June 2010 – Coral Bleaching Report for Koh Tao

Download our Coral Bleaching Report June 2010 HERE (pdf format)
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There’s a lot of talk around the island recently about the widespread bleaching experienced on all of our reefs. Many people who have not dived for a couple of weeks (or months) are most surprised to see the rapid change in appearance of many of the corals.

Many questions have been posed regarding the mechanisms of bleaching and why neighbouring colonies will react differently under the stress of warmer seas. Many people have been wondering if all the corals are dead or whether they will recover to their former glory. I hope to answer a few of these questions here. I also plan to elaborate on what we can expect in the months to come.

Current Bleaching Conditions
With the 2009-2010 El Niño, the Indian Ocean has been experiencing significant coral bleaching thermal stress since the beginning of this year  in a spatial pattern similar to that seen in 1998. Most of the northern Indian Ocean and Southeast Asia regions have been experiencing intensive thermal stress. Significant bleaching has been reported in Maldives, both sides of the Thailand Peninsula (Andaman Sea and Gulf of Thailand), Cambodia, Indonesia, and the Anilao region of the Philippines.

“The thermal stress has persisted and even increased in the other areas in the northern Indian Ocean and Southeast Asia. The rainy season has just started and is expected to relieve the high thermal stress in these regions and promote the recovery of bleached corals.” The ‘rainy season’ is relevant for the west coast but for us on Koh Tao we usually experience some carry over effects during June –August including increased winds and rain. Both of which will be beneficial for the reefs of Koh Tao.

Koh Tao has managed relatively well so far. Many species of coral have suffered severe bleaching. Some mortality has already been experienced but not on a widespread scale yet. Many species that were the first to bleach in April-May are still managing to withstand the onslaught. There have also been some examples of recovery. These admittedly have been few. But there are many positive signs.

We are still at a very crucial time with hot, calm conditions still prevailing for the most part. The next 2 – 4 weeks will be critical in determining whether many of Koh Tao’s coral survive.

Recovery will take months and maybe years, so don’t expect the rapid return to colour akin to the speed with the loss of colour over the past two months. It is a lot easier to ‘break’ something than to put it back together.