Bleaching and resilience: can reefs survive?

Yahoo News via AFP: Red anthia fish and rainbow-coloured wrasse dart among the glittering reefs of Indonesia's Wakatobi archipelago, as eagle rays and barracudas cruise past in the blue depths. It's hard to believe Wakatobi is anything but a thriving marine paradise, packing a bewildering abundance of life that supports 100,000 people and contributes millions of dollars to Indonesia's economy. But scientists are worried.

Last year, coral bleaching caused by higher sea temperatures wreaked havoc across the Coral Triangle, a region of rich tropical reefs spanning much of Southeast Asia and almost all of Indonesia. Up to 70 percent of the coral in Wakatobi, off the southeastern tip of Sulawesi island, was totally or partially bleached. In Aceh province, off the northern tip of Sumatra, as much as 90 percent was killed, scientists said.

Experts from environmental groups The Nature Conservancy and WWF, as well as the Indonesian government, returned to Wakatobi last month to see if the marine park's reefs had bounced back. Over two weeks of diving at sites with names like Table Coral City and Blue Hole, the team looked for signs of long-term damage or resilience, in the hope of learning more about how reef systems respond to climate-related stresses.

"In Aceh about 90 percent of the coral bleached, and that included some of the really big varieties that are hundreds of years old and had survived the (2004) tsunami but died because of the bleaching," said Joanne Wilson, deputy director for science in TNC's Indonesia Marine Programme.

"Very fortunately in Wakatobi ... it seems that only about five to 10 percent of the corals actually died. We're very lucky here." Bleaching occurs when corals respond to stress, such as stronger than normal direct sunlight or elevated sea temperatures, by expelling the algae that live inside them and give them their brilliant colours…

Coral in the Wakatobi archipelago, Indonesia, shot by Craig D, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license