Helping Corals Survive the Climate Crisis

Jun 01 2021
Photo courtesy Brook Peterson / Ocean Image Bank

Coral reefs are among the most diverse and valuable ecosystems on the planet. 

They make up a small fraction of our ocean floor, yet the list of reasons why they are important is long. Coral reefs underpin the safety, culture, food, and economic security of almost one billion people. Not to mention, they support more than a quarter of all marine life and play a key role in maintaining a healthy ocean. But in the last 50 years, half of the world’s coral reefs have died in the face of unprecedented climate changes and growing local pressures. Without drastic intervention, experts suggest warming ocean temperatures could bleach these incredible species to death by the end of century. 

To slow the decline of our ocean’s coral reefs, the Paul G. Allen Family Foundation is committing more than $7 million toward research to revolutionize what’s possible in the fight to help corals survive the climate crisis.  

“These grants build on the Foundation’s longstanding commitment to coral reefs,” said Jody Allen, co-founder and chair of the Paul G. Allen Family Foundation. “We are at a critical juncture with coral reefs facing extinction and the world must continue to invest in actionable research that ensures their preservation and long-term survival.” 

Using the latest advances in biomedical science, technology, and coral reef ecology, the foundation is supporting four teams of researchers across the globe answer the essential question – can we find a way for corals to survive long enough for us to act on climate change? 

Finding Nature's 'Super Corals'

Global Search project lead Prof. Christian Voolstra collecting samples underwater at Ducie Island, one of the world's most remote reefs in the world. Photo courtesy Pete West

A global team of scientists across the globe are on the lookout. They are searching our ocean far and wide for naturally resilient coral reefs. These “super corals” have two critical characteristics separating them from other corals: they can handle rising ocean temperatures and they can bounce back from the impacts of ocean warming.   

To find these heat-tolerant corals, the team is using an experimental system called the Coral Bleaching Automated Stress System, or CBASS for short. Think of CBASS as an ultra-portable box with similar principles as a cardiac stress test. Researchers graft fragments of coral in the field and simultaneously expose them to varying temperatures to test their bleaching response. At the end of the 18-hour process, the scientists can see which coral colonies are resilient to higher ocean temperatures and which ones aren’t.  

“We’re basically putting corals on a racetrack and watching how they perform,” said Christian Voolstra, a professor at Konstanz University of Germany. “The good sprinters will also be good runners and, as such, will perform better during episodes of long-term heat stress on coral reefs.”

The team believes nature’s own “super corals” hold the solutions the world needs to help protect and restore coral reefs. By learning where to find them, researchers say we can better understand the environmental conditions that shape these corals, and uncover the molecular and genetic underpinnings that makes them heat-tolerant. Or in the larger scheme of things, a “climate change survivor.” Identifying them also helps governments, organizations as well as scientists prioritize their colonies for conservation and restoration. But maybe the most important role these corals play is the one that will help their species survive the long-term effects of climate change. As a superior source material for coral restoration, they could potentially improve the resiliency and survival of the next generation. 

“This is a ‘nature does it best’ approach,” said Voolstra. “These ‘super corals’ are solutions nature has evolved, which means they evolved to exist in harmony with the rest of the reef. There’s no unforeseen side effects here.” 

Giving Coral a Helping Hand

Divers secure coral nubbins to experimental racks for a Reciprocal Transplant Experiment in Kaneohe Bay. Nubbins of the rice coral, Montipora capitata, are in the foreground, and the rack to the right holds finger coral, Porites compressa. Photo courtesy Shayle Matsuda

To give corals a fighting chance against climate change, we need to accelerate the natural evolution of heat resilient corals so they can help save themselves.  

By manipulating the epigenetics of coral, scientists have shown that they can help coral reefs cope with the impacts of climate change, particularly ocean warming and acidification. Coined human assisted evolution of corals and pioneered by Dr. Madeleine van Oppen from the Australian Institute of Marine Sciences (AIMS) and the late Dr. Ruth Gates at the Hawai’i Institute of Marine Biology (HIMB), this research uses a collection of interventions. From selective breeding to environmental conditioning and the manipulation of algal symbionts, this range of techniques all speed up the naturally occurring evolutionary processes in coral. Considered radical at the time the foundation first invested in this research in 2013, van Oppen and Gates have since revolutionized coral research.

“The world received it as two women with crazy ideas that had too many risks that were never going to work,” said van Oppen. “[The research] has spawned a movement across the world, with now many scientists conducting active research on assisted evolution of corals.” 

The foundation’s previous five years of support helped teams in Australia and Hawai’i develop the infrastructure of this research. In the next phase of investment, both teams will continue to collaborate, but will be focused on two promising approaches.

We are at a critical juncture with coral reefs facing extinction and the world must continue to invest in actionable research that ensures their preservation and long-term survival.”

— Jody Allen

In Australia, van Oppen’s lab says the key to coral survival might just be in the hands of the single cell algae that live within them. Called algal symbionts, researchers are conditioning them to withstand greater temperatures. After reintroducing these symbionts to corals, van Oppen says early results show this technique is increasing a coral’s heat tolerance. In the new phase of research, van Oppen plans on transplanting these corals in the field for the first time. And since corals naturally expel some of the symbionts, her hope is that these conditioned algae will end up in wild corals creating new breeds of coral that can survive heat and hopefully climate change for years to come. 

Meanwhile, in Hawai’i, Dr. Crawford Drury and the HIMB team are continuing Dr. Gates’ legacy. They are identifying heat resilient corals in the field, breeding them in the lab, and exposing them to anticipated future climate conditions to see how they fare. The most resilient of these juvenile corals will then be transplanted. This is significant because it marks the first time these researchers will be able to monitor the results of selective breeding in the field providing data-driven recommendations for other breeding and restoration programs worldwide. 

“It is imperative that we determine how to support self-recovery and the long-term persistence of reefs,” said Dr. Drury. “Selective breeding is an important step toward achieving this goal.” 

Helping Baby Coral Survive

To help restore our ocean’s badly degraded reef systems, Professor Peter Harrison with Southern Cross University in Australia is focused on increasing the survival rate of juvenile corals.  

Most baby coral polyps die just weeks or months after mass spawning events. Some succumb to disease or stress and others are eaten by predators. Another reason is that many reefs around the world have been overtaken by seaweed, limiting the surfaces where baby coral can grow. This study will help understand if ”weeding” reefs could help survival rates for baby coral. 

Harrison says his pilot studies show promising early results. Baby coral that settled on areas physically cleared of excess seaweed fared much better than their counterparts on seaweed-dominated systems. Through the foundation’s support, Harrison and team plan on doing this on a larger scale and incorporate new elements to improve the survival rates for newly settled baby corals. 

“Through clearing larger areas of algae, feeding new larvae in culture, producing many millions of larvae, and settling them in new designs like 3D tiles, we should see an increase in the rate of survival of juvenile corals in this critical early life stage,” said Harrison. “This is the stage when most baby polyps die, and we need to overcome that bottleneck to successfully restore degraded reefs.” 

This is the stage when most baby polyps die, and we need to overcome that bottleneck to successfully restore degraded reefs.

— Professor Peter Harrison

Developing coral embryos as seen under the microscope. Photo courtesy Peter Harrison
Larval culture pool for rearing millions of larvae directly on the reef. Photo courtesy Peter Harrison

Surviving Us

The plight of coral reefs is caused by the ongoing climate crisis, and while this groundbreaking research helps buy time and works to improve coral resiliency, in the long-term, coral survival is dependent upon human action. For the future of corals, it’s a matter of whether we can act in time.  

The Value of Coral Reefs


marine life supported

$2.7 trillion

value per year

1 billion

people rely on coral reefs for food, income, and protection