Worldwide coral reefs are suffering from the impacts of climate change. Around the world researchers are pioneering ways to protect and restore coral reefs that have already bleached. Between these efforts and the amazing capacity for corals to adapt to healthier environments, there seems to be some hope.
Worldwide coral reefs are suffering from the impacts of climate change. When the ocean is too warm for microscopic algae to live in coral tissue leave and the corals bleach.
Algae provides corals food. Without it, they bleach and become very unhealthy. Most corals die.
You have probably seen images of huge swaths of the Great Barrier Reef that have bleached. It is a tragedy affecting all the animals and people that are dependent on healthy reefs. “Coral reefs provide food and income through tourism, fisheries, and shoreline protection—valued at tens of billions to trillions of dollars each year globally.” The world needs to drastically cut our C02 emissions to slow climate change. Unfortunately, the ocean is already underway and will continue for a long time. This is why we need to both reduce CO2 emissions and help restore coral reefs NOW.
Restoration by growing, gardening and outplanting
Around the world researchers are pioneering ways to protect and restore coral reefs that have already bleached. Interventions can take many forms including taking fragments of coral, growing, gardening and outplanting them; to harvesting millions of naturally-produced eggs and sperm that create millions of new individual coral larvae. Along with the specific techniques for creating more corals for reefs, scientists are monitoring growth and ecosystem health, and characterizing the genetics of outplanted coral to make sure there is diversity and therefore, resilience.
Scientists are trying to restore and rebuild bleached coral reefs by transplanting healthy corals onto ailing or dead corals. The general method is to find or break off a fragment of coral to grow in an underwater nursery or in a lab. Once the coral fragments have grown large enough—after six to tenth months—scientists outplant them onto the reefs. The corals are attached to the skeletal structures of dead or dying corals, using cement, zip ties and nails.
Looking at the big picture, scientists see reef restoration as a strategy to save the diverse ecosystem services that coral reefs provide. Researchers share data about growth rates and reproduction, something that doesn’t always happen in science. They’re trying to help each other increase the efficiency and scale of growing and restoring corals.
One of the pioneers of this method, Dr. David Vaughan at Mote Marine Lab in Florida, found that corals grown in lab nurseries grow 25-50 times the rate they grow in nature. Researchers from around the world have gone to Mote to learn the techniques.
Restoration by spawn and raising corals from larvae
Some researchers working on the Great Barrier Reef are growing corals starting with collecting eggs and sperm, called spawn. When corals spawn, their eggs and sperm form slicks in the ocean. This involves collecting the slick “floating enclosures and towing them short distances to adjacent, high-priority areas for release. The aim is to increase the number of corals from the spawning slick that are ultimately recruited into reef populations.”
Another approach to growing new corals is to raise corals from larvae to adult in a lab, return them to an ocean nursery environment to grow more, and then return them to the wild. When corals in established underwater nurseries spawn, researchers collect the eggs and sperm and take them to a lab on land where they’re mixed together to assist in fertilization. When the young corals reach a size to attach to a growing structure, they are moved to the nursery and then eventually outplanted.
The new corals, like those described above, are created sexually, as opposed to those created asexually by microfragmentation. The advantage of these two methods is guaranteeing genetic diversity through sexual reproduction. It gives the hope of restoring the genetic diversity and resilience of corals reefs.
Researchers are studying corals that are more heat tolerant to tease out the what’s behind that tolerance. With this knowledge, scientists can grow species that might survive bleaching events and outplant them into healthy habitats.
For all of the interventions, it’s essential to monitor success, and set global standards. Success may have several aspects including: scale, good growth rate in nurseries, success in outplanting, reproductive success and diversity, and overall ecosystem health.
Through a symbiotic collaboration between five tourism companies and marine scientists at the University of Technology Sydney, “coral gardening” in underwater nurseries is trying to help preserve the country’s famed Great Barrier Reef.
Divers for the companies — all intimately acquainted with the reef and, like so many businesses, dependent on its vitality — scour the seafloor. There they collect broken pieces of coral and attach them to submerged frames on which the fragments can recover and grow. Ecologically minded tourists pay to see the unusual attraction.
It’s a strategy that master reef guide Russell Hosp says is aimed at giving “Mother Nature a little bit of a boost.” Some 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.
The Coral Nurture Program is just one of numerous projects along the Queensland coastline, including one, run by the Reef Restoration Foundation, that just saw its planted coral spawn for the first time. Together, these efforts aim to transform the reef by making it more resilient.
This month’s U.N. Climate Change Conference in Egypt, known as COP27, discussed adaptation solutions for coral nations. Peter Thomson, the U.N. secretary general’s special envoy for oceans, told a panel that he was a convert on the effectiveness of programs such as coral nurseries after seeing the results in his native Fiji.
“Don’t accept the idea that coral reefs are going to be extinct,” he said. “We’re going to refuse that future.”
None of the progress can overcome unchecked global warming, however. “A 1.5-degree world is really a 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, simultaneously animal, vegetable and mineral.
The animal is the polyp, a transparent, tentacled creature related to anemone and jellyfish. Coral polyps have squishy bodies but have evolved the miraculous ability to secrete calcium carbonate — the same material as limestone rock — as protection. These calcium carbonate barricades make up the visible architecture of a reef.
Inside the polyp’s tissue are a living algae called zooxanthellae. It’s these single-celled organisms that lend reefs their famous rainbows of color. And, more importantly for the polyp, the algae provide food for their hosts, turning sunlight into proteins, fats and carbohydrates through photosynthesis.
Coral polyps have squishy bodies but have evolved the miraculous ability to secrete calcium carbonate, which makes up the visible architecture of a reef. (Video: Michael Robinson Chavez)
There are billions of coral polyps, containing tens of billions of zooxanthellae, hiding within the hard structure of the Great Barrier Reef. Every newborn polyp absorbs algae and secretes rock, adding infinitesimally to an ecosystem that has been growing for 20,000 years.
The problem, said Emma Camp, the Coral Nurture Program’s co-founder and a university marine biologist, is that “corals have a narrow environmental niche, or range, that they typically like to survive.”
Russell Hosp, a master reef guide, notes his observations along the Great Barrier Reef on Hastings Reef. (Michael Robinson Chavez/The Washington Post)
Coral algae can only survive in warmer waters. But when the temperature gets too warm, the algae begins emitting a toxic substance instead of food, which the polyp instinctively and protectively ejects into the ocean. The result is coral bleaching, and the stark images of reefs after an event show what corals look like without 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 experienced four bleaching events in various sections since 2016. Even when a coral colony survives, the stress takes a toll. The coral needs time to recover, and multiple bleachings in a short period are more likely to be fatal. Some species cope with heat better than others, but when the most vulnerable species die, the reef’s diversity suffers.
Coral Nurture participants have planted nearly 77,000 corals in the program’s four years. Camp acknowledged that in comparison to the reef’s vastness — the equivalent length of Florida to Maine — the number is small. “Where we’re at with most current restoration efforts is that they’re local,” she said.
That focus is something Alan Wallish appreciates. He’s a tour operator in Cairns who has spent several decades on the reef, and his business, Passions of Paradise, is among the five guiding companies partnering with the university scientists. The idea, he said, is “about looking after your own little patch.”
The other initiatives underway to nurture the reef run the gamut. Eye on the Reef, headed by the Great Barrier Reef Marine Park Authority, enlists the masses of divers who sightsee underwater to collect data while they’re there. A “Coral IVF” project, led by Southern Cross University, gathers coral sperm and eggs and fertilizes them in an ocean pool, depositing the larvae in degraded regions.
Indigenous rangers of the Mandubarra people are also involved, working with the recreational fishers group OzFish and researchers from James Cook University to plant sea grass meadows. At a lab near Townsville, specialists at the Australian Institute of Marine Science experiment with a biodegradable, molecule-thick film that may block heat from entering the ocean.
Climate change remains the big caveat for all these initiatives. Human intervention projects “are going to be essential” in coming decades, said Scott Heron, an environmental physicist with the ARC Centre for Excellence for Coral Reef Studies. But they will be most effective only if they advance in tandem with a rapid decrease in greenhouse gas emissions.
“We need to be addressing climate change, and the causes of climate change, in a policy-coherent way so that we’re not putting a blowtorch as well as a hose onto the fire,” Heron said.
Despite the odds, Hosp is actually pretty optimistic as he guides visitors on the Great Barrier Reef. “The work we’re doing on the reef is in conjunction with work being done in the Antarctic, and in Africa, all over the world,” he said. “There’s this concerted effort to try and fix the problem in as many ways as we can.”