What is red tide? Is it dangerous?

Red tide, also known as algal bloom, is a phenomenon in which algae reproduce in large numbers in estuaries, seas or freshwater.

Depending on the type of algae, the surrounding seawater will be cloudy or turn pink, purple, red, black or blue.

Red tides are not necessarily red, but can also form many different colors (blue, black, pink, orange...). In particular, they are not related to tidal movements but are a form of algal bloom.

Natural red tides are algal blooms and are not related to tidal activity.

Causes of red tide

There are many causes of red tides. Here are the basic reasons:

• Due to high temperature, the oxygen content in water is reduced or the nutritional conditions in the water environment increase dramatically.
• Due to the strong blooms of non-toxic and toxic algae in the natural environment.
• Due to other factors such as iron-rich dust from vast deserts, related to large-scale climate change such as the El Nino phenomenon.

How long do red tides last?

Red tides can last for several weeks or even longer than a year.

Red tides are caused by algal blooms and are highly dependent on physical and biological conditions such as sunlight, nutrients and salinity, as well as the speed and direction of wind and currents. The phenomenon may subside and then reappear.

Red tides usually occur close to shore, but can occur 10-40 miles (16-64 km) offshore.

The harmful effects of red tide

The appearance of red tides is a sign of abnormality that can greatly affect the lives of humans, animals and plants globally.

• The red tide phenomenon greatly affects human health if we eat organisms infected with toxins.
• Red tides cause mass deaths of shrimp and fish in aquaculture areas, even disrupting the ecosystem and making the surrounding air much harder to breathe. This greatly affects income sources in particular and the economy in general.
• The process of decomposing non-toxic algae blooms will deplete the oxygen in the seawater, causing mass deaths of marine animals.
• The accumulation of too much seaweed in the water will form mucous membranes on the gills of fish, affecting the absorption of oxygen in the water.