Saturday, October 18, 2008

Rebound reef

A coral reef endures against the odds

International Herald Tribune
October 6, 2008

KENTING NATIONAL PARK, Taiwan: At this seaside resort on Taiwan's southern tip, annual typhoons blast sludge and sediment onto fragile, shallow-water coral reefs. Hotels and villages sprinkle the reefs with sewage. A nuclear power plant boils them with discharged reactor-cooling water. Snorkelers and scuba divers trample on the reefs, sometimes breaking off chunks of coral as souvenirs.

And in 2001 a huge cargo ship sank off Kenting, destroying the coral it landed on and spewing more than 1,000 tons of fuel oil down the coastline.

As if all that were not enough, rising sea temperatures have increased the frequency of "coral bleaching," which can be fatal if it lasts much more than two to three weeks.

Yet in an age when such environmental stresses are killing off coral reefs worldwide, Kenting's reefs are doing surprisingly well. One scientist here said Taiwan might even turn out to be a "Noah's Ark" for corals.

"This is the era of global temperature change and ocean warming is a big problem for coral reefs," said Fan Tung-yung, a coral expert at Taiwan's National Museum of Marine Biology and Aquarium, in a telephone interview. "But Kenting is a refuge."

A research paper by John Bruno and Elizabeth Selig, published last year in the scientific journal PLoS One, comparing reefs throughout the Pacific and Indian oceans found that average coral cover (the amount of sea floor covered by live coral) was about 22 percent, whereas Fan said coverage off Kenting was 40 percent. Last year, when a coral bleaching spell wiped out many other reefs in the Asia-Pacific region, Kenting's survived - and bounced back quickly.

The reefs' relative stamina has drawn interest from marine biologists worldwide. Now, American and Taiwan scientists hope to make Kenting part of a U.S.-led global "early warning system" for coral reef monitoring.

Such a system would help Taiwan's scientists and officials better protect their reefs. It would also allow scientists to gather data to explain why some reefs - like Kenting's - are so robust, while others are languishing.

"The reefs of Kenting are very impressive in terms of their overall coral cover and coral diversity," Peter Edmunds, a coral expert at California State University at Northridge who has inspected Taiwan's reefs, wrote in an e-mail. "They offer a unique and very important opportunity to understand the reasons why some reefs seem to be surviving better than others throughout the world."

Scientists already have several hypotheses. Kenting's reefs are fortunate to be replenished by a steady supply of what scientists call "recruits" - new coral, in this case brought north from waters near the Philippines. That means that even when some coral is destroyed, new coral rushes in to take its place.

More important, though, are the tide-driven currents that regularly push up deeper, colder water to the shallow waters off Taiwan's southern tip. This type of "upwelling," says Fan, is very rare.

Edmunds and Fan believe the Kenting reefs' tenacity is related to their natural exposure to sharp variations in seawater temperature (as much as 9 degrees Celsius, or 16 Fahrenheit, over a single day) caused by these tidal patterns.

"It's possible that such thermal stresses somehow provide the corals with the ability to resist subsequent stress," said Edmunds. Toughened by the daily battering of such temperature swings, Kenting's reefs may simply shrug off hotter ocean waters that are so damaging to other reefs.

Oddly, the nuclear power plant may have also helped toughen the reefs, says Fan. The coral reefs in the area have had 30 years to adapt to higher temperatures (2 to 4 degrees Celsius higher) close to the outflow of cooling water from Taiwan's Third Nuclear Power Plant on Nanwan Bay - which also happens to be the site of a popular recreational beach.

To be sure, Kenting's reefs are faring well only in comparison with others around the world.

Dai Chang-feng, a coral expert at National Taiwan University's Institute of Oceanography, said in an interview that three decades ago, Kenting's coral reef coverage was as high as 75 percent to 80 percent, almost twice what it is now.

Models predict that by 2050, "most of the coral species in Kenting will disappear," Dai said. Specifically, his models predict that fewer than 50 of Kenting's 300 species will survive by 2050, with few or none left alive by 2100.

To help them avoid that fate, scientists and government officials first need better data on what exactly kills off corals and why some like Kenting's are hardier.

Enter the U.S.-led Integrated Coral Observing Network. Scientists in Taiwan and officials of Kenting National Park (which has jurisdiction over the reefs) have been meeting with U.S. National Oceanic and Atmospheric Administration scientists to discuss Taiwan's inclusion in the network. Kenting could be incorporated next year, said Fan and others involved in the project.

The ambitious network aims to provide a global picture of the health of coral reefs, both for research purposes and as an "early warning system" when coral reefs are threatened. Already active in the Bahamas, it uses underwater sensors that gather water temperature and other data and beam it to satellites. That data is then linked to a network that allows for real-time monitoring of reefs worldwide.

"The purpose of the sensors is to study how global warming affects corals and to know what to watch for," said Keryea Soong, a coral expert at National Sun Yat-sen University's Institute of Marine Biology in the southern port city of Kaohsiung. "We can design experiments to better understand 'bleaching.' Satellites can give you a picture of a wider area, but with the sensors, we can know the temperatures on a much smaller scale, such as in Kenting."

Bleaching, one of the key threats to coral reefs, occurs when coral loses its symbiotic algae due to stresses such as high water temperatures. That removes reefs' coloration and their main source of nutrients.

When the monitoring network's sensors show a reef under threat, scientists and Kenting National Park officials will be able to take immediate steps - for example, temporarily banning water activities such as snorkeling or boating in the area.

"The whole world is worried about the health of coral reefs," said Shih Chin-fang, former director of Kenting National Park, in an interview. "So a group of experts is working very hard all over the world to link up this monitoring system to the Internet."

Ultimately, those are stopgap measures, which do not address the long-term threat to Earth's coral reefs posed by global warming. Edmunds worries that Kenting's reefs, while appearing tough, may just be "lagging" deteriorating reefs elsewhere - and that their decline is "just around the corner."

Said Edmunds: "I've seen similar effects in the Caribbean - one reef that was doing great for 20 years, while others around it were declining, in 2005 suddenly started to die off at an alarming rate."

For now, he and other scientists are hoping that Kenting's reefs really are exceptional. And soon they hope to know why.

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