(AP) -- Scientists plan to monitor corals in the Northwestern Hawaiian Islands next month for signs of bleaching that could harm the reefs.
Corals become stressed and expel the algae that live inside them when temperatures are warmer than normal. This causes corals to lose their color and appear white.
Corals may die if this continues for extended periods, depriving fish of vital food and habitat.
Researchers will be observing coral in the Papahanaumokuakea Marine National Monument during September - the hottest month of the year in Hawaii, monument deputy superintendent Randall Kosaki said Friday.
They're due to leave for the remote atolls aboard the research ship Hiialakai in a week, he said.
Kosaki measured surface temperatures of 82 to 84 degrees during another research trip to the Northwestern Hawaiian Islands earlier this month. That was very warm, particularly for waters that far north, he said.
Kosaki also noted there's currently a mass of warm water from Southeast Asia that's pushing into the North Pacific.
"It's warm now. If it cools off we might not have a bleaching event. If it stays warm for an extended period we might have a bleaching event," he said.
Bleaching would be likely if temperatures stay higher than normal for more than two to four weeks, Kosaki said.
The Northwestern Hawaiian Islands, which are home to 69 percent of the coral under U.S. jurisdiction, had bleaching events in 2002 and 2004.
Warm waters in Southeast Asia have already harmed reefs this year in Indonesia, Malaysia, Thailand, Vietnam and Sri Lanka.
In May, marine biologists working for the Wildlife Conservation Society observed coral bleaching off Indonesia's Aceh province as surface waters in the Andaman Sea peaked at 93 degrees - 7 degrees higher than long-term averages.
Subsequent surveys found 80 percent of the bleached corals had died.
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