Tampa Bay has Red Tide questions. Here are some answers.

It’s here. It’s not new. It’s deadly to fish and unpleasant to the rest of us. Here’s what you need to know about the Red Tide crisis.
Published July 17, 2021|Updated July 29, 2021

For centuries, it has plagued Florida’s Gulf Coast. Now it has returned to Tampa Bay to afflict everything it touches:

The ecosystem, the economy, people’s livelihoods and their health, and especially the waters of the bay itself as it kills hundreds of tons of sea life.

But what is Red Tide anyway? Why does it thrive here? And when will this current outbreak let up?

You have questions. The Tampa Bay Times has answers — though there is still much that scientists say they have yet to learn.

Check out some key sources here: The Florida Fish and Wildlife Conservation Commission’s Red Tide page and Mote Marine Laboratory & Aquarium.

Related: Amid Red Tide, Tampa Bay’s snook, redfish and trout fishing restricted again
• • •

What is Red Tide?

Red Tide is a collection of harmful algae. Here we are specifically referring to a tiny marine organism called Karenia brevis.

It is a microorganism that produces neurotoxins and can be found in the Gulf of Mexico all the time but usually at levels low enough that it doesn’t cause significant harm.

• • •

What is a bloom?

A Red Tide bloom develops when Karenia brevis is found at higher-than-normal concentrations.

Related: Tampa Bay waterfront restaurants take a hit from Red Tide
• • •

Why is Red Tide plaguing Tampa Bay now?

Much of the bay is beset by elevated levels of Red Tide. High concentrations have been reported as far north as Hillsborough Bay. Bloom levels are also being detected along Pinellas County’s prized gulf beaches. The state takes water samples to detect those concentrations and posts the results online.

• • •

Where did this come from? Does the Piney Point disaster have anything to do with it?

The harmful algae feast upon nutrients regularly found in Tampa Bay, such as nitrogen.

Keep up with Tampa Bay’s top headlines

Keep up with Tampa Bay’s top headlines

Subscribe to our free DayStarter newsletter

We’ll deliver the latest news and information you need to know every morning.

You’re all signed up!

Want more of our free, weekly newsletters in your inbox? Let’s get started.

Explore all your options

Excess nitrogen enters the water in many ways, including through fertilizer runoff and wastewater released from land.

But this year, scientists say, the Red Tide is almost certainly finding more fuel because of a singular manmade catastrophe: More than 200 million gallons of polluted water was dumped into the bay between late March and early April off the grounds of the old Piney Point fertilizer plant in Manatee County.

The state allowed the release by property owner HRK Holdings because regulators feared a large, leaking reservoir was about to collapse, sending a devastating flood into surrounding neighborhoods and businesses. That wastewater was dumped into the bay at Port Manatee and carried a lot of nitrogen with it.

Related: Failure at Piney Point: Florida let environmental risk fester despite warnings
Dead fish in the water at Vinoy Park.
Dead fish in the water at Vinoy Park. [ ARIELLE BADER | Times ]

You may have heard local leaders and researchers repeat over and over again that Piney Point did not cause this Red Tide.

What they mean is: The release is not why Karenia brevis turned up in the bay. That doesn’t mean the pollution couldn’t be exacerbating the bloom.

Think of a brush fire: Something has to give off a spark, like a match, to get it going. The flames then need dry material to keep burning. In this case, nutrients — those already in the bay and the enormous amount added by Piney Point — are the fuel.

As for the ignition? Scientists have theorized that several environmental factors may be at play. Among them:

Persistent southerly winds likely blew a Red Tide bloom that began in Southwest Florida late last year north, eventually hitting Tampa Bay. On top of that, scientists have said, drought-conditions and a lack of freshwater here left the estuary with high salinity levels that are conducive to Karenia brevis.

Related: Could Tampa Bay’s Red Tide be connected to Piney Point disaster?
• • •

Why is it killing so much marine life?

City employees work to remove a dead goliath grouper from the waters off Crisp Park.
City employees work to remove a dead goliath grouper from the waters off Crisp Park. [ ARIELLE BADER | Times ]

Red Tide is toxic. Karenia brevis specifically produces brevetoxins, which kill fish and can lead to the deaths of other marine animals. According to the Florida Fish and Wildlife Conservation Commission, neurotoxins released in a bloom “affect the central nervous system of fish and other vertebrates.”

Related: Red Tide is killing fish. Are Tampa Bay’s birds in danger?

Death comes for fish, the agency said, when “their gills stop functioning.” Birds like cormorants and pelicans may be afflicted when they eat food contaminated with toxic chemicals. Other animals up the food chain can get exposed the same way.

Bad Red Tide outbreaks have been known to prompt die-offs of turtles, dolphins and manatees. More than 1,800 tons of dead sea life was removed from Pinellas’ shores during the 2017-19 outbreak.

• • •

When will the bloom go away?

For now, experts say there is no immediate relief on the horizon. But Red Tide is in many ways still a mystery, and scientists don’t know what ends a bloom, said Bob Weisberg, a physical oceanography professor at the University of South Florida.

And no, humans cannot kill the Red Tide on their own.

Related: No Red Tide relief in sight as dead fish overwhelm St. Petersburg

The state Fish and Wildlife Conservation Commission says a bloom “can last as little as a few weeks or longer than a year.

“They can even subside and then reoccur,” the agency says. “The duration of a bloom in nearshore Florida waters depends on physical and biological conditions that influence its growth and persistence, including sunlight, nutrients and salinity, as well as the speed and direction of wind and water currents.”

• • •

How long has Red Tide been a problem for Florida?

Quite a while.

Florida’s wildlife agency says Red Tides were noted in the gulf in the 1700s and “fish kills near Tampa Bay were even mentioned in the records of Spanish explorers.”

Related: Red Tide, stench of dead fish hangs over Fort De Soto beaches
Dallas Ard, 27, of Holiday, and Clayton Gilbert, 29, of Orlando, walk by a fish kill by the St. Pete Pier.
Dallas Ard, 27, of Holiday, and Clayton Gilbert, 29, of Orlando, walk by a fish kill by the St. Pete Pier. [ ARIELLE BADER | Times ]
• • •

What role do humans play in a bloom?

Pollution puts nutrients into the water that Karenia brevis can use as food, according to Mote Marine Laboratory & Aquarium.

The state explains that scientists have not directly linked nutrient dumping to the start of Red Tides or how frequently they occur, but once blooms drift inshore, “they are capable of using manmade nutrients for their growth.”

Related: Along St. Petersburg’s waterfront, the park is quiet but the smell is strong

“Red Tides occurred in Florida long before human settlement, and severe Red Tides were observed in the mid-1900s before the state’s coastlines were heavily developed,” the Fish and Wildlife Conservation Commission writes. “No single factor causes blooms of K. brevis. Blooms form as a result of the interactions between biology, chemistry and ocean currents that unite nutrients with light and carry Red Tide to the beach.”

• • •

Does Red Tide affect people, too?

A pile of dead fish was gathered on the bow of boat in June when Pinellas County collected dead fish in Dunedin and around Clearwater Harbor.
A pile of dead fish was gathered on the bow of boat in June when Pinellas County collected dead fish in Dunedin and around Clearwater Harbor. [ CHRIS URSO | Times ]

It can. Waves “can break open K. brevis cells and release these toxins into the air,” according to the state. People may suffer minor problems breathing. Those with chronic respiratory conditions could experience more severe effects. Beachgoers sometimes feel an itchy throat, watery eyes and irritated nose when they’re around Red Tide.

Related: A touristy Tampa Bay dolphin tour through dead fish, Red Tide

Studies have shown an association between blooms and higher rates of emergency room visits or hospital admissions for respiratory, neurological and digestive symptoms. Experts recommend wearing a mask when exposed to Red Tide, particularly the immunocompromised.

Those who live in affected areas should also avoid harvesting their own shellfish, which can accumulate toxins and sicken those who eat them.

• • •

Is it okay to eat seafood right now?

For the most part, yes. Most of what you buy at grocery stores and restaurants comes from offshore. Regulations are strict for seafood safety.

“This particular Red Tide is really restricted to the very near-shore area from north of Port Charlotte up to Pasco County, and in terms of sourcing traditional grouper, snapper, scallops … they wouldn’t be affected by this,” Steve Murawski, a professor of fishery biology at the University of South Florida’s College of Marine Science, told the Times.

Related: Is it safe to eat seafood in the Tampa Bay area during Red Tide?

Anglers and diners should, however, be cautious about seafood harvested around Tampa Bay where the current Red Tide is present. The state instructs residents not to eat “dead or distressed” fish but says it is okay to filet and wash other fish while throwing away the internal organs, where toxins build up.

• • •

Can I walk my dog on a beach with Red Tide?

The Florida Department of Health says: “Pets can become sick from Red Tide so keep them away from those areas.”

Definitely do not let your dog eat dead fish.

Related: St. Petersburg council to DeSantis: Declare Red Tide emergency
• • •

Can I swim in Red Tide?

No. You should not. The state health department advises that toxic chemicals “could cause skin irritation, rashes and burning and sore eyes.”

People spend time at Ben T. Davis Beach, where advisories warned beach-goers about Red Tide in late June.
People spend time at Ben T. Davis Beach, where advisories warned beach-goers about Red Tide in late June. [ MARTHA ASENCIO-RHINE | Times ]
• • •

Where is all the dead stuff going?

Pinellas County has said fish pulled from the water are typically burned at a waste to energy facility to make electricity. Carcasses washed ashore, and thus mixed in with sand and dirt from the ground, get landfilled.

• • •

What is the state doing about Red Tide?

Local officials and environmental groups have called on Gov. Ron DeSantis to declare a state of emergency. He has not. The governor’s office says there is no need to do so because the state has a dedicated funding source that the Department of Environmental Protection can tap to help local governments pay for the costs of dealing with the bloom.

Related: Environmentalists urge DeSantis to declare Red Tide emergency

“DEP began the process of executing an initial grant agreement with Pinellas County the week of June 21, 2021. As of July 16, 2021, the state has committed $2.1 million to Pinellas County to cover cleanup costs incurred for both Pinellas County and the City of St. Petersburg,” said agency spokeswoman Dee Ann Miller in a July 20 email to the Times. “DEP will continue to work with Pinellas County to provide funding as additional costs are incurred.”

The state is also working on a similar agreement with Hillsborough County, which has not seen nearly as many dead fish wash ashore as Pinellas. Agencies have also increased water sampling around Tampa Bay, Miller said.

• • •

This all stinks. What can I do?

You can report fish kills. In St. Petersburg, call the Mayor’s Action Center at 727-893-7111 or use St. Petersburg’s SeeClickFix website.

In Tampa Bay, call the Florida Fish and Wildlife Conservation Commission at 1-800-636-0511 or file a fish kill report online.

Beyond the present crisis, experts say, a good starting point is to work on own your little corner of the world.

Pinellas County Public Works Director Kelli Hammer Levy said people are understandably frustrated with the pollution from Piney Point — an environmental danger to Tampa Bay that the state never truly curbed.

But she recommended that they also focus on reducing their role in creating the pollution that ends up in Tampa Bay and the gulf, all of which stacks up.

For instance, she said, people can avoid letting grass clippings full of nutrients land in the water or they could buy fertilizers with fewer chemicals that ultimately run off into canals. They should stop overwatering their yards if they’re on reclaimed water.

Pet owners can pick up their dog’s waste, because if they don’t, that poop will get washed out through the drains, too.

“It’s part of our responsibility to do what we can to limit what ends up in the environment,” she said. “We can do better.”

Times staff writers Helen Freund and Rose Wong contributed to this report.

Editor’s note: This report was updated July 20 with a statement from the Department of Environmental Protection.

• • •

Red Tide resources

There are several online resources that can help residents stay informed and share information about Red Tide:

The Florida Fish and Wildlife Conservation Commission has a website that tracks where Red Tide is detected and how strong it is.

Florida Poison Control Centers have a toll-free 24/7 hotline to report illnesses, including from exposure to Red Tide: 1-800-222-1222

To report fish kills and get them cleaned up in Tampa Bay, call the Florida Fish and Wildlife Conservation Commission at 1-800-636-0511 or file a fish kill report online.

To report them in St. Petersburg, call the Mayor’s Action Center at 727-893-7111 or use St. Petersburg’s seeclickfix website.

Visit St. Pete/Clearwater, the county’s tourism wing, runs an online beach dashboard at

Pinellas County shares information with the Red Tide Respiratory Forecast tool that allows beachgoers to check for warnings.

• • •

How to stay safe near the water

  • Beachgoers should avoid swimming around dead fish.
  • Those with chronic respiratory problems should be particularly careful and “consider staying away” from places with a Red Tide bloom.
  • People should not harvest or eat mollusks or distressed and dead fish from the area. Fillets of healthy fish should be rinsed with clean water, and the guts thrown out.
  • Pet owners should keep their animals away from the water and from dead fish.
  • Residents living near the beach should close their windows and run air conditioners with proper filters.
  • Visitors to the beach can wear paper masks, especially if the wind is blowing in.

Source: Florida Department of Health in Pinellas County