February 10, 2017
Red tide lingering, aimed at Lee
By Chad Gillis
A red tide that’s lingered in the Gulf of Mexico for several months is expected to move toward Lee County over the weekend.
Recent counts from the Tampa Bay area south to Marco Island show concentrations ranging from background levels to high levels of Karenia brevis, the organism that causes red tide here.
“We have had high counts both inshore, alongshore and offshore,” said Kate Hubbard, a lead research scientist with the Florida Fish and Wildlife Conservation Commission, the state agency that tracks red tide. “The bloom itself has been fairly patchy, so we’re not seeing a solid patch that stretches (from Tampa Bay to the Marco Island area).”
Strong red tides can kill fish and marine mammals as well as cause respiratory irritation in humans.
Red tide occurs naturally and has been recorded for centuries in this region, although excess nutrients running off the Florida landscape can intensify or extend the life of a bloom.
Fish kills were reported in Lee County waters in November and December, although no fish kills had been reported in Lee or Collier counties in recent days.
“I had sort of stopped looking at samples because they were showing up zero, but one of our staff is testing now,” said Rick Bartleson, a water quality scientist at the Sanibel-Captiva Conservation Foundation. “I’m guessing with the tides and some of the cold fronts, it’s headed this way.”
A cold front moved through the area Friday, and cooler temperatures and high winds can dampen red tide growth, or break up the concentrations.
"The growth rate of the red tide slows down when the water is cooler, and also the wind can cause waves which damage the cells because they’re fragile," Bartleson said. "Also the wind can push the water around and dilute the red tide. Sometimes none of that happens."
Southwest Florida has seen highs in the 80s in recent weeks, with relatively calm winds and seas.
"Warm weather and still weather both promote the blooms, so the stiller water helps keep the blooms intact and the warm weather allows them to grow at a faster rate," Bartleson said.
Red tide typically hits the Sanibel-Captiva area first, before working its way further south to Bonita Springs, Naples and Marco Island.
"It’s low to moderate, and that pretty much is how it’s been in January and February," said James Evans, Sanibel's natural resources director. "But water clarity is good at the beach and the causeway."
Hubbard at FWC said most of the higher concentrations are well offshore at this time. The stronger concentrations that were found in Lee County were near the Collier County border about 16 miles offshore, Hubbard said.
"It’s still very dynamic and patchy," Hubbard said. "Over the next three days, we do expect there to be net southern movement of transport of the surface waters and the cells that are in those surface waters."