Extreme plankton bloom creates 'dead zone' off Thailand

STORY: Location: Chonburi, Thailand

This patch of ocean, off the eastern coast of Thailand, has been dubbed a 'dead zone.'

According to researchers, no animals can survive here due to the growth of plankton.

While normal amounts of the organisms can be beneficial, the overwhelming bloom has reached harmful levels, depriving marine life of food and oxygen and turning the seawater green for as far as the eye can see.

“We see that the area with hypoxia (low oxygen level) or anoxia (no oxygen) has spread to a large scale, the dead zone where there's no oxygen is extensive. This is the single reason to explain the massive number of stranded dead fish.”

Tanuspong Pokavanich is a marine scientist from Kasetsart University.

He and a team of scientists have been collecting water samples to see what type of plankton has been growing.

The water is dense and slimy - as a pungent smell of grass and dead fish permeates the air.

Plankton covers a quarter of the Gulf of Thailand.

Half of it is green where the plant is thriving, while the other half, closer to the shore, has turned brown, or even darker from pollution and dead plankton.

[Tanuspong Pokavanich, Marine scientist, Kasetsart University]

“The plankton in the water eats up all the nutrients or dies due to a lack of light. Their carcasses will then sink to the seabed and are decomposed by bacteria. The bacterial decomposition depletes oxygen in the water. This, known as the process of eutrophication, is occurring and causing a vast number of fish to die.”

For local fishermen, the loss of marine life is a threat to their livelihoods.

There are more than 260 mussel farming plots along this coastline.

More than 80 percent have been severely impacted by the plankton bloom, according to the Chonburi Fisheries Association.

Suchat Buawat is one of those to have been affected.

In the business for more than 20 years, he owns about ten farming plots, and says he's seen losses of more than $14,000 since the start of the year.

[Suchat Buawat, Fisherman]

“The damage appears to be 100 percent. See, they just fall off when you shake it. There are no live ones left. They're all dead, including the oysters. Normally, they would cling on here as well."

Back in the lab, Tanuspong’s team has discovered the current plankton bloom is of the Noctiluca species.

That's the same species that bloomed in 2020 - the last time the region saw the El Nino effect.

The climate pattern causes, amongst other things, warmer sea temperatures in the eastern Pacific Ocean.

Tanuspong wants to study whether the two are linked.

Source: European Union's Copernicus Climate Change Service

In August, the global ocean saw the warmest daily surface temperature on record, and had its warmest month overall.

[Tanuspong Pokavanich, Marine scientist, Kasetsart University]

“Everyone now agrees that the El Niño that occurred somewhere in the distance in the Pacific Ocean now has a chain reaction on Thailand. El Niño causes drought and higher sea temperatures. El Niño is predicted to have a severe impact this year and people have been drawing conclusions that there may be links as it coincides with the significant amount of plankton bloom. However, from a scientific perspective, we have not reached a clear conclusion. We only see that both events occurred at the same time."

While the cause of the intense plankton bloom remains unclear, scientists believe pollution and the intense heat caused by climate change are to blame.