Predicting spatial and temporal responses of herbivorous coral reef fishes to sediment runoff

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Tropical coral reefs are one of the world’s most biodiverse ecosystems but are rapidly degrading due to anthropogenic threats. Sediment runoff is associated with coral decline and algal dominance, yet we have a limited understanding of the impacts of sediment on reef organisms, including on herbivorous fishes that prevent uncontrolled algae growth. The investigators are examining the effects of sedimentation on several species of herbivorous reef fish, including whether they remain in or evacuate affected reefs. They are also characterizing the relationship between sedimentation, herbivory rates, and coral cover. Outcomes are informing reef management efforts by identifying critical sediment thresholds that may preserve herbivore biomass and algal removal rates. This project will provide research training for undergraduates, graduate students, and a postdoctoral scientist. The investigators are promoting coral reef education to local communities through a new partnership with the Hawai’i Science Inquiry Education Program (SIEP), an “early admit” college course that includes a culturally framed research experience for high school students. Finally, results of this project are being shared widely via a TV episode on Voice of the Sea, an established TV and online streaming series that connects research and culture.Sediment runoff is associated with coral degradation and shifts from coral- to algal-dominance. Herbivorous fishes are critical in preventing and/or reversing phase shifts, yet recent findings reveal extreme sensitivity of herbivorous reef fishes to sediment exposure, which in turn may lead to rapid decline in abundance and top-down algal control. The main goal of this project is to reveal how and to what extent sediment exposure erodes fish function in coral reef ecosystems. The investigators are combining field ecology, animal behavior, and mathematical modeling to address three main objectives: 1) Assessment of spatio-temporal functional responses of herbivorous fishes to sediment gradients in the wild; 2) Validation of behavioral responses of herbivorous fishes to sediment exposure in-vivo; and 3) Construction of a mechanistic framework for predicting consequences of sediment runoff for the delivery of herbivorous fish functions and coral-algal dynamics on vulnerable reefs. Overall, this study offers an integrated view of what characterizes sediment exposure limits and what goes wrong when limits are surpassed, while clarifying the mechanistic links between sedimentation, herbivory, and the risk of ecological phase shifts. Outcomes are establishing sublethal limits to sedimentation to inform conservation and management efforts and are being shared with stakeholders in Hawai’i. This project is jointly funded by the Biological Oceanography Program in NSF's Division of Ocean Sciences and the Established Program to Stimulate Competitive Research (EPSCoR).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.