Scientists Warn of Coral Bleaching in Caribbean
ROBERT SIEGEL, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.
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And I'm Michele Norris.
Scientists say the largest ever event of coral bleaching in this hemisphere took place last summer. Bleaching happens when water temperatures rise. The reefs turn white, and they can die. Up to 70 percent of corals were affected in some parts of the Caribbean, from Florida in the north to Panama in the south.
NPR's Lourdes Garcia-Navarro traveled to a string of islands off Panama called Bocas del Toro, to see how some of the affected reefs.
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Dr. RACHEL COLLIN (Director, Bocas Branch, Smithsonian Tropical Research Institute, Panama): We're right next to a small patch reef around a couple of hundred meters in diameter.
LOURDES GARCIA-NAVARRO reporting:
Dr. Rachel Collin is the director of the Bocas Branch of the Smithsonian Tropical Research Institute in Panama. As the boat drops anchor in this bay in the area of Bocas del Toro on Panama's Caribbean coast, she says that when her scientists first noticed the bleaching here, they could see that the reef had been hurt--badly.
Dr. COLLIN: We could tell in Bocas, definitely, that it was a severe event. And when I was here in August, so a couple of months after the main bleaching event, most of the corals had bleached, especially the big brain corals. But there's also, on the far side, a big patch of soft corals, the Gorgonian, but the soft corals also were bleached, so you could see the sort of tall, flexible, finger-like colonies. And they're usually are brown-colored, too, like the corals and they were white as well. So these big white ghostly fingers waving, waving in the, in the current.
GARCIA-NAVARRO: Now, months later, she's come back to see how the reefs are doing.
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GARCIA-NAVARRO: With her snorkel gear, she jumps into the water, and after paddling around, her worst fears are confirmed.
Dr. COLLIN: The shallowest part of the reef here, which is less than probably two feet of water most of the time, is almost completely dead. It's just a, you can see the skeletons.
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GARCIA-NAVARRO: A 20-minute boat ride away over the green waters that feed red mangroves is another reef.
Dr. COLLIN: We're on a reef that we call Broldan(ph), and this is where one of our long-term temperature sensors is. And what we can say is this year, in June, the average water temperature was 1.8 degrees warmer than it normally is.
GARCIA-NAVARRO: Over the summer, this was one of the hardest-hit reefs.
Dr. COLLIN: Corals can be very sensitive to the water temperature. It's one of the key factors that causes coral bleaching. And this kind of long-term temperature stress is really hard on the corals. And a difference of one or two degrees can make a huge difference.
GARCIA-NAVARRO: But as she swims around, a surprise.
Dr. COLLIN: The corals actually look pretty good right here.
GARCIA-NAVARRO: Technically, coral bleaching happens when the symbiotic zooxanthellae, a tiny algae, is expelled because of high water temperatures. Losing the algae not only strips the coral of color, but can lead to the death of the reef. But they can recover as Dr. Collins saw. This has led to a debate in the world of coral scientists.
Dr. Mark Eakin is an oceanographer with the National Oceanic and Atmospheric Administration's Coral Reef Watch. For him and other scientists, coral bleaching is a sign of the catastrophic changes that are afoot, due to global warming.
Dr. MARK EAKIN (Oceanographer, National Oceanic and Atmospheric Administration Coral Reef Watch): The corals are the basis of the ecosystem in the Caribbean, just like the trees in the rainforests that serve as the habitat for all the birds and mammals and other life in the forest. The corals serve as the basis for the food chain, the basis for the ecosystem, the habitat in which everything lives.
GARCIA-NAVARRO: And Eakin says that while some of the corals are recovering, preliminary data shows that there has been a 20 percent mortality rate in some of the coral colonies. That's extremely high. It takes decades for some types of coral to grow, in some cases, up to 50 or 100 years.
Dr. EAKIN: In the Caribbean, unfortunately, we don't have the potential for recovery, or we don't have the tendency for recovery that we have in the Pacific Ocean. There's not as much recruitment of new corals that comes in by sexual recruitment, basically like having seeds come into an area. That's not as common in the Caribbean.
GARCIA-NAVARRO: The Pacific Basin was hit by a large bleaching event in the late 1990s, but much of the reefs recovered. Which leads to the other side of this debate. No one says bleaching is a good thing, but some scientists do believe it may not be catastrophic.
The head scientist on corals at the Smithsonian Tropical Research Institute in Panama is Hector Guzman.
Dr. HECTOR GUZMAN (Chief Scientist, Smithsonian Tropical Research Institute): Sure, they are adapting to this kind of thermal stress in a way, slowly going into it. And we have evidence for the Pacific side. So I expect that in the long term, for the Caribbean reef, of course, some species might not survive, but most of them might start adapting to these kind of thermal changes.
GARCIA-NAVARRO: Dr. Guzman says that surviving corals may become more resilient to the changes brought about by rising temperatures by picking up more bleaching-resistant zooxanthellae. But that's still just a theory.
Dr. David Kline is doing his post-doctorate with the Smithsonian. He's a coral reef ecologist who specializes in coral disease. He says that while scientists are still trying to figure out what these repeated and increasing bleaching events will mean for the survival of coral reefs, there are many other perils for these beautiful and fragile systems.
Dr. DAVID KLINE (Coral Reef Ecologist, Smithsonian): I think there's so many stresses on reefs these days that I'm sad and I'm a little scared of what the future of reefs are, especially Caribbean coral reefs 'cause Caribbean reefs are the most stressed.
Just in the eight years I've been working on corals and studying corals, I've seen whole reefs disappear due to a combination of events.
GARCIA-NAVARRO: Dr. Kline says disease caused by pollution and overexploitation has also been decimating coral colonies. And that makes them more susceptible to bleaching.
Dr. KLINE: There are countless reasons why we should care about coral reefs. They prevent erosion and runoff from the land, they prevent landmasses from hurricanes and storm damage. The tsunami damage, there are several studies going on that have pretty convincing evidence that areas that had healthy and intact reefs suffered much less damage than places where they had lost the reefs. They also are a major nursery for many commercially important species, including fish and shellfish, lobsters. So many of the species that we eat from the ocean have at least one phase of their lifecycle on coral reefs.
GARCIA-NAVARRO: He says he hopes that reefs will not die out in 50 years as some predict. But he says the future is uncertain.
Lourdes Garcia-Navarro, NPR News.
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