What Is a Red Tide and What Are Its Effects?

Many of the large news headlines are covering the effects of a long and deadly algae bloom in southwest Florida. Dead marine life is cluttering the beaches, leaving many beachgoers meandering around carcasses. The dead marine animals include fish, sea turtles, birds, sharks, and manatees. Scientists just call it a harmful algae bloom, but many people call it a red tide. If you have not heard of it before, we are here to fill you in on what a red tide is and its effects on the environment.

What Is a Red Tide?

A red tide, or harmful algae bloom (HAB), occurs when ocean conditions are just right for algae to bloom. Too much of it blooms, so it has a negative impact on its surroundings. In Florida, the culprit of a red tide is Karenia brevis, or K. brevis. It is a type of algae that is almost exclusive to the Gulf of Mexico, but scientists have also found it in the waters on Florida’s east coast and off the coast of North Carolina.

Other Facts About a Red Tide

When an HAB occurs, some people who are new to the term still have questions about what the phenomenon actually is. Here are other facts to help you inform yourself as you read about Florida’s current struggle.

  • When the concentration of algae is high, the water can turn a variety of colors. Sometimes it is red, and other times it is dark or light green, brown, or clear.
  • The first red tide was recorded in 1844.
  • Algae is a beneficial part of the ocean’s ecosystems. They produce food and energy for the other animals.
  • Algae produces a toxin that is harmful in high concentrations, affecting the central nervous systems of the animals around it.
  • A red tide can last a matter of days, or it can last weeks and months. There are even some records of a red tide lasting a year. The science predicting how long red tides last is limited.

How Does It Affect Health?

Just because there is a red tide, it does not mean you are not allowed to go swimming. If there are dead fish nearby though, avoid swimming. You also should not swim if your skin is easily irritated. If the algae irritates your skin while swimming, be sure to thoroughly wash your body with fresh water.

A red tide can also cause the following:

  • Burning eyes
  • Tearing eyes
  • Coughing
  • Sneezing

You can lessen the effects by wearing a particle filter mask or taking an over-the-counter antihistamine (allergy medication). If you suffer from asthma, you should avoid the affected area, especially when the wind is blowing the toxins toward the shore. If you choose to go anyway, take an inhaler with you.

Can You Still Eat Seafood?

If you purchase seafood from the grocery store or a restaurant, the food is safe to eat. It is closely monitored by the government, so you will not be ingesting any tainted seafood. Eating seafood obtained by recreational fishing is another matter. Do not eat clams or oysters, but you can eat fish if you fillet it. Shrimps and crabs are unaffected by the toxins and are safe to eat.


This red tide in Florida is the longest one since 2006, which was after Hurricane Katrina hit. This current one is going on nine months long, and scientists are unsure when it will end. Make sure you are prepared if you plan to take a trip to Florida anytime soon and remember to be careful.

Image Source: Pixabay

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Lacey Jolley

I love exploring, experiencing new places, and eating good food! I'm amazed every day at how well the Earth provides for us, and I want to return the favor. I hope to help others learn how we can make our world a better, cleaner place.

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