As a tourist destination Koh Samui relies on having great weather for the tourists to enjoy. Four years ago for the first 3 months of the year the weather was unusually good, with temperatures reaching as high as 48 degrees, which was high enough for even the most hardcore sun worshippers.
What many people don’t know is that Corals are actually animals, related to anemones and jellyfish. Corals consist of a limestone structure filled with thousands of small animals called polyps. Each polyp has a skeleton cup, tentacles with stinging cells, a mouth and a stomach. The tiny tentacles snatch at passing plankton for food, but for their main course, reef-building corals have devised a much more ingenious method to get fed.
Algae called zooxanthellae live within each coral. In return for a safe sunny home, the zooxanthellae eat the nitrogen waste that the coral produces (nitrogen is very good for algal growth) and, like all plants, algae turn sunlight into sugars by the process of photosynthesis. The sugars produced by the zooxanthellae make up 98 per cent of the coral's food. So, without having to do any work at all, the coral is kept clean and well fed, and the zooxanthellae with their brilliant reds, oranges and browns give corals their colour.
Rising water temperatures blocks the process that converts carbon dioxide into sugar. This results in a build-up of products that poison the zooxanthellae. To save itself, the coral spits out the zooxanthellae and some of its own tissue, leaving the coral a bleached white. The bleached coral can recover, but only if cooler water temperatures return and the algae are able to grow again. Without the zooxanthellae, the coral slowly starves to death.
After about 3 months of heat a change for the worse in the weather and dropping of temperatures lead to the water temperature dropping to 29-30 degrees and started to have an immediate impact on the coral, with many starting to go back to their original brown colour within a couple of days. Some took a bit longer to get back to health and thankfully the temperatures dropped just in time to prevent permanant damage.