Thailand is closing 18 dive sites to give its coral a chance to recover.

The dive sites closed include East of Eden in the Similans; Ao Pakkad, Ao Suthep, Ao Mai Ngam, Koh Stork and Hin Kong in the Surin Islands and Hin Klang near Koh Phi Phi. Over 80% of the coral at each site had been damaged, National Parks, Wildlife and Plant Conservation Department chief Sunan Arunnoparat said.

Sea temperatures have risen 2 to 4 degrees Celsius in some places, causing the coral to “bleach”. Bleaching occurs when warmer than tolerable temperatures force corals to cast out the tiny algae that help the coral thrive and give them their colour. Without these algae, the corals turn white and, if the condition persists for too long, eventually die. Branching corals such as table and staghorn coral are especially susceptible to coral bleaching.

The bleaching is said to be the worst in 20 years.

Sunan Arunnoparat said he could not say how long the dive sites would be closed but diving activities probably would be banned until the end of the monsoon season in October.

Mr Sunan added that curbs would be imposed on tourist visits to some sites, and public awareness of marine life conservation would be promoted in other measures to deter bleaching. Although as the bleaching has been caused by increased water temperatures, it is hard to see how alerting people to marine life conservation will help in the short term. “A task force will monitor the situation and issue measures to speed up coral rehabilitation”, he said.

There has been a mixed response from diving companies. Dive operators in Khao Lak support the closure. The Khao Lak Dive Operators Forum, which represents 26 dive shops, issued this statement

“In the Similan and Surin Islands, the highest impact has been on hard corals in shallow water, where the sea temperature is generally higher than in deeper water. Members of the KLDOF have been very happy to observe a speedy recovery of certain types of coral, especially soft corals, which appeared to have suffered from the bleaching effect as well. Corals located deeper than 12 meters have suffered no or very little damage.

We as dive operators are passionate about the environment in which we live and work. Therefore we are very concerned about the condition of the reef. It is proven that there is absolutely no connection between diving and coral bleaching, but we feel the need to be even more careful around the reef to prevent further stress.”

Indeed they go further and recommend that more dive sites should be closed, namely Beacon Reef and Breakfast Bend in the Similans.

Studies show that coral return to health after bleaching within two to three years when the surrounding waters and reef are relatively healthy. Corals in stressful areas, affected pollution and overfishing for example, take much longer to recover.

Further reading:
Coral Bleaching Alarm for 2010, NOAA