Plankton bloom turns Thai holiday paradise green – and raises a stink
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Tourists swimming in green seawater amid a plankton bloom in Ko Lan, a popular tourist island in Thailand, on Oct 1.
PHOTO: REUTERS
- A plankton bloom caused by heavy rains and floods turned the sea around Thailand’s Ko Lan island bright green, deterring swimmers and affecting local beach vendors.
- Researchers identified the plankton as Noctiluca and noted that blooms, worsened by climate change and nutrient runoff, can create oxygen-poor ‘dead zones’ harmful to marine life.
- The bloom may be intensified by monsoons and El Niño, with recent severe flooding increasing freshwater flow into the Gulf of Thailand.
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KO LAN, Thailand – The sea off Thailand’s popular tourist island of Ko Lan turned a bright, pungent green this week as heavy rain and floods helped spark a plankton bloom that kept some swimmers on shore.
Dense patches of green could be seen stretching along parts of the coast, with jet skis floating in discoloured waters around the island in the northern part of the Gulf of Thailand. Other stretches of the shoreline were unaffected.
“What we’re actually seeing with the naked eye is a colour that comes from a type of plankton called Noctiluca,” said Arvut Munhapon, a senior researcher and head of marine environmental research at the Marine Science Research Division, Institute of Marine Science, Burapha University.
His team of four was on the ground collecting water samples, measuring water quality and bringing samples back to the lab to identify species and build a database to help provide a clearer picture of the situation.
Plankton blooms are a natural, recurring phenomenon, but they have worsened around the world as climate change has warmed seas, the researchers said.
Fertiliser run-off and nutrient-rich wastewater also wash into the sea and feed rapid plankton growth, they said.
Blooms typically last two to three days. When they end, mass plankton die-off consumes oxygen and sometimes creates hypoxic conditions, or an “aquatic dead zone”, with oxygen levels too low to support marine life, according to Anukul Buranapratheprat, deputy director of the Institute of Marine Science, Burapha University.
“We’re looking at the endpoint, which is hypoxia, and hypoxia in the inner Gulf of Thailand, based on my own research, has genuinely got more severe,” he said.
His biggest concern is a wide hypoxic zone that has formed, too low in oxygen to support bottom-dwelling marine life.
Monsoons and El Nino may be intensifying both the blooms and hypoxic conditions since warmer water holds less dissolved oxygen, but Anukul said more research was needed to confirm the connection.
Significant flooding has hit Thailand in recent weeks, including in central provinces and Bangkok, adding to the volume of fresh water reaching the gulf.
Food vendors along the beach said customer numbers had fallen since the green water appeared, with some visitors moving to unaffected areas of the island.
The discolouration was enough to keep others out of the sea altogether. Latipeya Thantibhapat, 29, a tourist from Chiang Mai, said: “I felt that it was unusually green compared with normal seawater, so I didn’t dare go in. I was afraid I’d break out in a rash.” REUTERS