While Gulf waters off Manasota Key and elsewhere in Charlotte and Sarasota counties remain red tide free, Lee and Collier counties’ waters continue to carry toxic with red tide algae.
The toxic blooms, however, may be creeping up the coast, and some algae has been found in samples in lower Charlotte Harbor.
Throughout Lee and Collier counties and for several weeks, the Florida Fish and Game Conservation Commission collected water samples that turned up medium concentrations of red tide — 100,000 to 1 million cells per liter of water — and high concentrations of more than a million cells.
The higher concentrations had been limited to Pine Island Sound south to Marco Island. Charlotte and Sarasota counties had experienced natural background counts of the algae or very low counts, less than 10,000 cells per liter of water.
In the last eight days, background concentrations rose to low concentrations in two water samples, one taken from Boca Grande Pass, which is in Lee County, and a second in Gasparilla Sound, south of the Cape Haze peninsula in Charlotte Harbor, just inside the Charlotte County line.
One of those samples, the one taken in Boca Grande Pass, dropped from “low” to “very low” when the state updated its map Wednesday.
State scientists release updates at myfwc.com.
Reports of red tide blooms date back to the Spanish Conquistadors.
While naturally present in the Gulf, medium to high concentrations can cause coughing and other respiratory ailments in humans. Respiratory ailments have been reported due to the latest blooms in Lee and Collier counties. The toxins are often released when winds and waves break up the cells.
Intense red tide blooms are also known to kill fish and other marine life, including marine mammals.
From Dec. 31 to Jan. 7, the FWC received reports of 16 fish kills in Lee County and another 22 in Collier County due to the red tide. There were no fish kill reports in Charlotte or Sarasota counties.
The wildlife commission describes intense red tide blooms as forming “as a result of the interactions between biology, chemistry, and ocean currents that unite nutrients with light and carry red tide to the beach.”
The algae initially propagates in the Gulf of Mexico 10 to 40 miles offshore, miles from any human impacts, and then can be transported towards shore by winds and currents.
While there is no direct link between nutrient pollution and the frequency or initiation of red tide blooms, research has shown once red tides are transported inshore, the algae is capable of feasting on man-made nutrients for their growth.
Blooms of higher-than-normal concentrations of the red tide algae occur annually in the Gulf of Mexico, according to the wildlife commission.
Southwest Florida saw a horrific, highly intense and long-lasting red tide blooms throughout 2018. Toxic blooms maimed the local economy and left hundreds, if not thousands, of fish and other marine life, including dolphins and manatees, dead and washed up onto shores.
Even so, it wasn’t a first.
“The years 1946-1947 saw a horrendous fish kill here on the West Coast,” local historian Diana Harris wrote in a Sun column in 2016.
That historic red tide bloom resulted in fish kills extending from the Florida Keys to Tarpon Springs, north of Clearwater. The bloom was estimated to be about 40 miles wide and reportedly killed millions of fish.