Can Coral Reseeding Save the Great Barrier Reef?

Photo: ProDesign studio/Shutterstock

A group of scientists at the Great Barrier Reef can add another title to their resumes: coral reef matchmakers. They are "breeding" baby corals on the Great Barrier Reef, and the success of this spawning project could be used to save reefs around the world.

"This is the first project of its kind on the Great Barrier Reef to successfully re-establish a population of juvenile corals from larvae settling directly on the reef," Southern Cross University's Peter Harrison and lead researcher on the project said in a statement.

"The success of this new research not only applies to the Great Barrier Reef but has potential global significance — it shows we can start to restore and repair damaged coral populations where the natural supply of coral larvae has been compromised."

Coral growing across the sea

Fish swim through coral at the Great Barrier Reef
The coral of the Great Barrier Reef has struggled to survive assaults from climate change and coral bleaching. (Photo: William West/AFP/Getty Images)

Harrison and his team traveled to Australia's Heron Island in November 2016 during coral spawning season. During that time, the researchers collected coral eggs and sperm and used them to grow and cultivate more than a million coral larvae. These larvae were then planted on dead spots along the island's reef to see if they would settle into their new homes. Harrison and the other scientists also covered the larvae with underwater mesh tents to aid their growth.

The researchers returned this November to check on the status of their transplanted larvae, and they found that more than 100 of the larvae had established themselves on the reef and were thriving.

While that number may be small compared to the number the team reseeded onto the reef, Harrison is enthusiastic about the possibilities.

"The results are very promising, and our work shows that adding higher densities of coral larvae leads to higher numbers of successful coral recruits," Harrison said.

The project builds on previous work Harrison had done in the Philippines. Reefs there have suffered ill effects from blast fishing, the practice of using explosives to stun or kill fish for easier collecting. Harrison had conducted a similar restoration project there that resulted in the coral growing from larvae to "dinner plate-sized adult colonies within three years" that were also able to reproduce on their own.

The process also provides an alternative to coral gardening, a process by which pieces of healthy coral are broken off from their original locations and planted elsewhere or moving coral cultivated and grown in labs back to reefs. The process has had some success in the Caribbean, but Harrison believes the process "is expensive and often doesn't work very well."

A new hope for the Great Barrier Reef

Coral spawn
This is what the coral spawn looks like. Great Barrier Reef Foundation

Harrison conducted the Heron Island project with funds from the Great Barrier Reef Foundation, and based on its success, the Australian government is also stepping in to help Harrison expand the scope of the larval reseeding so that it can be reproduced on a much larger scale.

"With this new funding from the Australian government and continued support from the Great Barrier Reef Foundation and the Great Barrier Reef Marine Park Authority, our research team used the technique again this month at Heron Island to collect and 'match-make' coral spawn, producing mass quantities of coral larvae to deliver new coral 'babies' onto the reef," Harrison said.

Australia has struggled in recent years to protect the Great Barrier Reef. The reef suffered back-to-black years of bleaching in 2016 and 2017, with the reef described as being in a "terminal stage" of its life as a result of the bleaching. Efforts outlined by the country's Reef 2050 plan, including restricting port development and reducing agricultural runoff, haven't been able to counter warmer-than-usual temperatures.