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‘Coral gardening’ aims to help the Great Barrier Reef fight climate change

Underwater gardens, where coral fragments grow, are part of efforts to protect reefs from climate change

A shoal of fish swims through a rift in the coral along Australia's Great Barrier Reef. Bleaching events caused by warming seas have caused significant damage to the reef. (Photo by Michael Robinson Chavez/The Washington Post)
A shoal of fish swims through a rift in the coral along Australia’s Great Barrier Reef. Bleaching events caused by warming seas have caused significant damage to the reef. (Michael Robinson Chavez/The Washington Post)


The world off the northeast coast of Australia is magical but beleaguered, a place of stunning colors in the good times but ghostly white in the bad. Evil has happened repeatedly in recent years, as warming seas linked to climate change have bleached the vast coral ecosystem below.

But thanks to a symbiotic collaboration between five tourism companies and marine scientists from the University of Technology Sydney, “coral gardening” at underwater nurseries is trying to help preserve the country’s famous Great Barrier Reef.

Corporate divers — all of whom know the reef intimately and, like so many companies, depend on its vitality — roam the seabed. There they collect broken pieces of coral and attach them to submerged frames on which the fragments can recover and grow. Eco-conscious tourists pay to see the unusual attraction.

It’s a strategy that, according to Senior Reef Guide Russell Hosp, aims to give “Mother Nature” a little boost. Around 30 gardens are currently being cultivated, and the healthy coral segments that thrive on their artificial underwater structures are then transplanted to damaged areas of the reef.

“Coral gardening” in underwater nurseries is trying to help preserve Australia’s famous Great Barrier Reef. (Video: Michael Robinson Chavez)

The Coral Nurture Program is just one of many projects along the Queensland coast, including one, run by the Reef Restoration Foundation, which has just seen its planted coral spawn for the first time. Together, these efforts aim to transform the reef by making it more resilient.

This month’s COP27 conference in Egypt discussed adaptation solutions for coral nations. Peter Thomson, the UN secretary general’s special envoy for the oceans, told a panel that he was convinced of the effectiveness of programs such as coral nurseries after seeing the results in his native country, Fiji.

The Great Barrier Reef has the most coral in decades. Global warming could reverse it.

“Don’t accept the idea that coral reefs are going to disappear,” he said. “We are going to refuse this future.”

However, none of these advances can overcome runaway global warming. “A 1.5 degree world is really the death knell for reefs,” warned Carol Phua, who leads the World Wildlife Federation’s Global Coral Reef Initiative.

The loss would be tragic. Corals are arguably the strangest of the many bewildering life forms that can be found in the world’s oceans, both animal, plant and mineral.

The animal is the polyp, a transparent creature with tentacles related to the anemone and the jellyfish. Coral polyps have spongy bodies but have evolved the miraculous ability to secrete calcium carbonate – the same material as limestone rock – as protection. These calcium carbonate barricades constitute the visible architecture of a reef.

Inside the polyp tissue is a living algae called zooxanthellae. It is these single-celled organisms that give reefs their famous rainbows of color. And, more importantly for the polyp, the algae provide food for their hosts, converting sunlight into proteins, fats and carbohydrates through photosynthesis.

Coral polyps have spongy bodies but have evolved the miraculous ability to secrete calcium carbonate, which is the visible architecture of a reef. (Video: Michael Robinson Chavez)

There are billions of coral polyps, containing tens of billions of zooxanthellae, hidden within the hard structure of the Great Barrier Reef. Each newborn polyp absorbs algae and secretes rock, adding immeasurably to an ecosystem that has been developing for 20,000 years.

One man’s lonely quest to save the world’s corals draws a sequel

The problem, said Emma Camp, co-founder of the Coral Nurture program and academic marine biologist, is that “corals have a narrow environmental niche, or range, that they generally like to survive.”

Coralline algae can only survive in warmer waters. But when the temperature gets too hot, the algae begin to emit a toxic substance instead of food, which the polyp instinctively and protectively ejects into the ocean.

The result is coral bleaching, and the striking images of reefs after an event show what corals look like without the algae inside. Unless the water temperature drops and the algae can safely return, the polyp starves and the reef remains colorless.

The Great Barrier Reef has seen four bleaching episodes in various sections since 2016. Even when a coral colony survives, stress takes its toll. Coral needs time to recover, and multiple bleachings in a short period are more likely to be fatal. Some species tolerate heat better than others, but when the most vulnerable species die, the diversity of the reef suffers.

The would-be ‘coral factory’ is restoring reefs destroyed by climate change

Coral Nurture participants have planted nearly 77,000 corals over the four years of the program. Camp acknowledged that compared to the vastness of the reef – the equivalent length from Florida to Maine – the number is small. “Where we are with most current restoration efforts is that they are local,” she said.

This focus is something Alan Wallish appreciates. He is a tour operator in Cairns who has spent several decades on the reef, and his company, Passions of Paradise, is one of five guiding companies partnering with University Scientists. The idea, he said, is “to take care of your own little patch.”

Other ongoing initiatives to maintain the reef run the gamut. Eye on the Reef, run by the Great Barrier Reef Marine Park Authority, appeals to the masses of divers who visit underwater to collect data while they are there. A “Coral IVF” project, led by Southern Cross University, collects coral sperm and eggs and fertilizes them in an ocean basin, depositing the larvae in degraded regions.

Native rangers from the Mandubarra people are also involved, working with recreational fishing group OzFish and researchers from James Cook University to plant seagrass meadows. In a lab near Townsville, specialists from the Australian Institute of Marine Science are experimenting with a molecule-thick biodegradable film that can block heat from entering the ocean.

The race to save Florida’s diseased corals

Climate change remains the big watchword for all these initiatives. Human intervention projects “are going to be essential” in the decades to come, said Scott Heron, an environmental physicist at the ARC Center of Excellence for Coral Reef Studies. But they will only be more effective if they progress in parallel with a rapid reduction in greenhouse gas emissions.

“We need to address climate change and the causes of climate change in a policy-consistent way, so that we don’t put a torch and a pipe on the fire,” Heron said.

Despite the odds, Hosp is actually quite optimistic as he guides visitors on the Great Barrier Reef. “The work we’re doing on the reef is in conjunction with the work being done in Antarctica and in Africa, all over the world,” he said. “There is this concerted effort to try to solve the problem in any way possible.”

“Quite honestly,” he added, “I think it’s a bit early to check the box and say that the reef, or any other ecosystem, is a lost cause. Because it’s absolutely not the case.

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