When I was 7 years old, I traveled to the Florida Keys with my grandmother and learned to snorkel, spending most of the day, every day, for over a week, peering down at countless corals bursting in indescribable shapes and glorious colors.
Nearly 30 years later, I returned to the same beaches, eager to strap on my mask and dive in. I was excited to show my West Coast-raised partner the beauty I knew to be hidden beneath the gentle aquamarine surface.
But there was no color left. Dead grey coral bodies, bleached out, drifted listlessly like the ghosts they were. A few colorful fish still darted around, but I ended up floating above them, tears filling my snorkel mask. What I had remembered from my own childhood was gone.
I can only hope the coral I grew up with and loved is not gone forever. But corals are fighting an uphill battle. About 20 percent of global corals that once lived are gone. Parts of Australia’s Great Barrier reef have lost more than 70 percent of their corals as of 2016. In the Florida Keys, paleoecologists have used detailed nautical maps dating back to the 1700s to determine that in the past 240 years, about half of the coral has disappeared—for areas closer to shore, 90 percent or more is gone.
Part of the reason for this decline is that corals have to contend with several big threats. “Fishing has an impact; gear, like lobster and crab traps have direct impacts on [the reef],” Chris Bergh, the South Florida conservation director for The Nature Conservancy, said. Bergh adds that well-enforced coral-protection rules, like those in Florida—and especially as part of marine protected areas and national parks—go a long way toward minimizing these issues. “But local legal protections don’t help with global warming or water quality,” said Bergh. Pollution from farms, lawn chemicals, and sewage that make their way into the ocean, even from inland areas, washes over corals and weakens them. And warming seas deliver another blow: Higher water temperatures stress the corals leading them to “expel the symbiotic algae living in their tissues, causing them to turn completely white,” according to NOAA. Coral bleaching doesn’t equal dead coral, but it weakens them so much—just like pollution does—that it’s easy for disease to move in and deal the final death blow.
In response to this decimation of corals worldwide, researchers are desperately trying some new techniques to deal with the problem. With the longest track record of any of the coral restoration efforts, in-water propagation has been used successfully since the early 2000s, particularly for fast-growing, “weedy” corals like staghorn and elkhorn. It’s important to restore these corals because “as time passes, they become the foundation upon which slower-growing species attach themselves and grow and thrive,” said Bergh. Since their natural propagation strategy involves corals fragmenting and then drifting in the water column—to then take root in a new location—people can speed up the process by doing some of this work by hand. Coral restoration specialists take pieces of carefully harvested staghorn coral carefully and outplant them in open areas. In Dry Tortugas National Park, staghorn corals planted this way have an average 90 percent survivorship rate after a year.
While some of these newly planted corals were lost in Hurricane Irma, devastating parts of the Caribbean and the eastern coast of Florida, “even if they are lost, there’s potential that they will travel and stabilize somewhere else,” Jennifer Stein, the South Florida marine conservation coordinator for The Nature Conservancy, said.
Some corals take a lot longer to grow than staghorn and elkhorn corals; boulder corals (think brain coral) can take 50 years to reach sexual maturity, and can live to be 900 years old. Their slow growth and rounded structure provides great protection from predators and hurricanes, but they are still subject to the forces that cause bleaching events.
Importantly, scientists have discovered that it’s not the age of a coral that allows it to reproduce, but size. In a technique called micro-fragmentation, a small part of one of the larger boulder corals is grown and then attached to an older, bleached out base. “These fragments planted in arrays will grow together, merging to form one large colony rather than several small colonies,” according to a 2014 paper by Christopher Page, an ecologist at Mote Marine Laboratory in Sarasota, Florida, and one of the leaders in this technique. Once the new, live corals grow large enough to cover the dead coral (which might take hundreds of years to grow naturally to that size), they reach maturity faster and start reproducing. If successful in the field, where it’s currently being tested (it’s a very new technique), this reef-skinning could be a way to restore coral ecosystems with corals of various types, not just the fast-growing kind.
In what’s been called a “game-changer” for coral restoration, there’s also the very new technique that’s basically IVF for corals. It involves working with corals’ natural process of sexual reproduction. In the wild, corals release eggs or sperm into the water column, where they are subject to drift and wave action. They may meet to make a new baby coral—but most of the time they don’t. And even when egg meets sperm, often the coral larvae end up too far from the protection of the reef and die. It’s not the most efficient way to reproduce. But if we can induce captive corals to spawn, and then match eggs and sperm, a large number of coral larvae can be created, and then released en masse directly where they need to go.
And it seems like this works. In 2013, on a blast-damaged reef in the Philippines, a breeding coral population was successfully re-established. “The really exciting outcome is that surviving corals grew fast enough to get to a big enough size to start sexually reproducing themselves after three years,” professor Peter Harrison of Southern Cross University in New South Wales, told News Corporation Australia.
Scientists in Florida are following this work closely, and seeing other benefits to propagating new corals from resilient ones: “Within any of these coral species there are many genotypes,” said Bergh. “Some are adapted to hotter, cooler, clearer, or murkier water. What we have to work with are corals that have been through bleaching, disease, and hurricanes. The ones we’re working with are genetically tough—that’s important.”
Why is all this trouble being taken to restore corals? Reefs filled with colorful anthozoans gently swaying in the waves aren’t just beautiful tourist attractions—they are hotspots for biodiversity. “A quarter of all marine fish species reside in coral reefs and 500 million people depend on these ‘underwater rainforests’ for their livelihood,” according to the Worldwatch Institute. Like so many environmental stories, when we talk about “saving corals” it’s important to remember that we’re also saving human lives—and livelihoods.