Helping Coral Revive, Survive and Thrive

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Corals can be “planted” — attached to reefs piece by piece with cement, zip ties, and nails

Jennifer S. Holland wrote in National Geographic: As global temperatures trend up, some scientists have taken to prepping — stashing hard corals in “living biobanks” to conserve as much diversity as possible. A holding facility in Sarasota, Florida, is already accepting U.S. specimens, while the nonprofit Great Barrier Reef Legacy and its partners have established the Living Coral Biobank in Australia, where a seaside “ark” will house the more than 800 hard-coral species from around the world.“This is something we can do right now: Collect every species and tag them and keep them alive indefinitely, for genetic studies and, if possible, to repopulate the oceans with species extinct in the wild sometime in the future,” Charlie Veron, one of the biobank’s founders, told National Geographic. “It’s up to us to use every tool we have to keep reefs alive. My belief is, we can’t not do this.” [Source: Jennifer S. Holland, National Geographic, April 7, 2021]

In February 2017, Ove Hoegh-Guldberg helped launch an initiative called 50 Reefs, aiming to identify those reefs with the best chance of survival in warming oceans and raise public awareness. His project partner is Richard Vevers, who heads the XL Caitlin Seaview Survey, which has been documenting coral reefs worldwide. "For the reefs that are least vulnerable to climate change, the key will be to protect them from all the other issues they are facing — pollution, overfishing, coastal development," said Vevers, who founded The Ocean Agency, an Australian organization seeking new technologies to help mitigate some of the ocean's greatest challenges. If the reefs remain healthy and resilient, "they can hopefully become the vital seed-centres that can repopulate surrounding reefs." [Source: Associated Press, March 13, 2017]

Nature itself is providing small glimmers of hope. Some corals, for example, are showing tentative signs of a comeback. But scientists don't want to leave it to chance, and are racing ahead with experiments they hope might stave off extinction. "We've lost 50 percent of the reefs, but that means we still have 50 percent left," said Ruth Gates, director of the Hawaii Institute of Marine Biology. who is working in Hawaii to breed corals that can better withstand increasing temperatures. "We definitely don't want to get to the point where we don't intervene until we have 2 percent left." Going a step further, she is also trying to "train" corals to survive rising temperatures, exposing them to sub-lethal heat stress in the hope they can "somehow fix that in their memory" and survive similar stress in the future. "It's probably time that we start thinking outside the box," Gates said. "It's sort of a no-win game if we do nothing.

Websites and Resources: National Oceanic and Atmospheric Administration (NOAA); Smithsonian Oceans Portal ; Woods Hole Oceanographic Institute ; Monterey Bay Aquarium ; MarineBio ; Websites and Resources on Coral Reefs: Coral Reef Information System (NOAA) ; International Coral Reef Initiative ; Wikipedia article Wikipedia ; Coral Reef Alliance ; Global Coral reef Alliance ;Global Coral Reef Monitoring Network

Helping Coral Reef Revive

hanging corals at a coral nursery

Scientists have proposed some measures that can be put into place to help the ailing reefs. Among these are removing stressors such as fishing and tourism, and helping coral migrate to more suitable environments. But they stress that such measures may only be beneficial in the short term, and that for a lasting positive impact, global warming must be addressed, and quickly.[Source: Li Cohen, CBS News, February 3, 2022]

Measures taken by human to repair reefs include using metal rods to hold up broken pieces of coral in place, and clearing away debris, and sediment. Researchers are experimenting with transplanting coral and introducing new species to new areas.

The U.S. National Oceanic and Atmospheric Administration (NOAA) runs programs that breeds elkhorn corals in nurseries and replants them into the wild. It also 1) increasing elkhorn coral resilience to climate change; 2) rescuing injured elkhorn corals after ship groundings or major storm events; 3) tracking individuals over time to understand population trends and causes of death; 4) conducting spawning observations and collection of eggs and sperm for culturing elkhorn coral larvae; 5) conducting temperature and acidification experiments on eggs, sperm, larvae, and newly settled colonies; and conducting experiments to enhance the success of elkhorn coral propagation efforts. [Source: NOAA]

Reefs can revive themselves in as little as five years as was the case with a reef off Banda Indonesia that was completely destroyed by lava from an eruption. Jennifer S. Holland wrote in National Geographic: Encouragingly, in some instances corals already are doing the job themselves: Scientists working on reefs around the world’s largest atoll — Kiritimati in the central Pacific — discovered corals that were recovering from bleaching during a heat wave. They did it by taking in naturally heat-tolerant algae. These comeback corals, however, weren’t in crisis from other human-caused stresses when they bleached; those that had been stressed previously did not recover as well, illustrating the devastating impact of a one-two punch. Still, it’s a hopeful sign that scientists hadn’t seen in the wild. [Source: Jennifer S. Holland, National Geographic, April 7, 2021]

Scientific Efforts to Help Coral Grow

Scientists are also scrambling to protect vulnerable areas and develop hardier species. Fernando G. Baptista, Lawson Parker and Eve Conant wrote in National Geographic: Many conservation efforts are under way to help ailing reefs, but two reef-repopulating methods improve the odds for large-scale restoration. Both methods start with collection Divers cut or gather fragments from live corals. Eggs, sperm, and larvae are captured during spawning events. [Source: Fernando G. Baptista, Lawson Parker and Eve Conant, National Geographic, April 15, 2021]

planted corals in the Maldives after six months

Ken Nedimyer, a Florida-based research scientist who got his start in the aquarium business, has a nursery with a variety of coral strain, growing under different conditions. He is experimenting with taking bits of live coral and glueing them to different surfaces. He told the New York Times, “We tried a lot of epoxy. We found kinds that stick to wet suits, to hair, to cameras” They finally settled in an epoxy glue used by taxidermists which hold firm in water and is white so it doesn’t look bad.”

Jennifer S. Holland wrote in National Geographic: In a lab at the Australian Institute of Marine Science, geneticist Madeleine van Oppen is giving a push to the natural adaptations that could reduce such losses. By teasing out genes related to heat management in algae and bacteria that live in corals, she says, “we are starting to have a good understanding of these intimate associations and to make use of them.” By exposing this lab-grown algae to stepwise temperature bumps over years, she lets natural selection and random mutation do the work of boosting the algae’s heat tolerance — but on a fast track. Corals that accept these experimentally evolved algal partners have proven less prone to bleaching. Van Oppen also plans to “lab evolve” the bacteria that live in coral microbiomes. “If we could inoculate coral with lab-grown algae and bacteria that can help neutralize heat stress,” she says, “we see the potential to increase thermal bleaching tolerance in the wild.” [Source: Jennifer S. Holland, National Geographic, April 7, 2021]

The institute’s scientists are also creating hybrids, crossing corals adapted to warmer waters with cool-water ones of the same species to see if heat tolerance is passed to the offspring. The initial results are promising. “And we are creating hybrids between species, which can have enhanced climate resilience compared to their purebred counterparts,” van Oppen says.

Planting Resilient Coral

According to the BBC: Some scientists believe Red Sea coral could hold the secret to saving coral around the world. One of them, oceanographer Sylvia Earle, says more research is needed to find out what makes this coral less vulnerable to rising temperatures. But she says it is of "enormous importance to the international community because of the possibility of transplanting corals from the Red Sea to rehabilitate the degraded reefs in other parts of the world, like the Great Barrier Reef". [Source: Ziad Al-Qattan — BBC News Arabic, November 16, 2022]

Jennifer S. Holland wrote in National Geographic: Mountainous star corals — Orbicella faveolata, listed as threatened under the Endangered Species Act — were cultivated and “planted” in 2015 by Hanna Koch and her colleagues from the Mote Marine Laboratory & Aquarium as part of a reef restoration effort. The corals survived a bleaching event that year, a Category 4 hurricane in 2017, and a disease outbreak two years later, demonstrating heartening resilience. They reached reproductive maturity years faster than their wild counterparts, and they became the first restored boulder-forming corals to spawn at sea.[Source: Jennifer S. Holland, National Geographic, April 7, 2021]

Site 120 coral reef in Tallaboa, Puerto Rico in 2006 after an il tanker grounding damaged a reef there

For decades ecologists have been honing this strategy for fast-growing branching corals. But until recently, few ocean farmers tried cultivating the real building blocks of a reef — such as boulder and brain corals, slow-growing giants that can live for centuries and take decades to reach reproductive maturity. Then came a breakthrough: Mote scientists discovered that “microfragments” sawed off these corals act a bit like wounded skin, growing extremely quickly — some 10 times faster than larger cuttings. Grown side by side in lab aquariums, polyps from the same colony will fuse, reducing the time needed to reach reproductive size. Raised this way, some species that typically take a decade or more to mature have begun spawning in just a few years.

Even the best tended garden isn’t immune to bad weather, and many nursery-grown branching corals eventually have succumbed to heat. So it’s critical, says Mote senior biologist Erinn Muller, to focus on corals with high heat tolerance. Muller is also studying whether there’s a link between temperature and a disease called stony coral tissue loss, which first appeared in the Florida Keys in 2014 and now has affected nearly every part of the 360-mile-long barrier reef. “Disease is a chronic problem for corals, so we screen for disease tolerance as well as heat tolerance and ramp up reproduction of those most likely to survive both in the coming decades,” she says. “That way we integrate resilience right into our restoration pipeline.”

Mote’s strategies also support reef recovery beyond Florida’s waters. Raising Coral Costa Rica — a team led by local and American coral reef ecologists — is both farming branching species and microfragmenting boulder species to revive ancient reefs in Golfo Dulce. These corals, some of them thousands of years old, are of particular interest: With the gulf fed by four rivers and flushed by tides, they are exposed to quick fluctuations in temperature, acidity, and salinity — making them well equipped to handle changing conditions. Their genes, and those of corals living in similarly fickle conditions, could hold clues for bolstering resilience elsewhere.

Helping Coral Spawn

Jennifer S. Holland wrote in National Geographic: On the other side of the globe, Marine ecologist Peter Harrison of Australia’s Southern Cross University knows that no matter how genetically outstanding a coral’s parents, any single larva has only about a one-in-a-million chance of surviving. He wants to improve those odds dramatically. “Larvae have limited control over where they go,” he says. The vast majority drift away, and if they do eventually bump into suitable substrate, he notes, there’s “a wall of mouths waiting to eat them.” [Source: Jennifer S. Holland, National Geographic, April 7, 2021]

Site 120 in 2015: Restorers stabilized rubble, reattached broken corals and rebuilt the reef with coral transplants from nurseries, Nursery-grown corals can be used not only to help reefs damaged by groundings, storms or pollution but those harmed by changing ocean conditions as well

So Harrison’s teams scoop up slicks of eggs and sperm released by corals that have survived bleaching and proven their heat tolerance. Amassing the gametes in mesh enclosures near the ocean surface promotes fertilization and larval formation; those offspring can then be drizzled over damaged reefs. Harrison is testing two distribution methods: remote-controlled “LarvalBots” that squirt larvae onto reefs and ceramic plugs with larvae attached that can be stuck into gaps in the reef.

Targeted larval settlement has proven effective on research plots in the Philippines and on the Great Barrier Reef, but Harrison knows he needs to scale way up, spreading billions of larvae over miles of seafloor to make a difference.

The spawning events at which Harrison pilfers gametes are one of nature’s ways of maintaining strong genetic diversity — as eggs and sperm from different parents mingle. But as reef health declines, fewer corals are spawning successfully. After the 2016 and 2017 bleaching events on the Great Barrier Reef, Hughes and colleagues found that larval colonization had dropped 89 percent.

Transporting Coral to New Locations

According to National Geographic: Fragments can be used to generate new colonies to rebuild reefs, but the clones that result don’t add to genetic diversity. Assisted reproduction produces new genetic individuals, some with enhanced resilience to increasingly harsh conditions. Speeding natural selection by exposing corals to stress and modifying symbiotic algae may enhance traits such as tempera- ture tolerance. Raising new coral by fragmentation is labor-intensive, requiring repeated manual handling of each coral, but it is the most common approach.Field-based nurseries are less costly than those on land but are vulnerable to environ- mental threats. Fragments are trans- planted by hand to a reef, secured with items such as biodegradable epoxy, nails, and cable ties. [Source: Fernando G. Baptista, Lawson Parker and Eve Conant, National Geographic, April 15, 2021]

Transporting corals from nurseries to reefs is often the most expensive, labor-intense part of restoration, an obstacle to large-scale reef restoration. Assisted reproduction produces new genetic individuals, some with enhanced resilience to increasingly harsh conditions.

Coral larvae attach to hard surfaces where they are able to mature under observation. Tetrapod-shaped seeding units that wedge into the reef eliminate the need to transplant each baby coral by hand. Larvae dispersed directly over a reef are temporarily covered to keep them in place and aid attachment.

What We Can Do to Help Coral Reefs

Even if you live far from coral reefs, you can have an impact on reef health and conservation. Things you can do to protect coral reefs include: 1) Conserve water. The less water you use, the less runoff and wastewater that will eventually find its way back into the ocean. 2) Volunteer in local beach or reef cleanups. If you don't live near the coast, get involved in protecting your watershed. 3) Become an informed consumer and learn how your daily choices such as water use, recycling, seafood, vacation spots, fertilizer use, and driving times can positively (or negatively) impact the health of coral reefs. 4) Choose sustainable seafood. Learn how to make smart seafood choices at [Source: NOAA; [Source: Jennifer S. Holland, National Geographic, April 7, 2021]

There are also many things you can do to ensure that you are environmentally conscious when you visit coral reefs or coastal areas. These include things such as hiring local guides to support the economy, removing all trash from an area, never touching or harassing wildlife in reef areas, and avoiding dropping your boat anchor or chain nearby a coral reef. Many organizations are working to save or restore coral reefs, including the National Geographic Society’s Pristine Seas project. Check their websites to see how to donate or to find volunteer opportunities either on land or at sea.

Energy efficient light bulbs and driving less reduce greenhouse gas emissions. Climate change is one of the leading threats to coral reef survival. Be a marine crusader. In addition to picking up your own trash, carry away the trash that others have left behind. Don't send chemicals into our waterways. Nutrients from excess fertilizer increases algae growth that blocks sunlight to corals. Apply fertilizers and pesticides sparingly. Pick up after your pets. Wash your car on your lawn. Dispose of lawn clippings in a compost pile. Harvest rooftop rain water through rain barrels or rain gardens. DO NOT dump paint, oil, antifreeze, debris, or other household chemicals into street gutters or storm drains. Clean up spilled brake Fluid, oil,greaseand antifreeze Maintain proper septic system function with inspections and pumpouts every 3-5 years.

Coral-Reef Friendly Boating, Swimming, Diving and Fishing

Practice safe boating. Anchor in sandy areas away from coral and sea grasses so that the anchor and chain do not drag on nearby corals. Obey aids-to-navigation and signage to make sure you do not accidentally injure corals that are just below the surface. When swimming or diving on a reef, don’t touch the coral and don’t disturb the other marine life. Coral reefs are alive. Stirred-up sediment can smother corals. Choose dive operations that protect reefs by practices such as tying up to a mooring buoy rather than anchoring, which can cause damage to reefs.

Choose sunscreen with zinc oxide or titanium dioxide over those containing oxybenzone, which is toxic to corals. Consider covering up with a long-sleeved shirt or a rash guard to minimize sunscreen use, and look for reef-friendly sunscreens that are less harmful to marine life. Check sunscreen active ingredients. Seek shade between 10 am and 2 pm, use Ultraviolet Protection Factor (UPF) sunwear. For more information, visit

In regards to fishing only take what you need. Catch and release fish that you don't plan to eat. Be a responsible aguarium owner. Know where your fish come from and DO NOT release unwanted fish into the wild. Educate yourself on local fishing rules and regulations. Your state fishery agency or bait and tackle shop can help you learn more.

Reef Tips for Divers, Snorkelers and Swimmers:
1) Maintain natural buoyancy to avoid knocking or brushing against coral and marine life.
2) Coral is alive and easily damaged. Avoid touching, grabbing or standing on coral.
3) Please watch your fin wash. Sand can injure or smother small creatures and coral.
4) The underside of rocks are home to small creatures that can not live anywhere else. Please leave rocks, shells and coral in place for the reef dwellers who need them.
5) Killing, damaging, riding or chasing are examples of poor diver behavior.
6) Trash can kill marine life. Please collect any trash you see on the beaches or in the water.
7) Feeding fish can make them pests, and some may even aggressive toward divers.
8) Use a permanent mooring buoy to secure your boat instead of dropping an anchor.
9) Do not collect live shells.

Don’t Buy Products Made with Coral or Sea Creatures

Avoid buying souvenirs or jewelry made from coral or any other sea creature. Corals are popular as souvenirs, for home decor and in costume jewelry. The U.S. is the world's largest documented consumer of Corallium, red and pink corals often used to create jewelry. Finished pieces of jewelry and art crafted from this type of coral can fetch anywhere between $20 and $20,000 in the marketplace. Continued consumer demand is contributing to the decline of these delicate corals around the world. [Source: NOAA]

Commercial harvesting to satisfy the demand for coral jewelry has reduced colony size, density, and age structure of Corallium over time. Harvesting is also lowering the reproduction capability of this species and is decreasing its genetic diversity. Research indicates that removal of red and pink corals for the global jewelry and art trade is also leading to smaller and smaller Corallium in the wild.

Corals grow very slowly, are extremely long-lived, and take years to reach maturity. It takes corals decades or longer to create reef structures. Once coral is harvested — especially when it's extracted at a young age — surrounding coral beds often do not recover. That's why it's best to leave corals and other marine life on the reef. Remember: corals are already a gift. Don't give them as presents.

When it comes to coral jewelry, there is one exception to the rule. Black coral from Hawaii is the only coral that is legally harvested in the U.S. This fishery is carefully managed by the state of Hawaii and the federal government to ensure that this species of coral is not overexploited. State certified divers use sustainable harvest techniques to harvest black corals — the official gemstone of Hawaii — to produce precious coral jewelry.

Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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