Certain chemicals in sunscreen products are to blame for the death of more than half of the corals at the famed Maya Bay on Phi Phi Island in Krabi, said Songtham Suksawang, director of the National Park Office.
The renowned bay has been closed indefinitely since Oct 1 due to extensive damage caused by an overwhelming number of visitors.
Citing findings from a study by the team leading the rehabilitation operation, Mr Songtham said the chemicals in visitors' sunscreen products were the main factor in the destruction of corals.
"The chemicals cause corals to bleach. In the worst cases, they even paralyse or kill the corals," he said.
Other factors attributed to the damage to Maya Bay's corals are the anchors and propellers of the many tourist boats which ply the sea.
"Several thousand litres a day of polluted water are discharged by tourist boats, which also poses a direct threat to the survival of the corals," Mr Songtham added.
"Maya Bay is like a patient who needs plenty of time to recover from an illness after an operation," said Asst Prof Datchani Emphan, an academic from Kasetsart University's Faculty of Forestry.
Chongkhlai Wongphongsathon, deputy director-general of Department of National Park, Wildlife and Plant Conservation (DNPWPC), said the bay is closed every year for four months to allow time for environmental recovery.
However, although the bay was supposed to reopen on Oct 1, the department decided to keep it closed indefinitely after learning about the substantial damage.
Mr Chongkhlai confirmed that more than 51% of the bay's corals has been affected.
He was speaking while leading a team of academics and DNPWPC officials to survey the area yesterday.
Mr Chongkhlai said that during the closure, tourists are allowed to take a boat trip to observe the natural surroundings of the bay from about 250m to 300m away from it.