Scientists see coral bleaching in the Northwestern Islands

Areas of bleached coral caused by warmer ocean temperatures were seen on the latest scientific voyage by federal scientists to the Northwestern Hawaiian Islands.

But scientists aboard a ship returning yesterday from waters in the Papahanaumokuakea Marine National Monument said although bleaching seems to be occurring more frequently, they haven't noticed any mass bleaching so far this year in the region.

September is usually the warmest month of the year, so a mass coral bleaching seems less likely this year, scientists said.

"We've dodged the bullet," said Peter Vroom, chief scientist on the voyage for the National Oceanic and Atmospheric Administration.

Thirty percent of the Kure atoll reef and one-fifth of the Pearl and Hermes atoll reef bleached, according to scientists who spent the past month on a research cruise in the Papahanaumokuakea Marine National Monument. Corals at other atolls inside the monument were unaffected.

"There were certain areas where the bleaching was kind of severe, where it was just a white carpet essentially," said Peter Vroom, chief scientist of the cruise, which returned to Oahu on Wednesday.

"Other areas you would see a coral head that's had a lot of color, but maybe a quarter of it would be white," Vroom said.

Mass coral bleaching occurs when unusually warm water prompts coral to expel algae, robbing the coral of needed oxygen and nutrients and eventually causing the reef to die. Corals may recover if the algae returns, but they're still significantly weaker and more vulnerable to disease.

Papahanaumokuakea chief scientist Randy Kosaki said one factor that appears to have reduced ocean temperatures and potential bleaching was the recent storm from the northwest that blew and stirred Hawaiian waters.

Overall, scientists say it's unclear what the long-term effect of this summer's bleaching will be. Corals in the monument - which account for 69 percent of all coral under U.S. jurisdiction - were exposed to only two weeks of slightly above normal temperatures.

Rusty Brainard (left), chief of the NOAA Pacific Islands Fisheries Science Center's coral reef ecosystem division, said coral starts dying after about two months of being exposed to higher-than-normal temperatures.

Brainard added that scientists were surprised when they found coral bleaching in some waters in the Northwestern Hawaiian Islands in 2002 and 2004.

But he said coral bleaching has become more frequent in recent years.

"The fact that now we're seeing it as a common event is one of those early indications the ecosystems themselves are changing," he said. "The Northwestern Hawaiian Islands are in this transition to some new state."

Scientists said the pristine waters in Papahanaumokuakea provide good conditions for researching the effects of global warming without human factors, such as pollution and tourism, intruding into a study.

"This is giving us a special opportunity to understand ... what are the impacts of climate change on reefs ... and what can we do to help coral reefs survive," said Heidi Schuttenberg, research coordinator for Papahanaumokuakea.

Schuttenberg said that earlier this year she visited Thailand, where mass bleaching has turned coral reefs white down to 60 feet. (Left: coral bleaching in Australia)

Schuttenberg predicted the bleached corals would be sick by the time scientists return for another research trip next year.

"When corals are bleaching, they're essentially starving," Schuttenberg said. "They're very weak so even if they survive their event, they're much more vulnerable to disease, and they have much lower reproductive capacity."

PAPAHANAUMOKUAKEA a World Heritage Site

Papahanaumokuakea consists of remote, mostly uninhabited atolls northwest of the main Hawaiian Islands and the waters surrounding them. The monument is the nation's single largest conservation area and is nearly 100 times larger than Yosemite National Park. President George W. Bush made the area a national monument in 2006.

It's home to 69% of the coral reefs in U.S. territory. It also hosts 7,000 marine species, a quarter of which are found only in Hawaii. The area is off-limits to fishing, allowing for healthy and abundant populations of sharks, ulua or jackfish, and other marine life.

Recently this year the Papahanaumokuakea Marine National Monument — a pristine haven for coral and other marine life, and a treasured site of ancient Hawaiian shrines — has been named a U.N. World Heritage site.

The area northwest of the main Hawaiian islands is the only U.S. location to make the list for both natural and cultural reasons, said monument spokesman Dan Dennison.

Haunani Apoliona, chairwoman of the Office of Hawaiian Affairs, said the listing will help preserve Papahanaumokuakea for future generations.

"We are very proud of this historic inscription," Apoliona said in a statement.

Source:
Star Advertiser, "Scientists see coral bleaching in the Northwestern Islands", accessed October 1, 2010
Kansas City.com, "Remote Hawaii atoll corals suffer some bleaching", accessed October 1, 2010
The News Chronicle,"Papahanaumokuakea Marine National Monument declared a World Heritage Site", accessed October 1, 2010