The sea suddenly turned bright red, then shifted to deep blue, and finally became as dark as sewage. Crabs and fish lay dead in droves, while corals turned white and died; seaweed and seagrass perished as well. Most marine life was wiped out. In the following days, a foul odor filled the air… This was the scene caused by “red tide” in Bình Thuận several years ago.
“Red tide” or the “bloom” of algae refers to the phenomenon of explosive algal growth in marine environments. The “bloom” can turn the ocean red, blue, gray, or even the color of rice husk… This phenomenon often accompanies a rapid decline in dissolved oxygen levels in the water, which is the main cause of death for many marine organisms both in natural habitats and aquaculture. According to Dr. Nguyễn Ngọc Lâm, a researcher at the Institute of Oceanography in Nha Trang, the spores of algae are naturally present in seawater, thus they can “bloom” anywhere conditions are favorable, such as increased temperature, poor water circulation, enhanced nutrient levels, or marine pollution…
Research results indicate that approximately 70 harmful algal species exist along our coastal waters. 
The “red tide” disaster in Bình Thuận in mid-July 2002 resulted in the destruction of about 90% of the organisms in the intertidal zone, including fish and shrimp in cages and rafts; the environment was heavily polluted and took months to recover. The “red tide” also caused 82 people to be hospitalized due to swimming in the sea, exhibiting symptoms such as itching and blistering of sensitive skin; this was caused by a species of blue-green algae that “bloomed” and released toxins into the seawater. It is important to note that blue-green algae blooms (cyanobacteria) also occur in many freshwater reservoirs, posing a health risk to those who use this water source.
There are also algal species that do not “bloom” but produce toxins; fish and bivalves that consume algae can accumulate these toxins in their bodies. To date, researchers have identified six symptoms of poisoning in humans caused by consuming species that accumulate algal toxins. These toxins are not destroyed during cooking and do not affect the taste of seafood. Therefore, consumers, including fishermen, often do not detect algal toxins in their food. 
In our country, the Center for Food Safety and Veterinary Hygiene (under the Ministry of Fisheries) is responsible for monitoring the safety of seafood (primarily bivalve mollusks) exported to the European market. However, many localities that farm green mussels and other bivalve mollusks have yet to prioritize this issue.
Dr. Nguyễn Ngọc Lâm believes that we can mitigate the damage caused by “red tide”, provided that adequate investments are made in fundamental research. The focus of this research should not only be on harmful algae but also investigate environmental factors such as physical and chemical properties, temperature, water flow, sources of wastewater, and socio-economic characteristics… Additionally, it is essential to educate fishermen that upon detecting signs of “red tide”, they should immediately report to the authorities, enabling necessary responses, such as relocating fish and shrimp cages or changing water in aquaculture ponds. Monitoring harmful algae in a small area (such as Florida Bay) in the United States costs millions of dollars each year. Annually, China also allocates a significant budget for research and monitoring harmful algae. In our country, investment in this area remains very modest.
