Dissertation Research: How does biodiversity influence resource subsidy flux? A test with freshwater mussels and aquatic-terrestrial linkages

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Species loss, habitat alteration, and climate change are causing dramatic changes in the diversity and function of ecosystems. This project asks how the number of species present influences the transfer of nutrients and energy among organisms. Previous experiments suggest that mussels provide nitrogen to streams during summer low-flow seasons. Increased nitrogen availability can trigger increases in the abundance of algae and, subsequently, of grazing aquatic insects. Importantly, when more species of mussels are present this transfer of nitrogen is enhanced, suggesting that the diversity of mussel assemblages increases the quantity of nutrient subsidies. Effects of nitrogen subsidies may extend beyond the stream itself, as adult aquatic insects are an important food source for terrestrial predators in riparian forests. Experiments will be conducted using freshwater mussels to investigate how the diversity of freshwater mussel assemblages influences the rate at which the mussel community makes nutrients available to the stream ecosystem and to terrestrial predators. Field and laboratory experiments will be used to see if the emergence rates of adult aquatic insects and the abundance of riparian spiders increase when more mussel species are present. Stable nitrogen isotopes will be used to quantify nutrient subsidies and determine how mussel-derived nutrient subsidies move through stream and riparian food webs. This research will contribute to our understanding of the relationship between biodiversity and ecosystem function, which will ultimately help scientists predict the consequences of extinctions and climate change on ecosystem processes. It also will enhance our understanding of the ecological importance of freshwater mussels, a globally threatened fauna.