A toxic algal bloom known as a red tide has continued to plague parts of Florida’s southwest coast over the past week, resulting in fish kills and respiratory irritation.
The red tide has persisted since October, when high levels of algae reached the coast shortly after Hurricane Ian stirred the Gulf of Mexico.
“By killing the fish, it generates its own supply of nutrients”, Robert Weisberg, professor emeritus of oceanography at the University of South Florida, said in October, when the bloom was just beginning to appear on the radar. “Once he’s done that, he’s on the go and it’s very hard to stop him.”
As to what causes a bloom to dissipate, scientists still don’t have a solid answer. However, historical patterns have confirmed a typical pattern for flowers, according Cynthia Heil, director of the Red Tide Institute at Mote Marine Laboratory in Sarasota: A red tide typically begins in late summer or fall, lasts five to seven months, and ends in the spring.
As the densest part of the current bloom has drifted north in recent days, algae levels have declined somewhat around Sarasota County, but reports of dead fish and respiratory irritation continue to arrive. county public beaches, including Siesta Key. The bloom’s presence is also stronger around Anna Maria Island and Tampa Bay, according to water samples and local reports.
It also wraps around the southern end of Pinellas County, where impacts have already started hitting some beaches.
In Manatee County, fish kills and respiratory irritation were reported at Anna Maria, Holmes Beach and Bradenton Beach this week. Water samples taken by the Florida Fish and Wildlife Conservation Commission and its partners last week confirmed the presence of the red tide.
Wildlife officials determine the severity of algae by measuring the number of algae cells. Karenia brevis — the microscopic organism that causes red tide — present in a liter of water. At medium and higher levels, the algae is considered to have reached full bloom strength and is more likely to cause adverse effects to human health and the environment.
In Manatee County waters, medium concentrations of red tide were detected Monday at the Rod and Reel Pier in Anna Maria and northeast of the island. Low levels were found near Longboat Pass to the south and the Sunshine Skyway Bridge to the north. High levels were found to the northwest and much farther offshore near the mouth of Lower Tampa Bay.
In total, a red tide has been detected in 76 water samples off Hillsborough, Pinellas, Manatee, Sarasota, Charlotte, Lee and Collier counties over the past week, FWC said in an update.
Red tide impacts sensitive habitat in Sarasota Bay
The red tide does more than pollute the beach conditions on the gulf side of the barrier islands. Algae can also accumulate in the Intracoastal Waterway, where it has the potential to concentrate in shallow waters and damage sensitive marine habitats.
The current red tide bloom has persisted at high levels in the intracoastal waters of Sarasota Bay for several weeks. The bay, which borders Sarasota and Manatee counties, has already been hit hard by red tide in recent years. Scientists largely blame the blooms for wiping out decades of seagrass recovery there.
As an estuary, Sarasota Bay and its seagrass beds and oyster beds play an important role as a haven for manatees, dolphins, game fish and countless other marine life, according to the Sarasota Bay Estuary Program.
“80 to 90 percent of Florida’s commercially valuable fish and shellfish species spend part of their lives in an estuary,” SBEP said. bay field guide said.
Although red tides occur naturally, a growing body of evidence suggests that human pollution can fuel blooms and make them worse once they approach the coast.
The ongoing impacts of climate change on natural phenomena, including more intense hurricanes, changes in rainfall amounts and warmer water temperatures, also have the potential to promote harmful algal blooms, according to the Environmental Protection Agency.
Locally, water quality advocates emphasize the importance people can have in curbing algal blooms by reducing sources of pollution in area waters; these sources include sewage spills, leaking septic tanks, pet waste that isn’t picked up, and overuse of lawn fertilizer.
Changes in our infrastructure and our habits could alleviate some of the pressure on already endangered water bodies, they say.
Restore water health
During a virtual water quality roundtable on Monday, local government officials and scientists weighed in on the state of local waterways, including the role of red tide.
The intensity of the current red tide bloom is likely the result of polluted runoff after Hurricane Ian, said Sarasota Bay Estuary Program Manager Dave Tomasko — a mix of natural forces unpredictable and preventable human pollution.
The Estuary Program and its partners found high levels of bacteria, algae and nutrients in the bay in the weeks after Ian.
Tidal exchanges between Sarasota Bay and the Gulf of Mexico gradually lowered levels, Tomasko said. But there was a downside.
“We pushed a lot of these nutrients into the Gulf of Mexico,” Tomasko said. “Sarasota Bay improving from tidal exchanges likely contributed to a larger red tide than it would have been without the effects of Hurricane Ian.”
Now the water quality balance in the bay is again disturbed by the red tide.
Despite the setbacks, Tomasko said restoring his health was within reach.
“We try to manage the berry by managing nutrient loads,” Tomasko said.
SBEP calculated that it would take a reduction in nutrient loading of around 20% to restore the waters to the much healthier levels seen between 2006 and 2012.
“We have more than enough to act on,” Tomasko said. “Spills and overflows, septic tanks, reclaimed water, storm water. If we do a lot of action on all these things, we will be able to return to the [nutrient] load we had when we were a healthier berry. And we are going to be able, we believe, to maintain the course of population growth over the next 30 years.
Red tide forecast
The The National Oceanic and Atmospheric Administration predicts the respiratory threat of the red tide. On Thursday, NOAA warned of a moderate to high risk of respiratory irritation on the coasts of Pinellas, Manatee and Sarasota.
Respiratory risk is more likely when winds blow on or along the shore.
A red tide forecast from the University of South Florida predicts low to medium levels of algae will persist around Anna Maria Island through the weekend. The highest concentrations are expected around the northern end of the island as well as in the Intracoastal and near the mouth of Palma Sola Bay.
Continued northward spread towards Pinellas County is expected, with low to high red tide levels around Fort De Soto Park, Shell Key Preserve and the southern tip of the county.
An uneven spread of very low to high levels of red tide is expected to continue along the Sarasota County coast.
Red Tide Safety Tips
The Florida Department of Health in Manatee County provides the following red tide safety tips:
- Look for information boards posted at most beaches.
- Stay away from water.
- Do not swim in waters with dead fish.
- People with chronic respiratory problems should be especially careful and stay away from these places as the red tide can affect your breathing.
- Do not harvest or eat distressed or dead shellfish or fish from these areas. If caught alive and healthy, finfish are safe to eat as long as they are filleted and the innards discarded. Rinse the fillets with tap or bottled water.
- Wash your skin and clothes with soap and fresh water if you have had recent contact with red tide.
- Keep pets and livestock away from water, sea foam and dead marine life. If your pet is swimming in red tide water, wash it as soon as possible.
- Residents living in beach areas are advised to close windows and run the air conditioner, ensuring the A/C filter is maintained to manufacturer specifications.
- If outdoors near an impacted location, residents may choose to wear masks, especially if onshore winds are blowing.
This story was originally published December 12, 2022 10:30 a.m.