Green Plankton Bloom Turns Ko Lan Waters Bright Green

Heavy rains and flooding this week have triggered a dense bloom of the bioluminescent plankton *Noctiluca* off Thailand’s tourist island of Ko Lan, turning sections of the northern Gulf of Thailand a vivid, pungent green. The discoloration has kept many swimmers on shore, while jet skis continue to navigate the tinted waters.

The Straits Times

Researchers from the Marine Science Research Division, Institute of Marine Science, Burapha University identified the bloom as a rapid proliferation of *Noctiluca* plankton. They note that such blooms are natural but have become more frequent worldwide as warming seas linked to climate change provide favorable conditions. Fertiliser runoff and nutrient-rich wastewater entering the Gulf also supply the nutrients that fuel the growth. The bloom typically persists for two to three days; when it ends, massive die-offs can deplete dissolved oxygen, creating hypoxic “dead zones” that threaten bottom-dwelling marine life.

The Independent

Arvut Munhapon, senior researcher and head of marine environmental research at the institute, explained that the visible green colour is caused by *Noctiluca* plankton. Anukul Buranapratheprat, deputy director of the Institute of Marine Science, warned that the hypoxic zone in the inner Gulf has become “more severe” based on his own research and that monsoons and El Niño may be intensifying both the bloom and the resulting low-oxygen conditions, though further study is needed.

The IndependentThe Straits Times

Beachside food vendors report a noticeable drop in customer numbers since the water turned green, with some tourists opting for unaffected parts of the island. Latipeya Thantibhapat, a 29-year-old visitor from Chiang Mai, said she avoided swimming because the water looked “unusually green” and she feared a rash. The discoloration has therefore reduced beach activity and altered visitor patterns on the island.

The Independent

• “What we’re actually seeing with the naked eye is a colour that comes from a type of plankton called Noctiluca,” — Arvut Munhapon

The Straits Times

• “We're looking at the endpoint, which is hypoxia ... and hypoxia in the inner Gulf of Thailand, based on my own research, has genuinely gotten more severe,” — Anukul

The Independent