Reef Status of Shark Bay

Tien Og, also known as Shark Bay, is a favorite location for visitors to the island to observe Black Tip Reef Sharks, Sea Turtles, and other amazing reef animals. The area is a year round feeding and nesting ground for one of the Gulf of Thailand’s largest resident populations of reef sharks, which can be observed during the early morning and late afternoons. But while swimming with this sharks visitors will also see that something is not right with the reef, instead of being covered in coral like most the island, the area is covered in macro-algae growing on rubble.
Check out some amazing footage of the sharks in Tien Og, 2014 (shark footage starts at 2:33)

But this was not always the case in this area, in fact only 15 years ago the area was almost 100% covered by acropora branching corals, rising over a meter from the sea floor and providing refuge for millions of fish and invertebrates. In the highly complex structure created by the stands of branching corals supported a high amount of biodiversity and productivity, which is what most attracted the feeding sharks.


Juvenile Black Tip Reef Shark in Tien Og Bay, April 2014. Photo by Shin Arunrugstichai.

Juvenile Black Tip Reef Shark in Tien Og Bay, April 2014. Photo by Shin Arunrugstichai.

This all changed in 1998, when a worldwide mass coral bleaching event occurred, killing over 16% of the worlds reefs in a single hot season. The reef of Tien Og was all but destroyed in this bleaching event, suffering high levels of mortality amongst the fast growing corals. Subsequent to the bleaching, the delicate structure of the branching corals began to break up, leaving fields of moving rubble on which no new coral larvae could successfully recruit.


To compound the problem, rapid development and deforestation along the hillsides surrounding the once quite bay led to nutrient enrichment of the waters and paved the way for the succession of macro-algae. Macro-algae, or seaweeds, can easily out-compete slow growing corals when nutrients levels increase, creating beds of algae on which no corals will ever grow.


Today these effects are more obvious then ever, other areas impacted by the bleaching events of 1998 and 2010 have, to a large extent, recovered. But not in Shark Bay. In surveys completed by the NHRCP in March of 2014, fully 40% of the bottom is covered by macro-algae, while only 19.8% are covered by hard corals. Which begs the question, how much longer can the depleted reef withstand the effects of economic growth before collapsing completely?


On the link below you can download the full paper, published in April of 2014

Tien Og Baeline Paper, 2014



Recently, we have been asked by one of the resorts along the bay, Haad Tien, to assist in managing and restoring the area. Based on our findings in the area, restoration is going to prove impossible until water quality can be improved. Until development ceases, and land owners start to take proactive measures at reducing the erosion and release of waste water the coral reef will continue to waste away, being replaced by beds of ecologically and economically worthless algae.


Although the outlook for the area is less than optimistic, we are proud to be a part of its management, and proud of Haad Tien resort for steeping up to protect their marine resources while others continue to ignore them.  The road to recovery for this area will not be easy, but it is essential, this is an area worth protecting.