Coral Bleaching

Coral bleaching in Thailand isn’t a new phenomenon but this year we’re seeing some of the most severe coral bleaching around Phuket for more than 20 years. For dive industry workers in Phuket it’s horrifying to see such a drastic change in the corals in such a short space of time. Since mid April the water temperature around Phuket has been fluctuating between 31 and 33 Celsius. On a daily basis divers notice more and more coral bleaching. The water is just far too warm.

Coral bleaching is the whitening of corals due to stress induced expulsion or death of algae like protozoa (zooxanthellae), which inhabit the structures. It’s these algae, which carry the pigment that gives corals its vibrant colors. Corals that form the massive reef ecosystems depend on these algae for their survival.

This video was taken on 11^th May 2010 at Home Run Reef, Racha Yai.

Once bleaching begins it usually continues even if the stress is removed. If the coral manages to survive the rise in water temperature, zooxanthellae will often require months to recolonize the coral and return to normal density. The new residents may be of a different species and possibly more resilient against further stresses. The worst case scenario is that the corals will die and never be recolonized. This could leave reefs barren of both corals and marine life.