This project studied the dynamic nature of the partnership between reef-building corals and their symbiotic algae (Family Symbiodiniaceae). This partnership is critical to understanding how coral reefs evolved to become one of the dominant ecosystems of shallow tropical seas, but also why corals are disappearing at unprecedented rates due to episodes of heat-induced coral “bleaching” (the expulsion of algal symbionts, which causes the coral to turn pale or white) which has led to mass mortalities of corals around the world. 

This project focused on the ability of many coral species to shuffle different algal symbionts in favor of more thermally tolerant types (in particular Durusdinium trenchii) as oceans continue to warm. It used controlled bleaching and recovery experiments to quantify and rank (for the first time) the ability of different Caribbean coral species to shuffle symbionts in favor of D. trenchii, and showed how coral-algal symbioses are even more dynamic than previously thought, including understudied species. 

In another first, it formally quantified and compared the increase in the coral bleaching threshold (in °C) caused by changes in symbiont communities in favor of D. trenchii across different Caribbean coral species. This is particularly important given the recent marine heatwave of 2023, which devastated coral reefs in Florida and around the Caribbean region. This project also monitored changes in algal symbiont communities following the heatwave event in Florida and also assessed longer-term changes (up to 20+ years) on western Atlantic reefs to quantify the magnitude of symbiont shifts taking place naturally. 

In terms of applied science, this project tested novel methods for manipulating coral algal symbioses, such as using tissue grafts, and also developed ways to provision new generations of corals with heat-tolerant symbionts early in their development. These methods are important because they can help improve coral restoration pipelines designed to produce and outplant corals on reefs that are better able to deal with warming temperatures. Restoring corals using interventions such as these is important not just for saving these critical marine ecosystems, but because coral reefs also protect coastlines from the damaging effects of flooding during tropical cyclones, typhoons, and hurricanes, and have great economic value for communities along tropical and subtropical coastlines around the world. Indeed, we were able to leverage this research into new projects funded by DARPA (2022-24, to develop resilient corals for hybrid reef deployments), and by NOAA (2024-2028, to integrate interventions into the restoration of resilient corals on wild reefs across a network of restoration practitioners).  

This project also helped educate the next generation of scientists, directly helping train one postdoc, three Ph.D. students, two master’s students, and numerous undergraduates at the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Science. Content from the grant was also incorporated into graduate (MBE 618 Biology, Ecology, and Conservation of Reef Corals) and undergraduate (MBE 407  Molecular Ecology and Physiology of Reef Coral Symbioses) classes at the University of Miami. It also provided opportunities for 40 individuals to participate in field research on coral reefs in Florida, Bermuda, and The Bahamas, and also led to training opportunities for five interns, research technicians, and postdocs at the John G. Shedd Aquarium in Chicago.  

Finally, this project helped disseminate messages about disappearing coral reefs, the need to develop more heat-tolerant corals, and the value of coral reefs in coastal protection, to a number of mass media audiences. Highlights include appearances on CBS 60 Minutes with Anderson Cooper (Mr. Cooper participated in a cruise with our teams in the Florida Keys) and Project Paradise, a documentary feature currently on the film festival circuit. We also developed content and messaging on permanent display in Shedd Aquarium’s Wild Reef exhibit (2 million visitors per year), and ran public-facing experiments on coral thermotolerance at the Phillip & Patricia Frost Museum of Science in Miami (~900k visitors per year, 2019-2024). Finally, our work was highlighted by numerous local print and radio media outlets in South Florida, Chicago, and The Bahamas, and through our active social media platforms to reach broad and diverse audiences.

Last Modified: 04/18/2025
Modified by: Ross Cunning