A recently-awarded grant from Heising-Simons Foundation International, Ltd. (HSFI) will support a three-year study into the ability of corals to respond to thermal stress events, including prolonged periods of warmer-than-usual temperatures known as marine heat waves. By studying multiple reef-building corals in the Atlantic, Caribbean, and Pacific, the project aims to determine if there are potential benefits from thermal “stress conditioning” and, if so, to build cellular and molecular profiles of the more stress-tolerant corals.
This information can help scientists and managers to better predict the future of coral reefs under changing climate conditions, and fills a pressing knowledge gap in reef conservation efforts.
The project, which is set to begin in June 2022, brings together scientists from three institutions, including BIOS marine ecologists Samantha de Putron and Yvonne Sawall. Other members of the team include reef ecologist and BIOS adjunct faculty member Gretchen Goodbody-Gringley at the Central Caribbean Marine Institute and ecophysiologist Hollie Putnam at the University of Rhode Island.
This current project will build upon the results of a previous HSFI-funded investigation, which was completed in fall 2021 by co-principal investigators de Putron, Goodbody-Gringley, and Putnam. The team identified the importance of differing temperature regimes, or environmental history, among reef sites in Bermuda when studying coral physiology and the response to temperature stress. They also found that adult corals that survived high-intensity environmental stresses produce offspring that are “pre-conditioned” (or beneficially stress conditioned) to survive in new environments.
Additionally, their research uncovered that thermal stress events led to changes in the physiology of corals, which were both passed along to the next generation and did not involve alterations in the corals’ DNA structure. These are also known as epigenetic changes.
“Collectively, these results support that there is scope for Bermuda’s corals to gain resistance and resilience to marine heatwaves through stress conditioning,” de Putron said. “That conditioning could be through living in areas of higher thermal history or through manipulative stress events within the lab.”
The next step, which this new project will address, is to look at the thermal tolerances of corals across broad geographic regions to determine the similarities and differences in resilience and resistance. The team will study corals from Bermuda, the Caribbean, and Hawaii. In the lab, they will conduct stress tests on collected corals, with increasing water temperatures, based on performance ranges from the previous investigation. They will also study the corals in-situ, or in their natural environments, across the geographic locations.
“At the global scale, corals growing in areas with higher thermal variability tend to fare better than those in areas of lower thermal variability when they are faced with marine heatwaves,” Sawall said. “The Bermuda-based research will continue to provide a high-resolution test bed of coral resilience, and with this new grant we are excited to establish broader geographic applicability.”
The research at BIOS will take place at the Institute’s state-of-the-art mesocosm facility, which is in the process of being upgraded through a U.S. National Science Foundation grant for infrastructure improvements. The mesocosm facility is essentially a large outdoor aquarium with a series of individual tanks, each with fresh seawater and the ability to manipulate variables for different experimental designs, such as temperature, pH, or light. The performance of the corals will also be followed on the reef using novel, high-tech in-situ measurement chambers.
With the ability to control the environment and closely monitor the corals in the mesocosm, as well as collect the same performance data from the corals using the in-situ chambers, the team will look at the magnitude and duration of thermal exposure that is needed to provide a beneficial stress conditioning response in corals. They will also be able to identify key molecular and cellular mechanisms that enable optimal function.