Sea Sawdust Causes Water Discoloration in Vung Tau

Photo courtesy of VN Express

Beaches in Vung Tau, Vietnam, experienced significant discoloration from a bloom of Trichodesmium erythraeum, or "sea sawdust," between April 4 and 5. The phenomenon resulted in a matcha-green tint to the water, a pinkish film, and a foul smell that alarmed visitors. The situation returned to normal by April 10 after marine debris was observed.

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The Vung Tau Ward People's Committee reported their findings to Ho Chi Minh City's relevant departments. An analysis conducted by the Vietnam Academy for Water Resources revealed Trichodesmium erythraeum dominated the bloom, contributing to over 99.53% of the biomass. Known for fixing nitrogen in tropical oceans, this cyanobacterium often releases pink pigments, leading to such discolorations.

Although not dangerous, contact with dense algal mats can cause mild skin and respiratory irritation. Comparable events have occurred globally, and advisories typically suggest avoiding scummy waters. Past discoloration events in Vung Tau have involved different species, such as Noctiluca scintillans in 2025.

The recent bloom was attributed to seasonal factors, including hot weather and reduced ocean mixing. Nutrient-rich runoff from local rivers, combined with calm conditions, created an environment conducive to rapid cyanobacterium growth. Vung Tau, a popular tourist destination, saw these blooms enhanced by local and climatic influences.

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