CAREER: Quantifying the contribution of chemosynthesis to stream productivity

Life in streams, and other habitats, is predominantly supported by biomass that is made from the sun’s energy via photosynthesis at the base of the food web. According to the current paradigm, fish and other aquatic organisms consume biomass produced by photosynthesis locally in the water and supplemented by photosynthesis on land, which washes into waterways as dead and decaying organic matter. Emerging evidence suggests that photosynthesis is not, however, the only pathway which supports stream life. Alternative chemosynthetic pathways for generating biomass may also provide food sources for insects and fish, especially where light and oxygen are limited. Preliminary results show chemosynthetic biomass is produced from methane, sulfur, and ammonia oxidation, even where the key substrates were not present above detection limits in the water. Chemosynthetic biomass likely develops in dark, slow-moving waters, such as those between gravels and leaves, in backwater habitats, or in the subsurface waters. The importance of these alternative biomass pathways as food resources for stream animals is poorly understood, limiting stream science, models, and management to assumptions that food source production occurs only via light-dependent photosynthesis. This project will investigate how differences across stream landscapes support varying biomass production pathways. Then estimates of how these pathways contribute to the growth of insect consumers that are the base of food webs supporting fish will be made. Media, educational materials, and training programs which explain project results in the context of interconnected hydrology, biogeochemistry, and ecology will be developed and disseminated. This novel CAREER project will quantify chemosynthetic primary productivity and contributions to stream animal biomass across a range of gravel-bed stream and floodplain habitat types. By measuring rates of chemoautotrophy, methanotrophy, and photosynthetic primary production across varying biogeochemical conditions and hydrologic gradients, it will be possible to assess the relative contribution of chemosynthesis to biomass fixation. Stable isotope mixing models will be used to estimate contributions of each fixation pathway to invertebrate animal biomass. The results will be synthesized to compare variation in food resource usage across habitats in floodplain environments to assess the role of landscape heterogeneity. Classes will be developed for in-classroom and field teaching at UNC Chapel Hill and Flathead Lake Biological Station, in conjunction with mentorship of a graduate student and undergraduates. Two short public-access documentaries will explain how landscape structure can contribute to ecosystem services in rivers and correspond to in-person exhibits. The combined research and teaching objectives will enhance communication between research communities and local stakeholders. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2543702 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT,01003031DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Amanda DelVecchia | Institution: University of North Carolina at Chapel Hill, CHAPEL HILL, NC | Award Amount: $665,539 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2543702 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2543702.html