Magazine article National Parks

Hot on the Trail

Magazine article National Parks

Hot on the Trail

Article excerpt

So-called supercorals in the National Park of American Samoa may hold clues to saving coral reefs everywhere.

PETER CRAIG WAS CURIOUS. The recently retired chief biologist for the National Park of American Samoa for 20 years, Craig was on the island of Ofu, about 60 miles east of the main island (in the neighborhood of Fiji), when he came across a lagoon with a number of shallow pools, arrayed, he says, "like a string of pearls." The pools were of varying depths, and supported almost 100 species of vibrant corals. And during the low afternoon tides in the summer, when the pools were cut off from the sea, they got really, really hot.

Corals, Craig knew, are not supposed to thrive in hot water. He wanted to see what, exactly, these corals were enduring, so he dunked thermometers in some of the pools. He found that the temperatures fluctuated by as much as il0 F during a single day. Sometimes, the water was well over 90o F. Craig was astounded. Corals elsewhere died when water temperatures rose by less than 2° F. Yet these corals seemed at home in swings more than five times that.

He suspected he had stumbled onto something big. To lure an academic scientist to investigate even more, he published his observations in the journal Coral Reefi in 2001 and more generally spread the word that Ofu was worth a look. "We certainly played up the romantic pictures of the South Pacific," he says. "We played that card pretty shamelessly, actually."

As hosts to some of the richest biodiversity in the ocean, corals are usually not a hard sell. More than half a billion people live near corals, relying on them for food, shelter from storm surges, and the income that tourism brings. And while a coral may look like a single entity, it's actually a partnership between two microscopic organisms: a polyp, which is a tiny assemblage of mouths and tentacles; and a single-celled organism, usually an alga or dinoflagellate, which lives within that assemblage. The former builds a tiny calcium-carbonate structure that shelters the latter, and, through photosynthesis, the latter provides food to the former. Millions of these little partnerships accrete to form enormous, iconic reefs.

Globally, though, coral reefs are in trouble, and the reefs in American Samoa are no exception. Some suffer from heavy fishing pressures, while others are sullied by pollution. More broadly, there is the looming specter of climate change, which is predicted to increase sea temperatures. Rising temperatures can cause corals to expel their algal partners. The corals turn bone white and die - a phenomenon called "bleaching." The national park, as Craig well knew, had endured major bleaching events in 1994, and would again in 2002.

Fortunately, Craig's paper caught the attention of Stephen Palumbi, a biologist at Stanford University. Palumbi first visited Ofu in 2004 and has studied corals there ever since. Through a series of experiments, he and his students have shown that the Ofu corals are uniquely equipped to handle high water temperatures. In one recent study, published in Coral Reefs in 2011, Palumbi and Tom Oliver, a postdoctoral researcher, examined how corals from shallow pools on Ofu would fare in conditions predicted under climate change, compared with corals from nearby deeper pools that weren't thought to be as robust. …

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