Award: OCE-1329408

Intellectual Merit Since 1997, the Shark Bay Ecosystem Research Project of Florida International University has investigated the ecological importance of marine top predators. Our long-term datasets allowed us to take advantage of an extreme climatic disturbance (a marine heatwave) to experimentally investigate the importance of large marine predators in protecting ecosystems from long-term changes as a result of such events. Specifically, we tested whether the loss of tiger sharks from this previously pristine seagrass ecosystem would result in a shift from a system dominated by lush and complex seagrass pastures to one dominated by fast-growing but sparse seagrasses that provide less habitat for fish and invertebrates and less ecosystem services in the form of carbon sequestration. In addition, we documented the responses of seagrass to the heatwave over a large spatial extent and its impacts on large animals, like sea turtles. The æmarine heatwaveÆ resulted in a massive (>80%) decline in the foundational seagrass species that persisted throughout our study. This had a profound impact on the health of sea turtles. Before the heatwave, most turtles were in good body condition but afterwards virtually none were. Cameras deployed on sea turtles showed that they were not able to find healthy seagrass beds to feed on. Our experiments provide strong evidence that without intact populations of large tiger sharks – a predator of herbivorous turtles and sea cows - the marine heatwave would have resulted in a shift from a high-value habitat (in the form of structure for fish and invertebrates and high carbon sequestration) to a low-value one due to expanded grazing by tiger shark prey. The presence of tiger sharks should facilitate the recovery of the ecosystem. This shows that maintaining intact predator populations is likely especially important for maintaining healthy ecosystems in the face of extreme events that are likely to increase due to climate change. Broader Impacts During this project we conducted dozens of public lectures in Shark Bay, which is a destination for almost 100,000 tourists annually. We maintained and updated our project website (sberp.org) that provides details on our research methods, projects, and results, species fact sheets, image and video galleries, and teacher resources. An eBook is currently being developed that will feature information collected during this grant. Video vignettes and clips have been disseminated through the website, a YouTube Channel, and Heithaus lab blog (heithauslab.blogspot.com). We conducted professional development sessions for teachers that trained them to use the Shark Bay "Exploration of a Seagrass Ecosystem" project based video and accessory materials, which are available online (sberp.org) and have been distributed at science teacher meetings. In the field, we provided research experiences for 11 undergraduate students, three recent graduates, two graduate students and a postdoctoral scientist Data have been and are being archived in searchable databases with the Florida Coastal Everglades Long Term Ecological Research Program. Last Modified: 06/19/2015 Submitted by: Michael Heithaus