Satellite data shows rising threat of red tide for Florida Gulf Coast

TAMPA – Satellite data from off Florida’s Gulf Coast shows the reason for increasing concern about red tide, which can impact not only humans but also lead to widespread mortality events among marine animals.

Following Hurricane Milton’s landfall on Oct. 9 near Sarasota, satellites detected significant levels of chlorophyll, which can sometimes be a precursor to the production of red tide events. 

Chlorophyll fluorescence was greatest from southwest of Cedar Key through west-central Florida to around Venice—the area was also hardest hit by the Category 3 hurricane.

According to the U.S. Department of Energy’s Office of Science, powerful tropical cyclones lead to the vertical mixing of seawater, which can cause upticks in photosynthesis. 

This biological process produces blooms of algae, which can have both good and bad consequences, depending on the type of phytoplankton species involved.

“We have been keeping a close eye on this red tide that started before the two hurricanes, and we were not surprised to see its quick development after the hurricanes,” Chuanmin Hu, a professor of Oceanography at the University of South Florida, told FOX Weather.

Hurricanes can also contribute to red tide by producing increased runoff from land, causing fertilizers and other pollutants to enter the ocean. 

The influx of chemicals creates favorable conditions for red tide to flourish, sometimes spreading over large areas.

TOXIC ALGAE BLOOM BECOMING DEADLY FOR SEA LIONS, DOLPHINS PACIFIC OCEAN

Previous hurricanes led to significant red tide events

Large amounts of Karenia brevis, the microscopic algae that produce red tide, were also detected in the weeks and months after Hurricane Ian impacted Southwest Florida in 2022, and occurred for several years after Irma struck the coastline in 2017.

A massive red tide bloom along the Sunshine State’s coastline from late 2017 to 2019 killed hundreds of sea turtles, more than 200 manatees and a similar number of dolphins, according to a Mote Marine Laboratory and Aquarium report. 

In addition to marine impacts, humans can also suffer health effects caused by red tide, according to medical experts. 

The American Lung Association states that those exposed to the toxins can experience respiratory symptoms, which include coughing, sneezing, runny nose, wheezing or shortness of breath. 

In more severe cases, red tide has been linked to impairment of some cognitive abilities, for which the best remedies are known to be over-the-counter antihistamines.

FLORIDA PREPARES FOR INFLUX OF MANATEES SUFFERING FROM RED TIDE

Before the recent string of hurricanes, high levels of Karenia brevis were already being detected along some coastal communities around the Clearwater area, with experts fearing the organisms will continue to spread. 

Chuanmin said his group, along with the state’s Fish and Wildlife Research Institute, is especially concerned about the impacts on marine life and has been collecting water samples to determine the extent of the bloom. 

One of the species the Florida Fish and Wildlife Conservation Commission keeps a close eye on is the manatee.

The animal has been experiencing what is termed an Unusual Mortality Event, with prior occurrences of red tide contributing to the situation.

According to the FWC, between November 2022 and June 2023, at least 123 manatees died from the red tide bloom statewide. 

Wildlife biologists say that the giant sea cows can ingest the toxin by eating contaminated seagrass or inhale it from the air. 

Effects include seizures and weakness, making it difficult for the animals to breathe and swim. 

The agency estimates there are only around 7,500 manatees left in the Sunshine State, and if boaters see an animal in distress, they should inform the agency about the sighting by calling 888-404-3922.