Red Tide’s toxic toll — your questions answered

The bloom of microscopic algae kills wildlife and causes respiratory problems for people.
This 26-foot-long whale shark washed up in Sanibel last month. Scientists suspect its death was linked to Red Tide, which has not yet menaced the Pinellas beaches the way it has the rest of the coast of Southwest Florida. [Florida Fish and Wildlife Conservation Commission]
This 26-foot-long whale shark washed up in Sanibel last month. Scientists suspect its death was linked to Red Tide, which has not yet menaced the Pinellas beaches the way it has the rest of the coast of Southwest Florida. [Florida Fish and Wildlife Conservation Commission]
Published Aug. 22, 2018|Updated July 14, 2021

A Red Tide algae bloom has been plaguing the Southwest Florida coast for months, and recently threatened to invade Tampa Bay (although the latest forecast shows it traveling southward again). Here are some questions and answers about the microscopic toxic threat to taking a fun trip to the beach.

What is Red Tide?

Small, scattered colonies of microscopic algae live in the Gulf of Mexico all year long. Usually their numbers are so tiny that no one notices. But every now and then, usually in the late summer or fall, the algae population 10 to 40 miles offshore explodes into something called a bloom. The algae multiply rapidly and spread across the water's surface, staining it a rusty color that gives the phenomenon its name. Then winds and currents carry it toward shore.

BACK STORY: Lingering Red Tide bloom moves north, killing fish near mouth of Tampa Bay.

Is Red Tide heading to Pinellas County's beaches?

Not so far. The latest report from the Florida Fish and Wildlife Conservation Commission and the University of South Florida shows only low or background concentrations of the algae in Pinellas waters, and predicts a southward movement of the bloom over at least the next three days. What happens after that is anyone's guess.

PREVIOUS COVERAGE: Recalling the devastating Red Tide of 2005 and dreading a repeat.

Is Red Tide related to the blue-green algae bloom in South Florida that has made national news?

No. Red Tide is a saltwater species, while blue-green algae is found only in freshwater. However, both are considered toxic.

When did this Red Tide start?

Last November. That makes it the longest lasting Red Tide this decade. The longest on record lasted for 17 months between 2004 and 2006.

What ends a Red Tide?

No one knows. Sometimes a tropical storm will blow through and dissipate the bloom or at least push it away from shore. However, the latest forecast shows slightly fewer storms and hurricanes this year than normal.

Is Red Tide a recent phenomenon?

No. Spanish explorers documented seeing it back in the 1500s. However, it remained poorly understood until a scientist named Karen Steidinger of the Florida Fish and Wildlife Research Institute in St. Petersburg spent decades putting it under her microscope. In tribute, scientists renamed the species to honor her, changing Gymnodinium breve to Karenia brevis.

Do humans have a role in starting a Red Tide bloom?

That's still unknown. Nobody knows what lights the fuse that ignites a Red Tide explosion. But scientists studying climate change say the rising temperature of the seas is likely to fuel even more harmful algae blooms like Red Tide. And when the Red Tide moves close to shore, it can be prolonged by nitrate pollution that flows into the waterways from overfertilized yards and leaky septic and sewage systems.

What does Red Tide do to wildlife?

Kills a lot of it. Work crews all up and down the coast have been going out on the beaches every morning and scooping up thousands and thousands of dead fish. Most, according to Jonathan Veach of the Florida Fish and Wildlife Research Institute, were baitfish and sportfish — snook and snapper, for instance. However some goliath grouper have died and one whale shark washed ashore last month, too, though scientists are still trying to determine the cause of the shark's death. Fish populations generally bounce back after a Red Tide, but the toxic bloom is also wreaking havoc among more sensitive animals. As of this week the bloom had been blamed for killing 452 sea turtles, all of them either endangered or threatened species, and about 92 manatees, also a threatened species. Between Aug. 7 and Aug. 9, Mote Marine Laboratory in Sarasota recovered the bodies of nine bottlenose dolphin that were also apparently killed by Red Tide toxins, according to Mote spokeswoman Hayley Rutger.

Does Red Tide affect humans too?

Yes, although not with such finality. The latest state report shows people at beaches from Sarasota to Naples reporting breathing problems as a result of encountering the Red Tide bloom. Usually the toxins cause only mild irritation and coughing, but they can produce serious problems for people with asthma and other respiratory problems. Health officials advise against eating shellfish from Red Tide areas because the toxins can accumulate in their bodies, poisoning humans.

Is it OK to eat seafood right now?

Most seafood restaurants aren't serving fish and crustaceans that were caught locally, so you'll be fine. If you want to eat a fish you caught yourself, be careful. Make sure it's alive when you reel it in. Only eat the muscle tissue of the fish, nothing else.

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Can I go swimming in the Red Tide?

If you can get past all the coughing and wheezing and dead fish floating in the water, sure! Most people don't develop the skin irritation that bothers a few who swim through the algae bloom. However, you should be sure to shower off thoroughly when you're done.

Can I still take my dog for a walk on the beach?

Yes, but don't let Fido play with any dead fish or foam on the beach, and give him a thorough rinse with freshwater when he's done — before he gets in your car, not after.

Should we find a way to destroy all algae in the ocean so we can avoid having this happen again?

No. Most blooms are beneficial because the tiny plants serve as food for animals in the ocean. They are the major source of energy in the ocean food web.

Information from the Florida Fish and Wildlife Conservation Commission, National Oceanic and Atmospheric Administration and Mote Marine Laboratory was used in this report. Contact Craig Pittman at Follow @craigtimes.