perform experiments in the field and in outdoor mesocosms to answer three basic questions: Question 1: How does predator identity and richness directly affect herbivore communities? Question 2: How does predator identity and richness indirectly affect plant communities and primary production? Question 3: Does prey immigration mediate predator diversity effects? Broader impacts: This project will expand ongoing collaboration between researchers at the Virginia Institute of Marine Science (VIMS) and the UNC's Institute of Marine Science (IMS) on the relationships between marine plant and herbivore biodiversity and ecosystem functioning. This research will be the first of its kind in any ecosystem and fits within the Biological Diversity in Marine Systems special theme of emphasis of the NSF Biological Oceanography Program. The results will help scientists and policy makers understand the consequences of declining predator diversity, potentially benefiting society by helping to conserve similar systems. Additional broader impacts will result from several outreach activities including: the mentoring of middle and high school students, summertime marine ecology children's camps organized with the Morehead Planetarium and Science Center, and a close collaboration with state fisheries managers and local fishers.