“Red tide” or the “bloom” of algae refers to the phenomenon of explosive growth in marine algae. The “bloom” of algae can sometimes turn the sea water red, and at other times blue, gray, or even the color of rice bran…
The phenomenon of red tide.
Red tide is generally not related to the movement of tides; therefore, scientists often prefer to use the term “algal bloom” to describe this phenomenon. Red tide does not necessarily change the color of the water when the concentration of algae is not too dense.
The phenomenon of “bloom” is often accompanied by a rapid decrease in oxygen levels in the water, which is the main reason for the death of many marine species in nature and aquaculture. According to Dr. Nguyen Ngoc Lam, a researcher at the Institute of Oceanography in Nha Trang, the spores of algae are already present in seawater and can “bloom” anywhere when conditions are favorable, such as increased temperatures, poor water exchange, or increased nutrient conditions in the environment, or marine pollution…
Depending on the type of algae, red tide can produce natural toxins, deplete oxygen, and cause other harmful effects. Scientists refer to this as “harmful algal bloom” (HAB). The most visible harm of HAB is the mass death of marine animals, including fish, crustaceans, mollusks, and other organisms.
This phenomenon can occur at any time if favorable conditions arise, such as a sudden increase in temperature or poor water exchange, or a dramatic increase in environmental nutrients.
Research results indicate that there are about 70 species of harmful algae along our coastline. Among them, the bloom of Phaeocystis globosa often occurs in the waters of Binh Thuan and lasts for about a month.
It is important to note that the “bloom” of cyanobacteria also occurs in many freshwater reservoirs, threatening the health of those who use this water source.
Other factors, such as iron-rich dust from vast desert regions like the Sahara Desert, are believed to play a significant role in causing red tide. Some instances of red tide occurring in the Pacific have been linked to large-scale climate change, such as El Niño.
The San Diego River in California, USA turns bright red due to the effects of red tide. (Photo: Kai Schumann/OceanService.gov)
There are also non-blooming algae that produce toxins; fish and bivalves that consume these algae will accumulate toxins in their bodies. To date, researchers have identified 6 symptoms of poisoning in humans caused by consuming species that have accumulated algal toxins. Red tide has the potential to harm human health if contaminated organisms are consumed.
These toxins are not destroyed during cooking and do not affect the taste of seafood. Therefore, consumers, including fishermen, may 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 seafood safety (primarily bivalves) exported to the European market. However, many localities that cultivate green mussels and other bivalve species have not yet prioritized this issue.
The impact of red tide on marine organisms is extremely serious. In aquaculture areas, it leads to mass deaths of shrimp and fish, disrupting the ecosystem. The surrounding atmosphere also becomes more difficult to breathe.
Additionally, in cases where non-toxic algae bloom and then die, their decomposition process will deplete oxygen in seawater, causing mass deaths of marine animals.
Dr. Nguyen Ngoc Lam believes that we can mitigate the damage caused by “red tide” by adequately investing in fundamental research. The research subjects here should not only focus on harmful algae but also investigate factors affecting the marine environment such as physical and chemical properties, temperature, currents, wastewater discharges into the sea, and socio-economic characteristics… Moreover, it is necessary to educate and inform fishermen that when they detect signs of “red tide”, they should immediately report to the authorities, so that necessary solutions can be implemented, such as relocating shrimp and fish farms or changing water in aquaculture ponds…
Monitoring harmful algae in a small area (such as Florida Bay) in the USA costs millions of USD each year. Annually, China also allocates a large budget for researching and monitoring harmful algae. In our country, investment in this field is still very modest.
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