Red tide in Hai Phong

Algae blooming with high density makes Cat Ba and Hai Phong waters appear "red tide", with red or pink scum layers on the water lasting more than a month.

>>>Green energy from the tide

Scientists from the Seafood Research Institute found that red tide phenomenon occurred in the coastal area of ​​Do Son - Cat Ba. After sampling and analyzing, Dr. Nguyen Van Nguyen, Deputy Director of the Institute of Seafood Research, said that the algae adjoining Noctiluca scintillans , the red strain is the cause of red tide in the coastal area of ​​Cat Ba.

Red tide is the common name for phenomena known as "blooming" seaweed outbreaks, which often occur in estuaries.

Red tide phenomenon, also known as "blooming" algae in the sea
Cat Ba, Hai Phong. (Photo provided by Dr. Nguyen Van Nguyen)

"From the end of March to the present, this algae has exploded with high density, creating floating water scum on the surface. The scum layer with color from light pink to red depends on the density and stage of development of algae" , Dr. Nguyen said.

According to Mr. Nguyen, due to tidal and flow interaction, some water bodies carry red tides drifting and staying in coastal areas, quiet bays, where they can continue to increase in density, creating thick layers of scum, causing dense red tidal bands in some puddles, docks, and boats along Cat Ba and Do Son islands.

Mr. Nguyen said that noctiluca scintillans does not produce toxins, so there is no risk of poisoning for humans or aquatic products. But they have the ability to accumulate ammonia in high concentrations and release it into the water environment. Their high density also causes the depletion of oxygen in the water body, which can cause death of aquatic products.

The Seafood Research Institute recommends that people should monitor and prevent negative impacts on aquaculture, especially in fish cage areas, concentrated in closed caves and bay. In the case of dense red tide bands covering fish cage farming households, the cage must be lowered to create space for fish to avoid red tidal water layer, about 3-5cm above the surface.

Red tide was first recorded in Hai Phong in June 2002. In the past year, the Seafood Research Institute discovered 3 red tide outbreaks in Cat Ba area.

Algae blooms can make the sea red, blue, or gray or rice bran.
Red tide when flooding on the coast of Binh Thuan. (Photo: Nha Trang Oceanography Institute)

In Vietnam, red tide phenomenon mainly occurs in the South Central Coast region than the Gulf of Tonkin and the South. In which Binh Thuan is a place with this phenomenon regularly, every year from March to September, especially during the southwest monsoon period.

According to Dr. Nguyen Ngoc Lam, Nha Trang Institute of Oceanography, who has many years of experience researching red tide, pre-existing seaweed in the sea, along with environmental factors, warm water, strong light can cause the phenomenon of algal blooms, creating a discoloration of water, called red tide, also known as "blooming" algae .

Dr. Lam warns, most algae blooms can make the environment worsen by reducing the amount of dissolved oxygen in the water, while also causing marine animals to die massively.