Scientists try to regrow a dying coral reef 25 times faster than nature

JUDY WOODRUFF: Finally tonight: new hope for how to restore dying coral reefs. It involves what could be a new and groundbreaking kind of undersea transplant.

Hari Sreenivasan has our story.

HARI SREENIVASAN: Half a mile off the Florida Keys, a small boat of scientists is confronting a vast underwater crisis.

Biologists David Vaughan, Christopher Page, and Rudiger Bieler are attempting lifesaving transplants for Florida's coral reefs, which are dying at alarming rates.

BILL CAUSEY, NOAA Office of National Marine Sanctuaries: This is America's only living barrier coral reef here in the Florida Keys, and it is in a perilous state at this point in time.

HARI SREENIVASAN: Billy Causey, the Southeast regional director of Marine sanctuaries for the National Oceanic and Atmospheric Administration, says the problem is even bigger than Florida. One-quarter of the world's corals have died in recent decades, a consequence of pollution, overfishing and climate change.

BILL CAUSEY: There's a global crisis right now occurring with coral reefs and their decline. Our corals are already at the very edge of their existence. Coral reefs provide the structure, the home and the food for all the reef fish that are important both commercially and recreationally.

HARI SREENIVASAN: Trying to reverse that decline, the scuba diving scientists are grafting new corals onto decimated reefs.

Dave Vaughan leads the transplant team at Mote Tropical Research Lab in Summerland Key, Florida.

What are we looking at here in all these tanks?

DAVID VAUGHAN, Director, Mote Tropical Research Laboratory: Well, these tanks are growing corals, which are part animal, part plant, part mineral. They're basically a little understood organism.

HARI SREENIVASAN: While other biologists have tried transplanting new corals to dead reefs in recent years, the Mote team's experiment is seen as groundbreaking. That's because the hard coral species grown in Dave Vaughan's tanks form the reef's critical structure that, until recently, took centuries to grow.

DAVID VAUGHAN: Most of these corals, the size of a good boulder, the size of a small car, would be 500 to 1,000 years old. But now, since we have lost 25 to 40 percent of the world's corals, we can't wait 100 years.

HARI SREENIVASAN: In fact, Vaughan and his team aren't waiting. They discovered that, when cut into small strips, the slow-growing living corals quickly try to heal themselves.

Biologist Christopher Page compares it to human skin, which will heal quickly after an injury.

CHRISTOPHER PAGE, Biologist: By cutting it, you're actually stimulating it to grow.

HARI SREENIVASAN: Now these reef-building corals will grow at a rate 25 times faster.

How long do these tiny ones that look like little mini-cupcakes, how much — how long do those take?

DAVID VAUGHAN: We can grow that size in about four months. In four months, we can get what would have taken two years.

HARI SREENIVASAN: And then what about these? These are bigger now?

DAVID VAUGHAN: This is a brain coral.


DAVID VAUGHAN: And this would have taken 10 to 15 years to grow.

HARI SREENIVASAN: And it took how long in the lab?

DAVID VAUGHAN: About one year. Now we're trying some plants where we take about 20 of these. We put them all in a circle about the size of a dinner plate. And we think that, in one year, it will grow a coral this big, which would have taken 25 to 50 years in the wild.

BILL CAUSEY: What he's getting with this microfragmentation is growth spurts unlike anything we have ever seen.

HARI SREENIVASAN: Once the corals are successfully grown in the nursery, the team searches for a transplant match, dead corals of the same species.

RUDIGER BIELER, The Field Museum of Natural History: A big coral boulder, it is essentially just a rock. It's the material that the living tissues have deposited over dozens or a hundred years, but the only thing that's alive is that little veneer of tissue on the outside, which is essentially what we are bring back.

HARI SREENIVASAN: But before the transplant, the corals are left in a cage for 30 days.

DAVID VAUGHAN: There are so little new corals out there that if we put these bright little nuggets out there, things like parrot fish and other predators haven't seen that in such a long time, they say, boy, that looks like a chocolate-covered strawberry.

HARI SREENIVASAN: When the corals lose some of their color and attraction to fish, Vaughan and Bieler punch holes in the dead structures and epoxy the new corals, hoping they will eventually fuse together.

Rudiger Bieler likens the process to human hair plugs. Bieler is a curator from the Field Museum of Natural History in Chicago, one of the partners in the project. And he is documenting the marine life the project may attract.

RUDIGER BIELER: To see what lives in that area before we do the restoration, what happens during the restoration, and what kind of species are coming in afterwards.

HARI SREENIVASAN: But the question remains, will these new corals, subject to same ocean stressors as their predecessors, survive in the wild? For that, the team is recreating current ocean conditions.

DAVID VAUGHAN: We change the pH in each tank and we look to see which ones are going to tolerate those conditions.

HARI SREENIVASAN: So, essentially predicting, kind of creating the future environment here for you?

DAVID VAUGHAN: That's right, seeing which ones will be the winners and which ones will be the losers, so we're always using the winners.

HARI SREENIVASAN: So you basically are assuming that ocean acidification continues at this rate, this is what the ocean will be like, so if you can figure out which ones survive, put those in the ocean?

DAVID VAUGHAN: Absolutely. You are right on target. That's exactly what we're doing.

HARI SREENIVASAN: While it may not be the solution to saving the world's coral reefs, NOAA Director Bill Causey says it is buying time.

BILL CAUSEY: And giving us time for our reefs to hang on as long as they can just by having stock that we can eventually put back out there, but it's going to take our global leaders to address climate change. And we have to have the time for those actions to take place.

HARI SREENIVASAN: In the Florida Keys, I'm Hari Sreenivasan for the PBS NewsHour.