The Great Barrier Reef Is Being Depleted by Pollution and Climate Change. Could ‘Coral IVF’ Save It?

The idea to restore coral reefs by intervening in the breeding process of coral came to Peter Harrison while he was drifting through trillions of coral eggs and sperm whirling in an underwater snowstorm during a mating ritual at Australia’s Great Barrier Reef that occurs each year in the romantic light of a full moon.

That moment, in the early 1980’s, kicked off a lifetime of research for Harrison, a professor at Australia’s Southern Cross University—and culminated in the development of a process that he describes as something akin to in vitro fertilization (IVF) for the reef.

In November, his research hit a remarkable milestone when coral babies born through the first coral IVF trial on the Great Barrier Reef in 2016 became mature coral and began to spawn—hopefully seeding a new generation of coral.
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Harrison says human intervention has become necessary to help repopulate the Great Barrier Reef because of a “perfect cocktail of destruction” that reefs are facing. This includes pollution, coastal development that damages ecosystems and warmer waters and intensifying storms—both of which can be at least partially attributed to climate change. “Reefs are losing corals, and more importantly, they’re losing breeding corals much faster than most of them are getting enough larvae now to replenish naturally,” he says.

Coral Spawning
Auscape/Universal Images Group/Getty ImagesHard coral (Acropora sp.), spawning in Lizard Island National Park, Great Barrier Reef, Queensland, Australia.

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The good news about his coral babies couldn’t have come at a more crucial time for the Great Barrier Reef, which is the world’s largest coral reef ecosystem, stretching some 1,420 miles along the northeast coast of Australia. The reef has suffered three major bleaching events in the past five years. These are changes in water conditions that cause corals to die. Many corals die as a result of the stress of mass bleaching events—further depleting the reef. According to the U.S. National Oceanic and Atmospheric Administration, temperatures could increase enough to trigger yet another mass bleaching event before January ends.

These bleaching events had profound effects on the reef. In 2020, a study by the ARC Centre of Excellence for Coral Reef Studies Queensland revealed that more than half of the corals in the Great Barrier Reef have been destroyed by warmer waters due to climate change.

Harrison, who has earned the title “coral IVF pioneer” from fellow researchers, may just know more than anyone about how corals get it on. He was part of the team that discovered that the Great Barrier Reef’s coral breed during a single yearly mass spawning event. That discovery transformed the world’s understanding of coral sexual reproduction.

Heron Island 2016 Coral IVF babies Acropora spathulata branching coral showing mature pink eggs and sperm packets CREDIT Christina Langley
Christina Langley Acropora. spathulata, Acropora branching coral is now five years of age with mature pink eggs ready for spawning and sperm packages.

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Harrison’s coral IVF process starts by capturing matter from multiple coral spawn slicks around the reef, which form in a pinkish film on the ocean’s surface during mass spawning events. He and his team use floating nets with booms similar to those used to contain oil spills—or a net that resembles a modified swimming pool skimmer.

In order to increase fertilization rates and genetic diversity, the eggs and the sperm of different colonies can be mixed. The larvae are left to grow in a floating pools anchored near the reef for about a week, where they’re safe from predators and they can be kept from drifting away.

Lapteres are usually settled on depleted reefs once the right time has come. The net can be opened to let the larvae flow over reef systems, or the larvae may be piped directly onto reefs. Scientists have also begun using AI-enabled robots called LarvalBots, which work like an “underwater crop duster,” to deliver larvae. You can place the larvae on small pieces of coral for transfer onto your reef.

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Professor Peter Harrison, pioneer of Coral IVF, measuring coral larvae concentrations at Heron Island
Southern Cross University Coral IVF pioneer, Professor Peter Harrison measures coral larvae concentrations in Heron Island, Australia.

Harrison’s work could be used to repopulate coral reefs around the world. The technique he has used to repopulate coral reefs in the Philippines is already working well. Half of the world’s coral reefs have died since the 1950s as the result of climate change, overfishing and pollution, according to a study published in September in the journal One Earth. It means the destruction of marine habitats and protection for coastal communities that are more vulnerable to extreme weather. By creating employment and attracting snorkel-toting tourist, reefs support local economies.

Lesley Hughes is a Macquarie University biology professor and member of the Climate Council, an Australian non-governmental organization. She believes coral IVF research can be used as part of an overall toolbox that will help the reef adapt to changing water and climate conditions. Other scientists are working on a host of creative solutions to save the reef—like a “sun shield” that can be sprayed onto the surface of the ocean.

But Hughes cautions that unless climate change is addressed, “any human intervention in reef communities, no matter how effective at a local scale, will be like trying to fix a broken leg with a bandaid.”

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Australia is a laggard on climate action among developed countries, and it’s one of the world’s biggest exporters of coal and liquefied gas. On June 21, UNESCO recommended that the Great Barrier Reef be placed on a list of World Heritage sites that are “in danger,” citing climate change as “the most serious threat” to the site. After a vigorous lobbying campaign by the Australian government, UNESCO decided to postpone a decision on the endangered status of the Great Barrier Reef until the next year.

Harrison agrees his solution isn’t a silver bullet, but he hopes it can play an important role in saving the world’s reefs. Says Harrison: “We’re hoping that this buys us enough decades so that we can continue to have functioning and breeding corals on enough reefs so that when we hopefully do manage climate change down to amore sensible level, we will still have corals and reef systems on our planet.”


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