Climate change and rising ocean temperatures have been greatly affecting coral reefs around the world for the last three decades. In fact, 4 of the hottest years on record are within the last 15 years. Abnormally hot years are those 2-3 degrees hotter than normal, and can cause widespread coral bleaching, increased incidences of disease, and declines in biodiversity. Globally, corals are being lost of a rate of 2% per year, with 16% of the world’s hard corals dying just in 1998, due to coral bleaching.
2010 was also a particularly hot year, when again mass coral bleaching was observed throughout much of the earth’s reefs. On Koh Tao, shallow reefs dominated by branching corals were most affected, with up to 76% mortality in some areas. For many divers here on the island who had never experienced something like this, it seemed like the end of our local reefs. But, luckily our corals fared well in many of the most popular dive sites. As you can see in the graph above for some of the shallow sites (3-6 meters), the coverage of corals between 2009-2011 decreased quite dramatically. But by 2012 about half of that loss had been replaced.
Now, 2 years on, data we have been collecting is showing a strong rebound in coral coverage. This can be attributed to growth of the coral which survived the bleaching, and the settlement and growth of new coral larvae in the dead areas. We also have been working hard since the bleaching event to remove coral predators, install artificial reefs, and use coral nurseries to rehabilitate broken or damaged corals.
We are optimistic about the future of our local coral reefs, but it is a cautious optimism. No matter how many corals we can grow or save, all can be lost in a single summer when temperatures are too high. It takes all of us to protect our ocean, and it starts with the things you do every day. We welcome you to join our efforts, or start your own elsewhere. After all, it is Our Ocean, and Our Responsibility.
The data shown here was collected by our interns and students through the Koh Tao Ecological Monitoring Program (certified by both PADI and SSI). If you are interested in taking this course you can sign up from our courses page.