on 28 Aug 2020
Can the world’s coral reefs, vital to the health of our oceans, be artificially engineered to survive the climate crisis?
Coral reefs are alive in every sense. They are huge structures created by the long-term work of tiny coral animals. You can think of coral reefs as underwater cities that provide refuge for abundant and diverse marine creatures. The question now is: can these delicate systems survive climate change?
Coral reefs thrive in warm, clear ocean waters, protecting our coastlines and providing habitat for fish and other animals while driving tourism and local economies. Reefs are particularly important in Southeast Asia and the Indo-Pacific.
These ecosystems are beautiful, complex and full of activity, but they are seriously threatened. Because of their sensitivity, coral reefs serve as a canary in the coal mine for ecosystems around the world; they are among the first to be seriously impacted by climate change and pollution. A mass die-off of corals would have far-reaching effects on interconnected coastal and ocean ecosystems and the animals that rely on them – humans included.
Coral reef ecosystems are beautiful, complex and full of activity, but they are seriously threatened
With climate change, the corals that build reefs face increasingly stressful temperatures, which leads to a breakdown of their beneficial relationship (symbiosis) with the tiny, single-celled algae that live inside their tissues. This breakdown is called ‘bleaching’, for the characteristic bone-white appearance of stressed corals. When bleaching occurs, many corals will die, eroding the structure and function of reefs.
These bleaching events are becoming more frequent and severe as global temperatures increase over time, threatening the long-term survival of coral reefs.
Our work at the Hawaiʻi Institute of Marine Biology addresses this challenge with an active approach we call Assisted Evolution, funded by the philanthropy of the late Paul G. Allen. Our research aims to harness the power of diverse, natural processes that corals and other animal populations use to deal with changing conditions.
Bleaching events are becoming more frequent and severe as global temperatures increase
“Like ancient agricultural practices, we use natural coral reproduction events to select for traits we care about—in this case, high temperature tolerance”
Among the most promising of these techniques is selective breeding. Like ancient agricultural practices, we use natural coral reproduction events to select for traits we care about—in this case, high temperature tolerance identified in experiments or bleaching surveys. Our study corals spawn late at night due to cues from summer new moons, releasing eggs and sperm simultaneously. We collect and cross these eggs and sperm to produce the next generation of young corals with improved temperature tolerance.
A recent experiment showed that at two months old, these corals could cope with 3°C (or 5°F) warmer temperatures than corals whose parents we had not selected. To understand their resilience, we study the DNA of each coral, identifying genes that might impact temperature tolerance and spread through coral populations in the future. We have found that we can manipulate the specific genes coded by these DNA targets and change the rate of bleaching in experimental corals. While this technique is not yet suitable for application on a wild reef, it is an important step towards our goal of more resilient reef ecosystems.
By manipulating their DNA, corals can be made more resilient
These tools will be truly useful when we can apply them on a wide scale, so we have been moving our research from the laboratory into the field. Recently, we began restoration efforts at three sites on Oʻahu, attempting to harness particularly hardy corals to achieve climate-wise coastline protection. To do this, we attach temperature tolerant coral ʻoutplantsʻ to the bottom, much like planting trees to restore a forest. These outplants help create a wave-resistant natural infrastructure that protects our coastlines from storms and flooding and provides a model to help us understand how our efforts today can still be viable in a century, accepting that conditions in the future will be quite different from the present day.
While Assisted Evolution does provide a glimpse of hope for the future of coral reefs, we are still developing our understanding of its possibilities and consequences.
This complex task is made more difficult by the urgency of the problem. Research suggests that natural processes can keep up with some amount of increased oceanic temperatures, but this ability is limited and unclear for all coral species. Our dedicated team of specialists is actively pushing the frontiers of coral biology in search of productive strategies to ensure coral reefs remain viable for future generations.
About the Author
Dr Crawford Drury is interested in coral reef resilience from the perspective of genetics, spatial patterns and ecological flexibility. His research at the Gates Lab concerns the detection and prediction of resilient corals, understanding reproductive outcomes in corals, and the impacts of genetic diversity, all to address responses to challenges faced by reefs worldwide. He holds a doctorate from the University of Miami, Rosenstiel School of Marine and Atmospheric Science.