A coral is an animal that demands imagination. Look closely through a dive mask (or a Google image search) and you’ll see that a coral reef’s rocky undulations are coated in an astonishing skin of tiny creatures that look like upside-down jellyfish, bells rooted in place, mouths open and ringed with tentacles waving to the sea. These are coral polyps. And right now, around the planet, they are dying with breathtaking speed. It’s uncertain how many will survive into the near future, and unclear what we can do to make sure they survive.  

Often mistaken for plants, corals are cousins to jellyfish and sea anemones, with whom they share a phylum and a distinctive physique. Each coral polyp is shaped like a tube, with a mouth, a simple stomach, and a base where it secretes a cup-shaped exoskeleton of calcium carbonate that roots it in place and protects it from predators. Many corals reproduce asexually, when polyps clone themselves. As new polyps form, they build their cup-shaped skeletons on top of the empty shells of previous generations, creating limestone reefs as they go. A single coral is often an animal composed of hundreds or thousands of interconnected polyps, a colony of genetic clones that share a single set of DNA, clinging to the skeletal remains of its own past dead.

Most corals are also hermaphroditic spawners, which means that in addition to cloning, they produce both eggs and sperm. One night a year, in a wildly improbable mass-spawning event, all the coral of a single species will release eggs and sperm bundled together into tiny translucent globes that cloud the water and rise to the ocean’s surface. Here, the globes break apart, sperm and eggs intermingle, and baby coral larvae are born. Researchers used to think a larva would float along helplessly, tossed by ocean currents, until it happened on a place to land. But in recent years researchers have discovered that a baby coral polyp can sense light, temperature, pH levels, and even sound in the ocean through which it navigates, waving its tiny cilia and swimming in search of a future home. Once a larva lands and attaches, it stays put for life.

3D-printed reefs, a new addition to the growing assortment of artificial reefs being dropped into ailing oceans worldwide, are designed with these polyps in mind, their nubbly surfaces grooved and inviting, intended to offer safety and succor. The world’s first 3D printed reef was sunk in the Persian Gulf in 2012. Made of pale sandstone with nubbly branches designed to look like actual coral, it was just one artificial unit among 2,620 (the others made of molded concrete) dropped off the coast of Bahrain in a massive effort to replenish dwindling fish stocks. The area’s coral reefs had been ravaged by pollution and overfishing, leaving “once complex marine habitats now reduced to rubble.” Artificial reefs can provide shelter for a limited species of fish and sea creatures in the short-term, but can they help us keep vibrant coral ecosystems alive long-term?

Bolstering fish stocks is a worthy project, but no artificial reef is a replacement for living coral, an animal that has evolved for millions of years to interact in equilibrium with its environment. Coral-reef ecosystems cover only a tiny sliver of planetary real estate, just 0.0025 percent of the world’s ocean floor, but they are home to fully 25 percent of all marine species—by some estimates, reefs beat even rain forests for biodiversity.

The value of this biodiversity to humans is staggering. By one estimate, coral reefs account for over $6.7 trillion of the annual global economy, more than four times the U.K.’s share. According to a 2014 report from the Food and Agriculture Organization, coral reefs are responsible for 17 percent of the protein we eat globally, and this number shoots up to as high as 70 percent in coastal or island countries like Fiji or the Maldives. Coral reefs also filter and clean polluted ocean water, and serve as protective barriers against increasingly violent storms. Perhaps most critically, coral-reef ecosystems provide half of the earth’s oxygen and absorb 30 percent of the carbon dioxide emitted from burning fossil fuels. Without reefs, this warming planet will get hotter, faster. We need coral, even if it needs us like the proverbial hole in the head. And yet, across the globe coral is dying at unprecedented rates.

Across the Caribbean and Florida Keys, two key coral species—staghorn and elkhorn—have declined by an astonishing 98 percent since the 1970s. Worldwide, coral has already declined by roughly 40 percent.  

Just last October, The National Oceanic and Aquatic Administration (NOAA), made the devastating announcement that with the return of El Niño, we are seeing the third worldwide coral bleaching event in recorded human history. “Bleaching” occurs when ocean temperatures stay too warm for too long—sometimes just a degree or two warmer than usual—and corals react to the stress by kicking out their symbiotic zooxanthellae, the tiny algae that live in their tissues, giving corals their vibrant colors and providing them with energy through photosynthesis. Without their colorful symbiotic partners, the coral turns an eerie, skeletal white. And without its main source of energy, it starts to starve. When coral bleaches, reef creatures flee or die in droves. In a matter of days, what was once a vibrant underwater ecosystem becomes a barren field of bone fingers reaching into an empty ocean.

Difference in average ocean temperature in January 2016 as compared to 1981-2010  (NOAA)

As I write this, a massive band of unusually warm water is spreading around the middle of the planet. Corals have already bleached across the Caribbean, Southeast Asia, and the Florida Keys. Just two weeks ago, coral started bleaching in Fiji. Thousands of blue and turquoise and pink reef fish washed up dead along the beaches of the Coral Coast. Victor Bonito, marine biologist and director of Reef Explorer Fiji, told New Zealand Radio that nearly a third of inshore corals have bleached and he has already witnessed “decades of damage.”

The first time a global coral bleaching event happened, when El Niño hit in 1997-98, 16 percent of the world’s coral was severely damaged. In the Maldives, it was as high as ninety percent. This time around, the bleaching is predicted to be even worse and is expected to stretch well into 2017. As Mark Eakin of NOAA put it in a statement released just a few days ago, “We are currently experiencing the longest global coral bleaching event ever observed.” Right now, the band of warm water is heading west from Fiji toward Australia’s Great Barrier Reef. Cooler weather could mitigate the damage, but already there are reports of up to 80 percent bleaching in sites along the northern edge of the World Heritage site. The Guardian reports that “authorities are praying for clouds and rain.”

There is no doubt that a profound shift is underway in today’s ocean, and coral reefs are the canaries in the coal mine of our carbon-obsessed planet. As a result of human activity, particularly the burning of fossil fuels, our ocean is not only warmer, on average, but also more acidic, because CO2 emitted from burning fossil fuels gets trapped in the ocean, and turns into acid. A landmark study published in Nature last month offers the first evidence that rising CO2 levels and acidification are severely stunting coral growth.

To say that the ocean we have known in our lifetimes is already gone is not doomsaying or pessimism. It’s a realistic assessment of where we stand, now. On Feb. 19, the UN World Meteorological Organization (WMO) announced that for the first time in recorded history the world passed the threshold of 1 degree Celsius above pre-industrial temperatures, halfway to the Paris treaty’s controversial 2 degree Celsius threshold, a point at which, once it becomes the average, a recent paper in Nature Geoscience reports all the world’s coral reefs will already be gone. Some estimates have us on track to speed past that 2 degree Celsius threshold in the next 20 years, but just a few days ago the planet briefly heated all the way up to the dreaded 2 degree Celsius, leaving climate scientists reeling.

Given the scope of devastation under way in our ocean, it’s hard to know whether new technologies like 3D printed reefs can make a difference. A bit like aquatic birdhouses, artificial reefs are often designed with a certain species in mind (red snapper in Bahrain), but they provide shelter for myriad species, including algae, anemones, octopus, and crab. If molded concrete units are the Soviet-era apartment blocks of the sea, the 3D printed unit off Bahrain is an aquatic Craftsman, the buff surface carefully grooved and pitted to attract free-floating baby coral polyps—the hope being that one day those artificial limbs might be carpeted in living coral. Similarly, a new system of 3D printed reef soon to be unveiled by Reef Design Labs, co-founded by Reef Arabia founder Dave Lennon, features interlocking units with a porcelain coating that boasts “dimples” and “a chemical makeup similar to coral” that may attract baby coral polyps.

While promising as a substrate for baby coral polyps, the materials these reefs are built of are guaranteed to last just sixty years. Most are not large or heavy enough to withstand being tossed around by a major weather event, and there is very little scientific data on what happens when you actually put them in the ocean. In a maddening catch-22, 3D printed reefs lack the imprimatur of data from scientific testing, which means it’s hard to secure funding to put them in the ocean, where data could be collected. So far, the unit off Bahrain is the only 3D printed reef in any ocean in the world, though plans are underway to sink six 3D printed reefs—designed to help corals recuperate from damage—off the coast of Monaco later this year. (Lennon is an advisor to the project.) Meanwhile, coral around the world is struggling to survive in warmer, more acidic waters.

For millions of years, corals have lived in changeable environments, pummeled by storms and the vicissitudes of climate, and they have evolved to be inherently dynamic and resilient systems. “Resilience” is a word overused to the point of nonsense in recent years, but the concept is meaningful in the context of coral-reef ecology. After the first bleaching event in 1998, 16 percent of the world’s coral in fifty countries bleached. Forty percent of that coral died, but that means 60 percent of it lived. “They can bounce back from disruption. They can bounce back from mortality,” says Gabriel Grimsditch, the senior project officer at the International Union for the Conservation of Nature, currently helping to develop coral-reef management plans.

Battered corals can recover from catastrophic events like bleaching or cyclones, but they need time. Corals grow slowly, averaging between .02 to 8 inches per year (a rate stunted by rising acidity), so even a fast recovery takes years. “You can’t stop a bleaching event,” says Grimsditch, “but you can manage for recovery. We can reduce local stressors like pollution and overfishing. We can design measures that might help give aquatic life a fighting chance.” Grimsditch is focused on managing reefs longterm. Less local pressure from overfishing, land-based pollution, and destructive coastal development means healthier coral before global events, which means greater resilience afterward and the possibility of healthier reefs in the future.

Of course, some species of coral will undoubtedly fare better than others, which will fundamentally alter the makeup of the world’s coral reef ecosystems. Recently, researchers have make the remarkable discovery that some genetically younger corals are able to live in hotter and more acidic waters than their forebears. There may already be corals that have adapted to live in our future ocean. “Let’s focus on the factors we can manage and help reefs be more resilient,” said Grimsditch. “If 3D printing helps, that’s great.”

This perspective—short-term pessimism, long-term optimism, a willingness to try—is increasingly prevalent among those concerned about the future of our ocean.  In Florida, marine biologist David Vaughn is using new aquaculture techniques to speed the growth and resettlement of centuries-old coral. Ruth Gates, a researcher at the Hawai’i Institute of Marine Biology, is breeding coral in an attempt to speed evolution of a new “super-coral” that can thrive in warmer and more acidic water. In Curaçao, marine biologist Kristen Marhaver is using 3D printed discs to study coral larvae, and has found the species she studies prefer to settle on discs that are pink or white—the color of a healthy coral reef. One could imagine a super-coral farmed to healthy adulthood on 3D printed reefs.

Artificial reefs may help some corals survive the global transition from fossil fuels, or they may be all that’s left, underwater birdhouses of concrete and porcelain built for species that have adapted to survive without coral—the dark green algae and the glittering handfuls of homeless fish searching for a place to hide. This future ocean may not be ideal, but it too, is worth fighting for.

The oldest marine organism on the planet is a deep-water black coral, Leiopathes, living off the coast of Hawaii and carbon-dated to 4,265 years old. Down where Leiopathes live, temperatures are less dependent on fluctuating weather patterns at the surface, so this coral might have better odds at surviving the epic changes underway. The future remains uncertain, but we know that change is inevitable (the calcerous part of the Alps, known as the Northern Limestone Alps, used to be coral reefs) and we know we can’t reverse the effects of climate change on our oceans. The real hope is that some corals survive long enough for human civilization to wean itself from a carbon-based economy. In the meantime, we can ventilate the coal mine until we no longer need coal, and we can breed heartier canaries. Letting go is not the same as giving up.

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