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Living with Red Tide

This information is summarized from “Florida Red Tide“, by Libby Carnahan, Florida Sea Grant

There is a current bloom of Florida Red Tide in the Northeastern Gulf of Mexico. Are you concerned? Should you be? Whether you are planning an offshore fishing excursion or a family day at the beach, it is good to stay informed about local beach and water conditions.


Photo Credit: FWC, Karenia brevis

Red Tide is an example of a Harmful Algal Bloom (HAB)- a higher-than-normal concentration of a toxic or nuisance microscopic alga (plantlike organism) that negatively affects natural resources or humans.  The microscopic algae responsible for Florida red tide is Karenia brevis, pictured here. Red tide in Florida is a natural phenomenon, originating 10-40 miles offshore. In contrast to the many red tide species that are fueled by nutrient pollution associated with urban or agricultural runoff, there is no direct link between nutrient pollution and the frequency or severity of red tides caused by K. brevis.

The Florida red tide organism, K. brevis, produces brevetoxins that can affect the central nervous system of fish and other vertebrates, causing these animals to die. The red tide toxins can also accumulate in molluscan filter-feeders such as oysters and clams, which can lead to Neurotoxic Shellfish Poisoning in people who consume contaminated shellfish. However, Commercial seafood found in restaurants and grocery stores is safe because it comes from red tide free water and is monitored by the government for safety.

Red tide also causes respiratory irritation in humans as K. brevis cells release toxins into the air as they are broken down by wave action. For people with severe or chronic respiratory conditions, such as emphysema or asthma, red tide can cause serious illness.

Some precautions to avoid disease and/or discomfort due to red tide HABs include:

  • Stay away from the water where HAB conditions have been identified or if water is foamy or discolored or contains dead fish.
  • Do not eat, use or collect any fish, shellfish, other life or items from those waters.
  • Do not let pets swim in or eat fish from those waters.
  • If contact is made with the water, rinse as soon as possible with fresh water.
  • If you suffer respiratory discomfort when near the water, moving a short distance away from the shore may alleviate the symptoms. In more severe cases, stay indoors in air-conditioned rooms as much as possible.

A weekly Status Report is published by the Florida Fish and Wildlife Research Institute (FWRI) each Friday. The report includes state and regional maps.

The Beach Conditions Reporting System, maintained by Mote Marine Laboratory, is a user-friendly web interface that provide real-time conditions of our local beaches. The web portal enables you to register for email alerts for your choice of southwest Florida counties. During a red tide event, information includes:

  • If dead fish are present
  • Whether there is respiratory irritation among beachgoers
  • Water color
  • Wind direction
  • What warning flags are flying at lifeguard-monitored beaches

Health and Safety information on HABs

Centers for Disease Control and Prevention

Florida Department of Health

Florida Department of Agriculture and Consumer Services

Additional Resources

Mote Marine Laboratory, Florida Red Tide FAQs

Florida Fish and Wildlife Research Institute Red Tide Page