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.
On the 26-day voyage, divers noticed moderate to high bleaching in about 27 percent of shallow reefs around Kure Atoll and 19 percent of the reef area around Pearl & Hermes Atoll, scientists 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.
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.
Federal scientist Rusty Brainard said 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.