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Basic information on red tide

What is red tide?
A red tide, or harmful algal bloom, is a higher-than-normal concentration of a microscopic alga (aquatic plant). In Florida and the Gulf of Mexico, the species that causes most red tides is Karenia brevis, often abbreviated as K. brevis.

Why are red tides harmful?
Many red tides produce toxic chemicals that can affect both marine organisms and humans. K. brevis produces toxins that can affect the central nervous system of fish and other vertebrates, causing these animals to die. Wave action can break open K. brevis cells and release these toxins into the air, leading to respiratory irritation in humans. For people with severe or chronic respiratory conditions, such as emphysema or asthma, red tide can cause serious illness. The red tide toxins can also accumulate in filter-feeding mollusks such as
oysters and clams, which can lead to Neurotoxic Shellfish Poisoning in people who consume
contaminated shellfish.

Read more about red tide...

Red tide health tips

  1. Most people can swim in red tide, but it can cause skin irritation and burning eyes. If your skin is easily irritated, avoid red tide water. If you experience irritation, get out and thoroughly wash off with fresh water. Swimming near dead fish is not recommended.

  2. Symptoms from breathing red tide toxins usually include coughing, sneezing, and teary eyes. For most people, symptoms are temporary when red tide toxins are in the air. Wearing a particle filter mask may lessen the effects, and research shows that using over-thecounter antihistamines may decrease your symptoms. Check the marine forecast. Fewer toxins are in the air when the wind is blowing offshore.

  3. People with chronic respiratory problems like asthma and COPD should avoid red tide areas. If you have symptoms that persist, seek medical attention.

Red tide monitoring and reports

Mote Marine Laboratory and the Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute (FWRI) continuously monitor area waters for K. brevis, the organism that causes Florida red tide.

Mote Marine Laboratory beach reports

Fish and Wildlife Research Institute Current Status



Red tide links:

If you have a question or a health problem related to red tide, please call the Florida Department of Health in Charlotte County, Environmental Health Division at 941-743-1266.

Beach Condition Reports:
Mote Marine Laboratory beach reports


Environmental Health Main Page

For information after business hours please call 941-624-7200.

Department of Health Mission: To protect, promote & improve the health of all people in Florida through integrated state, county, & community efforts.

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