Marine biologists concerned over dying reefs at Koh Lanta
Plankton boom blamed for losses
By Apinya Wipatayotin

Marine biologists have played down concerns of severe degradation of soft coral reefs at famous diving sites in Krabi's Koh Lanta, saying the coral might recover naturally within two years. The massive death of soft, multi-coloured coral reefs at Hin Muang and Hin Daeng diving sites earlier this month worried marine biologists and divers as the sites were one of the country's most famous for diving, thanks to the healthy condition of the reefs and abundant marine life.
The two coral reefs are less than one kilometre from each other in the Koh Lanta Marine National Park.

State marine biologists rushed to investigate the degradation and concluded last week that the death of the coral resulted from oceanographic changes, particularly a boom in plankton.

Somkiat Khokiattiwong, head of the Department of Marine and Coastal Resources' oceanography and environment unit, said a plankton boom was to blame for the massive death of soft coral that blankets undersea rocks at the Hin Muang and Hin Daeng diving sites.

Such phenomenon also killed coral reefs off Phuket, Phi Phi island in Krabi and the Tap Lamu sea in Phangnga.

A plankton boom occurs when an unusually high amount of cold current flows into coastal areas. The cold current is usually full of nutrients that make plankton grow rapidly. A plankton boom leads to a sharp drop of oxygen dissolvent to a level that is too low for marine life to survive, he explained.

''Our survey found that 100% of soft coral at Hin Muang and 50% of Hin Daeng were destroyed,'' said Mr Somkiat, adding that there has been no sign of coral recovery at the sites.

Niphon Phongsuwan, a marine biologist at the Phuket Marine Biology Centre, said nothing could be done to revive coral damaged at the famous diving sites.

However, he believed the coral reefs would be able to recover naturally within two years if there were no further disturbances to the site.

''Soft coral takes a shorter time to recover, compared with other kinds of coral. So what we can do at the moment is just let nature do its own job and prevent human activity from intervening in the natural rehabilitation process,'' said Mr Niphon.

But if there are no signs of recovery within two years, it means the soft coral will not be able to grow again, he said.

Thon Thamrongnawasawat, a marine scientist from Kasetsart University, expressed concern over the loss of soft coral at the reefs as well as other sites in Thai waters due to uncontrolled tourism activities.

He said the influx of tourists and divers, coupled with oceanographic changes, posed a severe threat to marine life.

Bangkok Post