Scientists develop measuring stick for Florida’s Red Tides

The people of Florida’s Gulf Coast know (and hate) a bad Red Tide when they see one.

Between coughing and sneezing at the beach and dead fish littering the sand, the signs are hard to miss. But until now, scientists say, they have never had a true measuring stick for comparing blooms from year to year.

“The question might be, ‘How bad was it?’ ” said Richard Stumpf, a National Oceanic and Atmospheric Administration oceanographer who studies harmful algal blooms. “We can quantify that now.”

Although Red Tides have plagued Florida for centuries, most efforts to forecast and understand them are relatively new. Stumpf is one of eight researchers behind a recent study establishing 0-to-10 scales (10 being most extensive) for measuring past blooms — one focusing on how far they reached and how long they lasted, and another accounting for how much breathing trouble they caused people onshore.

The authors hope it’s a step toward a system that could assign ratings to Red Tides in real time, like how meteorologists categorize the potential danger of hurricanes by wind speed.

Scientist Barbara Kirkpatrick, a study co-author and member of Florida’s Harmful Algal Bloom/Red Tide Task Force, said people tend to think each Red Tide is the same. But the research shows every bloom is unique, and toxic algae can be patchy — intense in one place while nonexistent several miles down the coast.

“One of the things it does is dispel people’s worry that all blooms go from St. Pete to Naples and out 50 miles,” she said. Just like the difference between a Category 1 hurricane and a Category 5, Kirkpatrick said, Red Tides “are highly variable.”

Having a better grasp of the severity of individual blooms should help local governments prepare, Kirkpatrick said, similar to how they respond when a storm approaches. For instance, officials could more confidently estimate how much debris and dead fish they will have to pick up. Florida has suffered devastating Red Tides twice in recent years, including from 2017 to 2019 and last summer.

In both cases, Pinellas County reported picking up more than 1,800 tons of dead sea life and debris. But those blooms differed in location and timing, with the latest Red Tide hitting earlier and farther up Tampa Bay.

To develop the measurement systems, researchers reviewed Red Tide water sampling data from 1953 to 2019, as well as reports of respiratory irritation in Manatee and Sarasota Counties from 2006 to 2019.

Before the mid-’90s, sampling was scattershot, often performed in response to fish kills or reports of breathing difficulty. Interest in Red Tide was dependent on the weather, Stumpf said, because wind has a major impact on how much people suffer from the toxic algae.

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.

Loading...

You’re all signed up!

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

Explore all your options

When a breeze blows onshore, it carries Red Tide toxins released into the air over waterfront neighborhoods and beaches. But a wind blowing offshore takes those toxins out to sea. Dead fish work the same way. Winds blow snook, seatrout, pinfish and other carcasses either onto the coastline or out to the Gulf of Mexico. People might not even know about a significant Red Tide nearby, depending on the day.

Since 1994, the study’s authors found, some of Florida’s worst Red Tides hit around 2006, 2012 and 2018.

Kirkpatrick, a senior adviser for the Gulf of Mexico Coastal Ocean Observing System, said the periodic nature of algae blooms has made it hard for scientists to secure funding in the past. Research grants oscillated with public interest based on conditions in any given year. But she said the government has recently started to offer more consistent support.

Moving forward, Stumpf said he hopes to update the research annually based on the latest Red Tide. Florida is not currently experiencing a bloom. Red Tide usually picks up in the fall.

The algae almost always make an appearance, though. From 1994 to 2019, the researchers said, only once — in 2010 — did the southwest coast (roughly from Collier to Pasco counties) escape a bloom entirely.