"I've never seen anything like this before," breathes oceanologist Lalita Putchim after a dive off the island of Samae San, southeast of Bangkok.

Large yellow spots cover sections of the coral reef, victims of a killer bacterium which until now had spared this corner appreciated by amateur divers.

The spread of the so-called "yellow bands" disease, spotted in the province of Chonburi (southeast) for the first time in 2021, reminded Thailand of the fragility of its marine biodiversity, exposed to climate change.

In this tourist region, between the island of Samae San and Pattaya, scientists have found traces of dead coral in an area of ​​more than 2 km2, explains Lalita Putchim, who works for the department of marine and coastal resources, under the authority of the Ministry of Natural Resources and the Environment.

The rapid spread of the disease worries scientists all the more as no treatment is known to get rid of the bacteria, first observed in Florida in the 1990s.

Other questions remain about the arrival in Thailand of the disease, which could be linked to overfishing, pollution and the warming of sea water which weakens the structure of the coral, according to experts.

Coral samples show yellow bands, a sign of infection with a killer bacteria, on December 22, 2022 off the Thai island of Samae San © Lillian SUWANRUMPHA / AFP

Environmental protectors have organized their response on the ground, via dives to spot and collect diseased corals, and in laboratories, where researchers are trying to unravel the mysteries of the bacteria.

"So far, we only know the name of the bacteria that causes the disease," admits Sarawut Siriwong, a researcher specializing in aquatic environments at Boraphat University in neighboring Chanthaburi province.

It is necessary to accentuate the protection of coral reefs, by limiting the evacuation of waste water into the sea or to dissuade visitors from touching the corals, he assures.

Volunteer divers

But research comes up against a financial and human barrier, which restricts research and prevents any large-scale operation to contain the bacterium.

The authorities could decide to allocate special funds in 2023, Athapol Charoenshunsha, director general of the marine and coastal resources department, told AFP.

Marine biologists and volunteers examine yellow bands present on sections of coral reef victims of a killer bacteria, December 22, 2022 off the Thai island of Samae San © Lillian SUWANRUMPHA / AFP

"It's a very important subject. It's the first time that Thailand has encountered this disease, so we have to be very careful," he said.

In the meantime, the researchers are calling on volunteer divers to help them spot the destroyed reefs.

"I started helping...after I saw the abnormal color of the coral," said Thanapon Chaivanichakul, 38, a business executive from Bangkok, one of four volunteers helping the scientists that day. , taking pictures of underwater flora and fauna.

It is an entire region that is watching the precious corals disappear, one of its assets that attract Thai and foreign tourists in search of idyllic beaches and turquoise waters and which sustains the local economy.

Lalita Putchim (center), marine biology specialist, prepares to collect data on the yellow bands present on sections of coral reef victims of a killer bacterium, December 22, 2022 off the Thai island of Same San © Lillian SUWANRUMPHA / AFP

"It's as if our own house was destroyed," complained Choopan Sudjai, owner of a tourist boat offering tours of Samae San Island.

This 55-year-old man keeps his community up to date with the latest news on the disease.

"Everyone is more careful when they go to sea now," he says.

"But since the coral is infected, and will be destroyed, what are we going to do in five years?"

© 2022 AFP