SINGAPORE A dramatic spike in ocean temperatures off Indonesia's Aceh province has killed large areas of coral and scientists fear the event could be much larger than first thought and one of the worst in the region's history.
The coral bleaching -- whitening due to heat driving out the algae living within the coral tissues -- was first reported in May after a surge in temperatures across the Andaman Sea from the northern tip of Sumatra island to Thailand and Myanmar.
An international team of scientists studying the bleaching event found that 80 percent of some species have died since the initial assessment in May.
More coral colonies were expected to die within the next few months and that could spell disaster for local communities reliant on the reefs for food and money from tourism.
"I would predict that what we're seeing in Aceh, which is extraordinary, that similar mortality rates are occurring right the way through the Andaman Sea," said Andrew Baird of James Cook University in Townsville, in the Australian state of Queensland.
If so, that would make it the worst bleaching recorded in the region, said Baird.
Scientists from the Wildlife Conservation Society and Syiah Kuala University in Aceh have also been assessing the damage.
"This one of the most rapid and severe coral mortality events ever recorded," the U.S.-based WCS said in a statement.
It also fits a pattern of climate extremes, from heatwaves to flooding, that have hit many areas of the globe this year.
Between April and late May, sea surface temperatures in the Andaman Sea rose to 34 degrees Celsius or about 4 degrees C above the long-term average, according to the U.S. National Oceanic and Atmospheric Administration's Coral Hotspots website. (See: here )
"Similar mass bleaching events in 2010 have now been recorded in Sri Lanka, Thailand, Malaysia and many parts of Indonesia," the WCS statement said.
Baird, of James Cook University's ARC Center of Excellence for Coral Reef Studies, told Reuters that climate change could have played a role in the extreme ocean temperatures around Aceh.
"There might be one of these cyclic climate phenomena driving it but it's much more severe than you would predict unless there was something else forcing it, which is almost certainly global warming," he told Reuters on Tuesday.
The bleaching is a blow to local communities in Aceh still recovering from the 2004 tsunami. That disaster caused relatively little damage to reefs and Baird said some areas had showed a dramatic recovery.
Baird said reefs in Indonesia would normally take 5 to 10 years to recover from localized bleaching. But if the event was spread across a much wider area, recovery would take longer.
"I suspect the scale of this event is so large there is unlikely to be many healthy reefs in the rest of Aceh."
(Editing by Nick Macfie)