Red tide bloom can affect your health

Red tide cells
Karenia brevis (red tide) cells - Mote Marine | Submitted

ANNA MARIA ISLAND – Scratchy throats, itchy eyes and coughs persist with the continuing red tide that showed up on Friday, Aug. 3 in Anna Maria Island waters, thanks to winds and currents carrying the long-lasting bloom from Southwest Florida.

The Karenia brevis red tide organism is a type of algae that emits a neurotoxin when it blooms. Deadly to fish, sea turtles, marine mammals and shorebirds that feed on affected fish, red tide also makes shellfish unfit to eat and can cause respiratory irritation in people, especially those with asthma, COPD or other respiratory diseases. People with these conditions are advised by public health officials to stay away from the beach during red tide outbreaks.

One of the most frequent symptoms people experience during a Karenia brevis red tide is respiratory irritation. If you have ever visited a beach during a red tide, you may have experienced the “red tide tickle” which can include itchy throat and coughing. Brevetoxins, chemicals produced by Florida red tide, may also irritate pre-existing respiratory conditions including asthma. Persons with asthma are advised to bring their inhaler to the beach during a red tide or avoid the area until conditions improve. Some swimmers experience skin irritation and rashes after swimming in waters with a severe red tide. They have also reported eye irritation from the sea foam. In some red tides, dead fish wash ashore; during these conditions it is advised that beachgoers avoid swimming in water where dead fish are present. – Florida Department of Health

For months, Florida communities south of Anna Maria Island have been experiencing effects from red tide, which has persisted in the Gulf of Mexico since November 2017, impacting the commercial fishing industry and tourism-related businesses like vacation rentals, restaurants and fishing charters.

Toxins from the current bloom have caused large-scale fish kills and sickened or killed marine mammals, including manatees, an imperiled species, and at least one whale shark.

Studies on red tide have linked blooms to fertilizer runoff; fertilizer application is prohibited locally by law in summer months.

No effective method of eliminating red tide, a natural phenomenon, has been discovered, however, Mote Marine Laboratory is experimenting on several possibilities:

  • Ozonation to be used to destroy red tide algae and their toxins in limited areas of water such as canals and small embayments in Boca Grande.
  • “Living dock” structures covered with filter-feeding animals that remove red tide from limited areas of water such as canals and small embayments.
  • Concentrating naturally produced compounds from certain macro-algae (seaweeds) to be used to fight red tide blooms in the wild, considering that these compounds can kill red tide in the lab.
  • Use of algae in the Amoebophrya genus to serve as a natural control parasite for Karenia brevis red tide blooms.

Shellfish like clams, oysters, and coquinas that are harvested from areas with active red tides should not be eaten. These shellfish are filter feeders that can concentrate the toxins. Scallops can be consumed if only the scallop muscle is eaten. Scallop stew, using the whole animal including guts, should not be eaten. Seafood, also commonly called shellfish such as crabs, shrimp, and lobster can be eaten because they do not concentrate the toxin. – Florida Department of Health

Methods of predicting where red tide is and where it will go also are being developed.

  • The National Oceanic and Atmospheric Administration provides forecasts of potential respiratory irritation.
  • Mote is developing a new, improved version of its red tide detection instrument originally created more than a decade ago. The new Programmable Hyperspectral Seawater Scanner (PHYSS) detects red tide in seawater with higher resolution than ever before.
  • Mote research is currently developing hand-held sensors for local shellfish growers to use to document state and federal health agencies whether their cultivation waters and/or shellfish product contain red tide toxins. This would help to lessen the negative economic impact to these growers if there is red tide in the general vicinity but no toxin in their shellfish.
  • Mote’s smartphone app, CSIC (Citizen Science Information Collaboration), allows people along the Gulf of Mexico coast to report dead fish, respiratory irritation and discolored water: all potential impacts of red tide. With reports from beachgoers, the app helps to fill gaps in the existing beach monitoring programs and give the public a better idea of which beach to choose on a given day.
  • Mote scientists are exploring how to advance aerial monitoring of red tides using drones carrying hyperspectral cameras for finer-scale data collection than satellite images can provide. Unlike satellites, drones will be less impeded by cloud cover.

Updated information on red tide is available at:

More red tide information:

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