(Baonghean.vn) - The sea water suddenly turned bright red, then dark blue, then black as sewage. Crabs and fish died everywhere, corals died and turned white; seaweed and seagrass also died.

Red tide or algal bloom is the name given to the phenomenon of an explosion in the number of seaweeds. The "bloom" of algae sometimes turns the sea water red, sometimes blue, gray or like the color of rice bran...

The "bloom" phenomenon is often accompanied by a rapid reduction in oxygen content in the water, and is the cause of the death of many marine species in nature and aquaculture.

Red tide is a form of algal bloom that is harmful to the environment due to the toxins of the algae themselves, and the decomposition of bacteria on the algae biomass, which then depletes O2 in the area.

Harmful algal blooms are collectively known as HABs.

Algal blooms in water bodies in general (lakes, rivers, seas...) are caused by many different types.

Only at extremely high densities (millions of cells/ml) does the water color change due to the pigmentation of the dominant species (from green to yellow-brown to red...).

Red tide is a phenomenon that occurs annually in the US, especially on the Florida coast (Gulf of Mexico) due to the Karenia brevis algae species belonging to the Dinoflagellate group with a density of up to tens of millions of cells/ml.

In the northwestern United States, especially in the Gulf of Maine, red tides are caused by another species of Dinoflagellate (Alexandria fundyense).

Red tides cause serious environmental damage because algae secrete neurotoxins. Karenia brevis in Florida secretes brevetoxin, and Alếandria fundyense secretes saxitoxin.

The main cause of algal biomass outbreaks is environmental eutrophication, because the main nutrients of algae are Nitrate & Phosphate.

These are substances found in human domestic and industrial wastewater, fertilizers, washing powders...

Red tide killed the entire clam farm in Cat Ba (Hai Phong) in 2012.

The sea water suddenly turned bright red, then dark blue, then black as sewage. Crabs and fish died everywhere, corals died and turned white; seaweed and seagrass also died. Most of the marine life was destroyed. In the following days, a foul stench arose….

This phenomenon is extremely sudden, difficult to predict and dangerous, causing great impacts on humans and aquaculture activities./.

Ha Chi

( Synthetic)