Collaborative Research: Shifting hotspots - How do consumer aggregations interact to influence resource heterogeneity and fluxes in streams?

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This project will determine where and when short-lived fish and long-lived mussel communities overlap (biological hotspot) and how this overlap affects the amount and spread of nutrients in two rivers. Nutrients feed aquatic plants that support riverine food webs, and it is hypothesized that animal aggregations can influence nutrient pollution. Understanding how these types of biological hotspots interact will further our knowledge of river function and provide targets for river restoration. To understand the ecology of fish and mussel hotspots in rivers, the investigators will use complementary approaches including field monitoring, experiments, and mathematical modeling. In addition, the PIs will train a post-doctoral researcher and undergraduate and graduate students as well as organize outreach workshops for K-12 teachers to develop programs associated with water quality and ecosystem services.The ecological processes that occur at animal aggregations (biogeochemical hotspots) are important for ecosystem health and can help mitigate nutrient pollution. Animal aggregations create patches where processes such as energy transfer and nutrient recycling are higher than outside of patches. Long-lived freshwater mussels live buried in the sediment in localized patches that serve as stable, long-term biogeochemical hotspots. In contrast, where shorter-lived, fish occur depends on flow conditions in rivers. Fish aggregations serve as mobile, widespread, short-term biogeochemical hotspots. This project quantifies the spatial and temporal overlap and interactions between mussel and fish aggregations in rivers. A field study will quantify fish and mussel abundance under different flow conditions in two rivers to determine patch size and location. A correlative field study will quantify ecological services performed by mussel and fish aggregations under low and higher flow conditions. Mesocosm experiments will use chemical techniques to track the movement of nutrients from fish and mussel aggregates through the rest of the food web. Lastly, computer models of ecosystem dynamics will be used to scale from fish and mussel distribution and flow data generated in the small-scale field study up to the whole river scale. A workshop will train teachers in water quality activities they can use in their classrooms.