Red tides are large blooms of certain kinds of algae – only a handful of the thousands of different species that make up the base of the food web in the ocean. Some harmful algae have a red pigment used to trap light and make food. When the plankton populations bloom, the millions of organisms turn the water’s surface red. Hence the name “red tide.”

Environmental conditions like warm, still waters, high nutrient levels, and low salinity can cause these harmful algal blooms. They produce a toxin that makes them taste bad to fish that would otherwise eat them. Although this chemical can even kill fish, medical experts say it only irritates humans. But the toxin can build up in shellfish. That’s why tainted shellfish are unsafe and possibly deadly for humans to eat.

When red tide is carried to shore by breaking waves, the salt spray carries red tide particles into the air. That can cause you to cough from breathing in the algae’s toxic chemical. Wind and waves will eventually disperse the bloom. Meanwhile, experts say the cough is only temporary. They add it’s best to avoid the beach during the time of a red tide if you have asthma.

Our thanks to:
Dr. Wayne A. Bennett
Assistant Professor of Biology
University of West Florida
Pensacola, FL

Dr. Dick Snyder
Assistant Professor of the Center for Diagnostics and Biomediation
University of West Florida
Pensacola, FL