Fear of red tide causing false alarms in southwest Florida

SARASOTA — Two months after wildlife officials declared Florida's red tide outbreak over, scientists have found traces of the toxic algae in three Southwest Florida counties, but it's a far cry from the red tide bloom that plagued the state for 18 months.

In a word, it's normal.

There is no red tide bloom.

There were very low concentrations found in single samples collected in Manatee, Charlotte and Lee counties, according to the Florida Fish and Wildlife Conservation Commission.

The re-emergence of even background levels of Karenia brevis on Friday's FWC red tide status report — and reports of respiratory irritation for the first time since February — led to public fears that another outbreak could be forming.

However, the anecdotal reports of breathing problems were attributed to other sources, not red tide, FWC said.

A non-harmful red drift, a woolly seaweed known as macro algae, washed up Tuesday on Sarasota County beaches.

"There has been an absence of red tide in the vast majority of samples collected over the past several weeks," FWC Research Institute spokeswoman Michelle Kerr said. "The report of background cell concentrations in Friday's status update is correct. We often see background Karenia brevis cell concentrations in the absence of a bloom, and at the same time, sometimes we will go several months without detecting any cells."

Karenia brevis is a single-celled plant-like organism that is carried to shore through environmental conditions such as wind and ocean currents. Scientists debate whether nutrient pollution, such as nitrogen and phosphorus, allows it to reproduce close to shore.

The toxic algae prefer warm and calm salt water. When the red tide cells die, they emit a brevetoxin that kills sea life, including 589 sea turtles during the last episode — the most in any single red tide event — along with 213 manatees and 153 bottlenose dolphins since July 2018.

Historically, a red tide outbreak disappears in the cool winter months, from December to March, but can develop from August to December. A bloom persisting past December can occur, especially when the average temperature is above normal, as it has been the past several months.

Temperatures in February were the second warmest on record in Sarasota.

Following one of the five worst red tide episodes in recorded history that destroyed generations of sea life from Pinellas County south 150 miles to Monroe County, Florida's Gulf waters are slowly healing. Coastal residents are still reporting brackish waters in many areas.

Kate Hubbard, an FWC scientist, says that those monitoring the red tide updates and the samples map, which is updated at 5 p.m. daily, should be aware that the threshold for a bloom is more than 100,000 Karenia brevis cells per liter.

"Background concentrations are when we see cells, but at concentrations of fewer than 1,000 cells per liter (our limit of detection is typically 333-500 cells per liter, based on the volume of seawater examined)," she said. "We are continuing to monitor coastal and estuarine waters statewide, engaging numerous partners and volunteers (including citizens).

"Also, as one example, FWC's harmful algal bloom scientists had a sampling trip that went 20 miles offshore of Tampa Bay yesterday (Monday); we conduct these monthly. Results are still pending but should be available later this week."

Robert Weisberg, a professor of physical oceanography modeling and a forecaster at the Collaboration for Prediction of Red Tides, says the center will make a seasonal prediction in early June based on what conditions are like in spring. The red tide prediction center is a joint project between the FWC Research Institute and USF's College of Marine Science.

The CPRT has predicted 21 out of the last 26 red tide episodes, including the most recent.

Beachgoers who are looking for daily beach reports can go to visitbeaches.org for updates on water color, algae, jellyfish, water temperature and rip currents, and more.

I have received no reports of respiratory irritation or dead fish and still we are not seeing anything greater than background concentrations of Karenia brevis.

The reports of RI was from the BCRS which I manage- one was a mistake, the other was due to odor unrelated to red tide

— Dr. Tracy Fanara (@inspectorplanet)March 30, 2019