JAKARTA, Indonesia — Coral that survived the 2004 tsunami is now dying at one of the fastest rates ever recorded because of a dramatic rise in water temperatures off northwestern Indonesia, conservationists said, warning Wednesday that the threat extends to other reefs across Asia.
The Wildlife Conservation Society deployed marine biologists to Aceh province, on the tip of Sumatra island, in May when surface waters in the Andaman Sea peaked at 93 degrees Fahrenheit (34 degrees Celsius) – a 7 degree Fahrenheit (4 degree Celsius) rise over long-term averages.
The teams discovered massive bleaching, which occurs when algae living inside coral tissues are expelled. Subsequent surveys carried out together with Australia's James Cook University and Indonesia's Syiah Kuala University showed 80 percent of those corals have since died.
Though the scientists have yet to submit the data for publication in a peer-reviewed journal, they and others say the speed and extent of mortality appears to exceed that of other bleachings in recent history. The cause appears to be the warming seas, which to some degree can be blamed on global warming.
"This is a tragedy not only for some of the world's most biodiverse coral reefs, but also for people in the region," said Caleb McClennen, the New York-based group's marine program manager for Indonesia, noting that many depend on the rich marine life for their food and money earned through tourism.
Coral formations were severely damaged by El Nino-linked warming in 1997 and 1998.
They were just bouncing back when a Dec. 26, 2004, earthquake off Sumatra triggered a tsunami that killed more than 230,000 people in a dozen countries. The disaster damaged more than a third of Aceh's reefs, but scientists said they recovered faster than expected, thanks largely to natural colonization and a drop in illegal fishing.
"It's a disappointing development, particularly in light of the fact that these same corals proved resilient to other disruptions to this ecosystem," Stuart Campbell of the Wildlife Conservation Society wrote on their website.
"It is an unfortunate reminder that international efforts to curb the causes and effects of climate change must be made if these sensitive ecosystems and the vulnerable human communities ... that depend on them are to adapt and endure," Campbell wrote.
The high water temperatures – which the National Oceanic and Atmospheric Administration's Coral Hotspots website indicates have affected the entire Andaman Sea and beyond – also occurred soon after the sun was at its zenith and at time of little cloud cover or wind.
Clive Wilkinson, a coordinator at the Global Coral Reef Monitoring Network in Australia, called it a "lethal combination" for coral, especially when it continues for more than a month, as was also the case in 1998.
The hotspot has affected reefs across Indonesia as well as in Malaysia, Thailand, Vietnam and Sri Lanka, and it is now pushing its way northward.
"We are in a major heating period, it's breaking all records, and there are very furious worries now about the Philippines and eventually Taiwan and probably southern Japan," Wilkinson said. "This is really quite serious."