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The toxic algae bloom may be linked to clouds of iron-rich dust from the Sahara Desert.
By Times staff and wire reports
© St. Petersburg Times, published August 30, 2001
FORT MYERS -- Thousands of fish are dead, killed by a swath of Red Tide just offshore along southwest Florida's gulf coast, and officials are waiting to see where the toxic algae bloom drifts next.
Experts at the Florida Marine Research Institute expect it to head south and not threaten the Tampa Bay area.
Dead fish began washing ashore last weekend on North Captiva Island in Lee County near Fort Myers. But managers at parks south of there reported that they had so far found no fish kills or any of the other telltale signs of Red Tide: the stench of dead fish and odors from the bloom that cause coughing fits and itchy eyes for beachgoers.
The fish kills that have occurred so far have been patchy, not concentrated in one area, according to Scott Willis, a spokesman for the Florida Marine Research Institute in St. Petersburg.
Although it is impossible to predict exactly where the Red Tide might go next, indications at this point are that it will head south, he said.
The single-cell algae that causes Red Tide blooms is always present in gulf waters, usually at low concentrations. But occasionally something triggers a massive bloom, typically between September and February.
No one knows for sure what triggers the blooms, but University of South Florida researchers said Wednesday it may be clouds of iron-rich dust from the Sahara Desert that blow thousands of miles across the Atlantic Ocean.
A study used satellites and ground monitoring stations to track a Saharan dust cloud in 1999 to a region between Tampa and Fort Myers, where a huge bloom of Red Tide then erupted.
The scientists think iron in the dust causes the algae, normally present in small quantities, to grow into large concentrations that kill fish, make shellfish toxic and create respiratory problems for humans.
"We're still trying to figure out if all this is true, and if it is true then we can predict it," said John J. Walsh, a USF marine science professor who co-authored the study.
The study appears in the September issue of the scientific journal Limnology and Oceanography.
The Sahara emitted another dust cloud this year that may be to blame for the Red Tide again blooming of North Captiva. But the USF researchers have not taken iron measurements this year.
Meanwhile, wildlife managers in the vicinity of the bloom were keeping a close watch.
"Red Tide is always a concern for us," said Kevin Godsea, a ranger at the J.N. "Ding" Darling National Wildlife Refuge on Sanibel Island. "We're all keeping an eye out for it."
Terri Behling, a spokeswoman for Mote Marine Laboratory in Sarasota, said the bloom apparently started forming two weeks ago, 5 miles offshore. A week ago, the bloom was off the island of Boca Grande. Since then, it has drifted 20 miles south to North Captiva.
Once the bloom reaches 10,000 organisms per liter of water, Red Tide becomes toxic to slow-moving, bottom-dwelling fish and shellfish.
While this bloom might keep heading south, it might not harm people or fish if its toxicity level drops.
"If it continues to come further south and stays organized, I'm going to grab a water sample and see if it's at the toxic level," said Jim Locascio, a marine biologist at the Sanibel-Captiva Conservation Commission.
-- The Associated Press and staff writer Craig Pittman contributed to this report.