Tien Og bay is an ecologically important area supporting a wide variety of fish life, and the largest known schools of Black Tip Reef Sharks around Koh Tao. The area is also economically important and popular for snorkeling and other marine based tourism activities. Although historically abundant and diverse, the area has been subjected to large natural disturbance events and chronic anthropogenic stresses. Currently it is one of the more degraded reef areas surveyed around Koh Tao, with hard corals making up and average of only 19.8% of the substrate (and as little as 3.5%, at the 3m line). Coral competing macro-algae made up as much as 47% of the total substrate cover, the highest values ever recorded in 7 years of surveys around the island. The abundance of macro-algae and the lack of solid substrate are the most likely causes for the failure of the site to rebound following the mass bleaching events of 1998 and 2010. Future management of the area must incorporate measures directed at improving water quality by addressing land based sources of pollution before biological or structural restoration of the bay can be successful.
Chad Scott, New Heaven Reef Conservation Program, 2014.
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