Marine biologists scramble to stop a deadly epidemic decimating coral reefs

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• Nick Schifrin:

  Coral reefs around the world are in growing danger, due in no small part to rising temperatures connected with climate change.

  But, in Florida and throughout the Caribbean, there is now a new mysterious epidemic killing once healthy corals. Scientists are diving deep to find some answers.

  And science correspondent Miles O'Brien recently joined them on their mission to revive the reefs.

• Miles O’Brien:

  I have been scuba diving in Florida and the Bahamas for 35 years, which makes me an eyewitness to a slow-motion disaster.

  Marine biologist Karen Neely is also saddened by what she sees.

• Karen Neely, Nova Southeastern University:

  I know what it's like to go somewhere where you have had old friends and they're not there anymore. That's what we're seeing on the reefs here. Over the last 20 years, there's just been the continued loss of coral.

• Miles O’Brien:

  It's a global problem brought on by pollution, overfishing and the climate crisis.

  The Intergovernmental Panel on Climate Change predicts up to 90 percent of tropical coral reefs will vanish as soon as 2030 unless drastic action is taken to limit greenhouse gases. Grim as that is, here in Florida, things are worse.

  Neely is on a mission to stop a deadly coral epidemic decimating reefs here and throughout the Caribbean. First identified near Miami in 2014, stony coral tissue loss disease spreads and kills like wildfire. It strikes more than 20 of the 60 or so species of coral that live here. Mortality rates range from 66 to 100 percent. The iconic Pillar coral is one of the most susceptible.

  Valerie Paul, Director, Smithsonian Marine Station at Fort Pierce: It's heartbreaking. It's just unbelievable.

• Miles O’Brien:

  Marine biologist Valerie Paul is head scientist at the Smithsonian Marine Station at Fort Pierce. She's helping lead the urgent hunt for answers.

• Valerie Paul:

  When we started, we didn't know anything. We just knew it was killing coral tissue, right? We know more than we did a few years ago, but we surely don't know enough.

• Miles O’Brien:

  Corals are complex, fragile, and poorly understood animals. They survive thanks to a mutually beneficial or symbiotic relationship with algae that live in coral tissue.

  In this marriage, the coral is the homemaker and the algae brings home the bacon, actually, nutrients derived from photosynthesis. Many of the vivid colors of coral are actually created by the algae. So, white patches are signs disease or death.

• Valerie Paul:

  So really, this whole piece is diseased at this stage. This is fairly advanced disease on this coral.

• Miles O’Brien:

  But no one know what is sort of pathogen is at work. It could be viral or bacterial or perhaps some combination. Here, they isolated a beneficial bacterium that fights offs the disease.

• Valerie Paul:

  We started just testing it in the laboratory first in various aquarium studies with pieces of diseased coral and saw that it would slow down the disease or stop it entirely. So this was like, wow, this is cool.

• Miles O’Brien:

  So they are treating healthy corals with probiotics applied beneath a weighted bag. It looks promising, but it's still early. Antibiotics are also working.

  Karen Neely is part of a small team of researchers applying amoxicillin paste to ailing corals.

• Karen Neely:

  We can come back in a month, and that coral has no sign of disease, it's not dying anymore. And, eventually, it starts re growing.

• Miles O’Brien:

  Her team from Nova Southeastern University and others have collectively saved nearly 15,000 corals. Still, the researchers are well aware they're only making a small dent in a massive problem.

• Karen Neely:

  We really have to be quite selective. We're figuring out, what can we save, what might be OK if we can't get to it, and what are we going to lose regardless, and trying to get the most bang for the buck?

  We can't just pretend this isn't happening and not do anything about it, or the prognosis takes a sharp turn for the worse.

• Miles O’Brien:

  At the Florida Aquarium Coral Conservation Center near Tampa, they are fighting this disease on land.

• Keri O’Neil, Florida Aquarium Coral Conservation Center:

  So, this is a tank of corals that are going out into the ocean in a couple of weeks.

• Miles O’Brien:

  Keri O'Neil is the senior coral scientist here.

  At first, she hoped to participate in a massive effort by a team of scientists to harvest healthy coral from the reefs to create an ark, a desperate move to avoid extinctions.

• Keri O’Neil:

  However, they don't stop growing. And if you're keeping them under happy conditions, then they're just going to keep growing and growing.

• Miles O’Brien:

  She wondered if she could make endangered Pillar corals happy enough to reproduce. Something like that had never been done before with Florida corals in aquariums.

• Keri O’Neil:

  So you have to get all the seasonal cues right, the change in temperature, the change in daylight, sunrise, sunset, the moon phase, all of these different cues have to be just right in order for that one event to occur around the full moon of August.

• Miles O’Brien:

  The spawning happened on their first try in August of 2019.

• Keri O’Neil:

  We were just cheering and yelling and calling everybody, like, come in. We need help.

  (LAUGHTER)

• Keri O’Neil:

  And it's happened like clockwork every year since then.

• Miles O’Brien:

  So what started as a gene bank five years ago is now a huge thriving coral breeding center.

  Keri O'Neil occasionally joins divers from the Florida Fish and Wildlife Conservation Commission as they cement their offspring onto ailing reefs. The team uses little bamboo teepees, so the young corals don't become fish hors d'oeuvre. So far, they are thriving, maybe because they're young and strong, or maybe the worst of the epidemic has passed.

  Eventually, O'Neil hopes they will find the genes that make coral resistant and selectively breed animals that are immune to stony coral tissue loss disease. But, remember, the disease is just one of many threats.

• Keri O’Neil:

  We cannot save coral reefs without stopping climate change and cleaning up our environment. That takes time. In the meantime, we need to ensure that we don't lose the diversity that we have now, so that we can build back the population. Our work here is buying us time.

• Miles O’Brien:

  When Karen Neely swims past healthy corals that she has treated, she feels the same way.

• Karen Neely:

  I definitely don't feel like it's a futile effort. And I do feel like we have to do something.

  If you like seafood, you like coral reefs. If you like vacationing in Florida, you like coral reefs. You might not know it, but it's super important that we have them, and it's pretty problematic when we lose them.

  I think, in my lifetime, we will either start to see the swing back towards more healthy reefs, or we will see reefs continue to decline into something almost unrecognizable.

• Miles O’Brien:

  Imagine that, a world without thriving coral reefs. Not a pretty thought. It's heartbreaking to watch it happening right before my eyes.

  For the "PBS NewsHour," I'm Miles O'Brien 30 feet beneath the surface at Looe Key, Florida.