Study in Australia Finds Ocean's 'Thermostat' Helps Protect Reefs in Deep Water

By The Associated Press

BANGKOK, Thailand: Some coral reefs may be protected from global warming by a natural thermostat that regulates sea-surface temperatures in the open ocean, researchers said Wednesday. The research team led by reef specialist Joan Kleypas studied a region of ocean northeast of Australia where surface temperatures have risen little since 1980.

Reefs there suffered fewer episodes of bleaching, when corals expel the colorful, microscopic algae that provide them with nutrition. Bleaching episodes, triggered by warming water, can be deadly for the coral and have damaged up to 40 percent of reefs worldwide. "Global warming is damaging many corals, but it appears to be bypassing certain reefs that support some of the greatest diversity of life on the planet," said Kleypas, who works at Australia's National Center for Atmospheric Research.

"In essence, reefs that are already in hot water may be more protected from warming than reefs that are not. This is some rare hopeful news for these important ecosystems." Kleypas said the study, which appeared last week in the journal Geophysical Research Letters, lent support to a much-debated theory that a natural ocean thermostat prevents sea-surface temperatures from exceeding about 31 degrees Celsius (88 degrees Fahrenheit) in open oceans.

The theory says that as surface waters warm, more water evaporates, which can increase cloud cover and winds that cool the surface. The theory has been debated for decades and gained support after evidence was found in fossil records that showed sea surface temperatures remained stable even when carbon dioxide levels rose significantly.

Terry Hughes, an Australian reef specialist at James Cook University who was not involved in the research, called the study "novel" and said it shows some parts of the ocean could serve as a refuge for reefs as oceans warm.

"An exciting inference is that warm-adapted strains of corals are less likely to bleach," Hughes said in an e-mail interview. Larvae from corals in tropical areas "could potentially migrate to cooler areas that are warming rapidly," he said. He said similar migrations occurred during rapid warming periods in the past.

Kleypas cautioned that many questions remain unanswered about the thermostat theory, including what the temperature limit might be, how extensive it is, what controls it and how climate change will affect it in the future. But she said the findings could help scientists decide where to concentrate their conservation efforts.

"Even if we have all these other stresses like acidification and pollution from human activities, it's wise to start trying to look for reefs which will be the least vulnerable to climate change," she said. "If we can prevent these acute effects from bleaching, we can buy some time while we figure what to do about climate change." Coral reefs face a myriad of threats, including overfishing, coastal development, pollution and changes to ocean chemistry caused by rising levels of carbon dioxide in the atmosphere.

But Kleypas said global warming is among the most dire since it causes ocean temperatures to rise, leading to coral bleaching. Unless the ocean quickly cools, allowing algae to grow again, bleached corals often collapse and die. Up to 40 percent of reefs have been hit by bleaching since 1980, she said.

To be continue in other article...

(Jakarta, Kamis 21 February 2008, 07.39 pagi)

Re-publish by Jacob Paradox from link (www.routers.com),(www.iht.com), (www.routers.com), (www.nytimes.com)