9 innovations in coral reef restoration

The coral reef, like the polar bear, has become a symbol of the devastating effects of climate change. The once colorful ecosystems that harbor a quarter of all marine species are rapidly shrinking due to heat stress, ocean acidification and water pollution. By 2021, half of the world’s coral cover had been lost since the 1950s, and researchers said a temperature rise of 2.7 degrees could increase that number to a catastrophic 70-90%.

Scientists are scrambling to find ways to save coral reefs, brainstorming and testing a range of strategies. Some are laborious, like propagation; others are very imaginative, such as the use of sound and electricity. Here are some of the most innovative coral reef restoration experiments of the century so far.

Cloud clearing


Australian researchers have developed a method called “cloud thinning” which involves creating clouds on coral by spraying microscopic marine particles into the sky using a turbine. The clouds eventually cast a shadow on the coral and cool the water temperature during heat waves, ultimately preventing coral bleaching.

The research team tested prototype filtering equipment at Broadhurst Reef in 2020. The experiment was a success and the team announced plans to test larger clouds over the next few years. years to come. By 2024, the researchers aim to test the technology’s impact on rainfall patterns to ensure it is a feasible method.

Acoustic enrichment

Healthy reefs are noisy places, but when damaged they go quiet. A group of scientists started playing the sounds of a healthy reef on a speaker in an unhealthy reef environment to see how the ecosystem would react.

In 2019, researchers from the University of Exeter, University of Bristol and James Cook University in Australia, as well as the Australian Institute of Marine Science, conducted an “acoustic enrichment ” of 40 days on a degraded section of the northern Great Barrier Reef. The number of fish in this reef has doubled and the number of species present has increased by 50%.

Assisted evolution

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Assisted evolution takes an organism’s natural evolutionary processes and accelerates them. Scientists around the world are working to apply this concept to coral to prepare it for the stressors of warmer, more acidic water that climate change will bring.

Assisted coral evolution takes many forms. One is stress conditioning, in which pieces of coral are exposed to sublethal conditions to increase their stress tolerance. Theoretically, they would then pass on these evolved traits to their offspring. Another method is being studied at the Australian Institute of Marine Science National Sea Simulatorwhere scientists interbreed coral species to grow a hybrid that can survive future conditions.

Spread in water

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Since 2010, The Nature Conservancy has been working in the Florida Reef Tract to breed new corals from healthy corals using in-water propagation. Coral fragments are taken from healthy colonies and placed in an underwater “nursery”. Here they grow safely and under the watchful eyes of scientists.

More cuttings are eventually taken from the coral to grow more clones until pieces are eventually replanted on damaged reef sites to hopefully recolonize the reef on their own.

In 2019, there were more than 50,000 corals housed in underwater nurseries and some 10,000 planted on damaged reefs. Today, more than 30 countries use water propagation, from Hawaii to Thailand.


Some corals grow slowly. The brain coral, for example, only grows a few millimeters per year. Targeted specifically at slow-growing corals, a technique developed by Mote Marine Laboratory called “reskinning” takes micro-fragments of rocky corals and mounts them on bleached dead coral bases. The baby corals grow and cover the surface of the old coral.

Because coral reproduction is dependent on size rather than age, young corals mature in less time and may begin to reproduce earlier than corals grown from scratch.

Through an organization called the Plant a Million Corals Foundation100,000 corals were planted using the reskinning method.

heat resistant algae

Coral and algae have a symbiotic relationship, but as the water temperature rises, the algae collapses and leaves its coral host vulnerable to bleaching.

In 2017, Saudi researchers sought to help algae adapt to heat stress, which would encourage them to stay with the coral and continue to provide nutrients. This would involve replicating and mutating genetic sequences called retrotransposons, also known as “jumping genes”, to make algae more heat tolerant.

The experience was successfully replicated in Australia in 2020. Today, researchers are testing algal strains in adult colonies across a range of coral species.

Biorock technology

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Biorocks use electricity to restore coral. These steel-framed structures send low electrical voltage through the seawater, causing a chemical reaction that coats the coral with calcareous minerals similar to the natural coating of young coral.

The nonprofit Global Coral Reef Alliance says biorock reefs help accelerate coral growth and make them more resilient to temperature spikes and acidity.

The current is safe for humans and animals, and the structures are not limited in size. “They could be grown hundreds of miles long if funding allowed,” says the Gili Eco Trustresponsible for setting up more than 150 biorock structures in Indonesia.

Gene storage banks

If (the worst case scenario) the world were to lose many or all of its corals in the next 50 to 100 years, a repository of their genetic information would be the only chance for restoration. The Smithsonian Conservation Biology Institute pioneered this effort using cryopreservation, i.e. freezing coral sperm.

The sperm the institute has frozen so far is stored at around -265 degrees Fahrenheit in banks at the USDA’s National Animal Germplasm Program and at Taronga Zoo in Australia. By 2021, 37 coral species had been cryopreserved around the world.

Assisted genetic migration

By freezing coral sperm, scientists can also migrate coral species that would otherwise remain both geographically and genetically isolated. The same group that pioneered cryopreservation at the Smithsonian Conservation Biology Institute is also leading the charge on migration. Genes from different populations are mixed to make the hybrids more resistant to bleaching.

In 2021, the team reported that new corals from a Caribbean species had been thriving for two years in Florida under human care.

What can you do to help coral reefs?

There’s room for everyone in the fight to save coral reefs, not just scientists with diving credentials. Here’s how you can help protect these beautiful and extremely important keystones of the ocean.

  • Always wear coral reef-safe sunscreen, not just when you’re at the beach. Chemicals (namely oxybenzone and octinoxate) that were once common in conventional SPFs have been shown to exacerbate whitening. Be sure to use mineral sunscreens made with zinc oxide or non-nano titanium dioxide, which are considered safe by the National Oceanic and Atmospheric Administration.
  • Pay attention to your plastic use and waste. Plastic pollution is rampant in the ocean, and it’s one of the main causes of coral reef decline.
  • Tourism can harm coral reefs. If you happen to be nearby and fancy a visit, choose a company that does so responsibly and preferably gives back to the reef. This means there is no mooring on the reef, requiring reef-safe sunscreens and teaching tourists not to touch the reefs.
  • Avoid fertilizers and pesticides at home. Yes, even if you live hundreds of miles from the coast, the chemicals you put on your lawn end up in the oceans. Make sure all lawn and garden treatments are natural and safe for the environment.
  • Volunteer or donate to reef conservation and restoration organizations like the Coral Restoration Foundation, Coral Reef Allianceor the Oceans Conservation Trust.
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