Facebook user ‘Tonya So Say’ on Wednesday posted a 14-minute video on the group Siang Prachachon Khon Phuket (‘The Voice of Phuket Citizens’) with the caption:

“There is oil spreading on Karon Beach and tourists are unable to swim. This has also impacted many hotels and businesses along the beach. How can I inform officials about this problem?”

The video was shared by several other users, who called for authorities to take action.

Marine Office Chief Surat Sirisaiyas inspected the site and responded that the supposed ‘oil spills’ were actually plankton blooms.

“The plankton is not widespread; it only appears in some spots and then disappears again,” said Surat.

He insisted that the bloom was caused by heavy winds and that tourists need not worry.

“Everyone can swim normally. We just want people to be careful and avoid those spots. We have lifeguards on the beach to guide and warn people with red flags,” Surat added.

Dr Pornsri Suthanaruk, director of Regional Environmental Office 15, said that her office had received similar complaints about brown water at Karon Beach last week and that they were awaiting results of laboratory tests to ensure that it was safe.

“Plankton blooms are often caused by excessive amounts of nutrients in the form of nitrogen and phosphorus,” she said.

The reason for the presence of excessive nutrients in the water in the first place, however, does lead back to wastewater from local sewers, as Patong Mayor Chalermluck Kebsup told the Phuket Gazette in February.

Mayor Chalermluck had also revealed a tentative solution to counter the plankton, which was to grow eichhornia crassipes (better known as water hyacinths), but no implementation timeline or any confirmation of its effectiveness has yet been forthcoming.