Red Tide: All you need to know about a type of harmful algal bloom

Red Tide occurs during summer and spring when the sunshine is apt. (Photo credit: Pixabay)

Red Tide occurs naturally in the Gulf of Mexico and appears to be exacerbated by the presence of nutrients such as nitrogen.


  • Red Tide is the discolouration of seawater usually caused by dinoflagellates.
  • Symptoms from breathing red tide toxins usually include coughing, sneezing, and teary eyes.
  • Red Tide is currently blanketing the Southwest Florida coast.

New Delhi: Red Tide bloom was detected near an island in the Lower Florida Keys this week, ruining the beach experience for many tourists. According to reports, the red tide bloom killed tons of fish and other animals including loggerhead sea turtles and manatees. Concerned about the issues, the Florida Fish and Wildlife Conservation Commission advised people not to swim or go near brownish waters since it can cause skin irritation, rashes, burning, and sore eyes. Those with asthma and respiratory problems should not visit the beach at all.

What is Red Tide?

Red Tide is a sea-faring toxic algae, formally known as the single-cell Karenia brevis. It produces a toxin as a defence mechanism. Red tides are a natural phenomenon. Since the 1800s, they have been observed in the Gulf of Mexico.


Red Tide occurs when the population of certain kinds of algae known as dinoflagellates explodes, creating what is called an “algal bloom”. Scientists sometimes refer to red tides as harmful algal blooms or HABs.

Is Red tide harmful to humans?

People who inhale the red tide toxin may experience respiratory symptoms like coughing, wheezing and sore throats.

It is a killer that harms the nervous system and has the potential to paralyse marine life.

How to stay safe from red tide?

If you have been recently exposed to a Red Tide, wash your skin and clothing with soap and clean water.

Keep animals away from the water, sea foam, and dead marine life.

If your pet swims in these waters, wash them immediately.

Do not consume shellfish or distressed or dead fish.

Those with chronic respiratory issues should be especially cautious near the water, as the red tide can affect breathing.


Red tide blooms can last days, weeks, or months and can also change daily due to wind conditions and water currents.

Onshore winds normally bring it near the shore and offshore winds drive it out to sea.

In Florida, Red Tide is caused by a naturally occurring microscopic alga (a plant-like microorganism) called Karenia brevis.

The organism produces a toxin that can affect the central nervous systems of fish, birds, mammals, and other animals.

At high concentrations (called blooms), the organism may discolour the water — sometimes red, light or dark green, or brown.

Red Tides or harmful algal blooms (HABs) occur worldwide.

Red Tide was first officially recorded in Florida in 1844.

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