On May 17, social networks spread many photos and videos recording strange scenes at Hon Gai beach, Hong Ha ward, Ha Long city. The sea surface near the shore turns pink red and when there is a foot acting effect, the water immediately becomes magically green.
Previously, a similar phenomenon had appeared in the sea around Cat Ba Island (Hai Phong), attracting a large number of people and tourists to "hunt" for the moment the star lantern sea lit up blue at night.
Talking to Lao Dong Newspaper reporter, Doctor of Ocean Biology Dang Do Hung Viet (Nha Trang City, Khanh Hoa) said that the phenomenon of blue sea water when it has impacts such as footsteps, waves hitting the shore, rowing boats is due to the appearance with high density of the riverbeat species scientifically named Noctiluca scintillans, also known as the photoalgae.
Noctiluca scintillans is a single animal belonging to the dinoflagellate group, measuring from 0.2 to 2 mm, large enough to be observed with the naked eye when concentrated in large quantities.
This algae glides thanks to a bio-reducing mechanism: when chemically stimulated, the enzyme luciferase in algae breaks down the luciferin, thereby creating a characteristic blue light.
In the dark sea environment, millions of Noctiluca cells glow simultaneously, creating a very impressive "shellow sea" effect. This phenomenon has been recorded in many sea areas around the world such as the Maldives, Puerto Rico, Japan and even in Vietnam, especially in the summer when the sea water is rich in nutrients and the temperature rises.
Along with the phenomenon of photoalgeopods, there is often a phenomenon of red tides - sea water turning red, brown or orange due to the sudden increase in the density of filanthropes.
Although red tides are often associated with toxins, not all algae that cause them are toxic. Noctiluca scintillans often do not produce toxins, however, when they grow in too high a density, the phenomenon of red tides still occurs due to the color of the algae reflecting on the sunlight.
According to Dr. Viet, in general, Noctiluca phlegm algae do not directly cause poisoning to humans. However, if the phenomenon persists and the algae density becomes too dense, the algae will die simultaneously, leading to organic decomposition and consuming a large amount of soluble oxygen in the sea water.
This can cause oxygen deficiency (hypoxia), causing fish and bottom creatures to suffocate. In addition, the process of breaking down algae can also give off a foul smell or unpleasant compounds.
The cause of this phenomenon is often related to a sharp increase in nutrients in seawater, especially oxygen and phosphorus. Sources such as domestic wastewater, untreated boat washing water, warming water surface, calm sea water with little disruption and prolonged sunlight increase all create favorable conditions for algae to thrive.
In closed coastal areas such as Ha Long Bay, where there are many residential activities and sea traffic, these factors easily converge and cause cyclical phenomena to appear throughout the year.
This is a natural phenomenon of interest and is largely not dangerous if it does not last too long. However, experts recommend that you should monitor closely if the phenomenon occurs frequently with high density because it can be a sign of ecological imbalance along the coast due to malnutrition or localized pollution.
Regular observation, analysis of water samples, measurement of algae density, salinity, temperature and soluble oxygen are very necessary to control and protect the marine environment. Authorities also need to clearly propagate so that people and tourists can understand the true nature of the phenomenon, avoiding unnecessary confusion.
In short, the phenomenon of the blue sea shining in Ha Long is a natural phenomenon of the photoelectric algae, bringing a fascinating and non-toxic natural landscape. However, managing and monitoring the marine environment is still necessary to maintain a balanced and sustainable marine ecosystem.
