New groundbreaking research from Southern Cross University has uncovered remarkable variation in coral heat tolerance on the iconic Great Barrier Reef. This discovery offers a glimmer of hope, suggesting that the key to the reef’s recovery and adaptation may lie within the genetic diversity of its corals.
In a pioneering study, researchers utilized a cutting-edge portable experimental system to measure the bleaching thresholds of over 500 colonies of the table coral Acropora hyacinthus.
Conducted at sea across 17 reefs spanning the Great Barrier Reef, this research was spearheaded by Southern Cross University PhD candidate Melissa Naugle in collaboration with a team from Southern Cross University, the Australian Institute of Marine Science (AIMS), the University of Queensland, and the Research Institute for Development in New Caledonia as part of the Reef Restoration and Adaptation Program (RRAP).
“We found heat-tolerant corals at almost all the reefs that we studied, highlighting how corals across the entire Great Barrier Reef may hold genetic resources that are important for protection and restoration,” said Melissa.
“This is important news for corals, which are experiencing the 4th global mass bleaching event and unprecedented summer sea temperatures on the Great Barrier Reef. Naturally occurring heat tolerance variation is crucial for corals to adapt to climate warming and for the success of restoration initiatives.”
In another recent study, co-author and fellow Southern Cross University PhD candidate Hugo Denis substantiated these findings by uncovering widespread variation in heat tolerance within a different coral species. These groundbreaking results carry significant implications for the future of coral reefs.
“Differences between individual corals are the fuel for natural selection to produce future generations of more tolerant corals,” said Dr Line Bay, co-author and Senior Principal Research Scientist and Research Program Director at AIMS.
“Developing a solid understanding of this variation is crucial to understanding how corals will adapt to climate warming.”
Dr. Cedric Robillot, Executive Director of the Reef Restoration and Adaptation Program, said: “This work highlights the availability of naturally heat-tolerant corals that can be targeted by RRAP as a large-scale reef restoration and conservation effort to protect this critical ecosystem from warming ocean temperatures that are already locked in from climate change.”
Dr. Emily Howells, co-author and Senior Research Fellow at Southern Cross University and Project Lead in the Reef Restoration and Adaptation Program, said: “Heat tolerance variation can be useful for restoration programs such as selective breeding, which may accelerate adaptation to produce offspring better suited to warmer waters. However, this outcome depends on how much of the heat tolerance variation we observe is tied to heritable gene variants.”
The corals identified as the most heat-tolerant in this study are currently the focus of a selective breeding trial under the Reef Restoration and Adaptation Program.
The study not only revealed the wide variation in coral heat tolerance but also delved into the factors contributing to this diversity.
“In this paper, we explored many of the environmental influences that shape heat tolerance, like thermal history, nutrient concentrations, and the symbiotic algae that live inside coral tissue,” said Melissa.
While the study emphasizes the significance of environmental factors like sea temperatures in influencing heat tolerance, it also uncovered substantial variation that cannot be solely attributed to the environment, pointing to genetic disparities among individual corals as a likely factor.
“Next, we’ll analyze DNA-sequencing data from these individuals to identify gene variants associated with heat tolerance. This can help us understand the adaptation potential of natural coral populations and inform selective breeding work,” Melissa said.
“While restoration initiatives like selective breeding may strengthen coral populations, reducing greenhouse gas emissions is most crucial to give coral reefs the best future possible.”
Journal reference:
- Melissa S. Naugle, Hugo Denis, Véronique J. L. Mocellin, Patrick W. Laffy, Iva Popovic, Line K. Bay & Emily J. Howells. Heat tolerance varies considerably within a reef-building coral species on the Great Barrier Reef. Communications Earth & Environment, 2024; DOI: 10.1038/s43247-024-01649-4
