Collaborative research: Exploring the generality of light, nutrient and predator constraints on food chain efficiency

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This research will examine how the efficiency of energy flow through food webs is affected by sunlight, nutrients, and predators. Sunlight and nutrients affect the chemical composition of algae, including the amounts and ratios of carbon, nitrogen and phosphorus as well as essential fatty acids (EFAs). In addition, light and nutrients can determine which algal species are present, and their digestibility for herbivores. Variation in carbon:nutrient ratios, EFAs, and digestion resistance of algae can determine the production of herbivores, but little is known about how these effects propagate to animals at the top of the food chain, e.g., fish and other carnivores. The investigators will conduct three large-scale experiments to investigate effects of light, nutrients, carnivore species, food web structure, and nutrient ratios on food chain efficiency. They will also develop next-generation, stoichiometrically-explicit computer models which will provide mechanistic understanding of the experimental results, and expand the scope of the research.This project will provide critical information for decision-makers involved in water quality protection and fisheries management. For example, fisheries yields depend on food chain efficiency, specifically the proportion of algae production that is converted into fish or shellfish species harvested by humans; eutrophication results from the inefficient use of plant production by herbivores after excessive nutrient enrichment; carbon storage in deep waters and sediments (which reduces greenhouse gases in the atmosphere) is related to energy that is not consumed in pelagic food chains; and the concentrations of contaminants at each trophic level is affected by energy flow through food chains. In addition, many global-scale environmental problems, such as eutrophication and climate change, alter the supplies of light and nutrients, and can mediate food chain efficiency. In addition the project will provide numerous opportunities for undergraduate and graduate students, who will be actively engaged in all aspects of the research.