Thick, red tide algae is no longer choking the shorelines of Manasota Beach and Gasparilla Island. But don't think it's gone just yet.
Nora Lea Reefe, president of the Boca Grande Garden Club, is one of the unfortunates most acutely affected by red tide.
"People tell me they think the red tide is gone because there is no west wind and they are not bothered by the mere presence up to 100,000 spores, but they may get a reaction when the wind blows," Reefe e-mailed from her second home in North Carolina where she is waiting out this year's red tide. "I have to remind myself to remember that the spores are there at a dangerous level for me regardless of whether the wind is blowing."
Mote Marine Laboratory scientists process water samples collected from the red tide bloom off Southwest Florida’s coast — an important step in a study about how red tide algae and other marine algae respond to nutrients in the water. From left: intern Alyssa Cartozian, and Kate Nierenberg, Mote senior biologist.
Tides strengthened from Hurricane Sandy loosened the red tide's grip around Gasparilla Island but wind gusts can still send it wafting back. Mote Marine Laboratory scientists are studying samples from the bloom in Southwest Florida while trying to find out how the nutrients come together to make this complex, nasty red tide soup recipe.
Since 2007, Mote has conducted 11 bioassays to learn how microscopic algae respond to nutrients. These field studies involve collecting water samples from Southwest Florida, including Boca Grande Pass, containing many varieties of microalgae, and then growing those algae in containers "spiked" with combinations of nutrients. Researchers also grow algae in containers with water from estuaries, where nutrients can be washed from land to the sea.
Mote scientists collected water samples from the bloom by boat Oct. 23. On Oct. 29, they collected water samples from three estuaries - Tampa Bay, Charlotte Harbor and the outlet of the Caloosahatchee River - areas that normally have more nutrients than the offshore waters where the bloom developed. They added estuarine water to bloom samples, left some samples alone and spiked other samples with specific nutrient combinations.
Analyzing all the samples and assembling the data in a comprehensive evaluation could take up to six months.
"We want to know how red tide algae respond to nitrogen, phosphorous, silica and other substances found along our coast, and learn how other types of algae might compete with or affect the red tide organism," said Gary Kirkpatrick, Mote Phytoplankton Ecology Program manager.
Results have shown that algae other than K. brevis usually dominate competitions for nutrients, and these algae show different responses to nutrients depending on the time of year and other factors - but algae were especially likely to grow and proliferate with added nitrogen.
Florida red tide, an intense concentration of alga Karenia brevis, occurs naturally in the Gulf of Mexico. Microscopic plant-like organisms, or phytoplankton, produce brevetoxins that kill fish and other marine life and cause respiratory illness among humans. No to mention stinking to high heavens.
Red tides usually begin 10 to 40 miles offshore become noticeable when carried near the coast by winds and currents.
Mote scientists have worked for decades to understand how Florida red tides develop, change and dissipate, but it remains a mystery different with each bloom. Mote scientists say a major complication is microscopic algae can compete against K. brevis for nutrients (food).
Nutrients can come from natural or manmade sources.
Red tide blooms offshore might start as nutrients released from sediments carried by ocean circulation patterns rise from the bottom.
Red tide blooms carried to shore strengthen when nutrients flow off the land, including plant and animal materials and fertilizers.
Until now, the bioassays contained too few red tide cells for scientists to learn much from their growth. The current bloom has allowed Mote scientists to add ae critical missing piece.
"This is an opportunity to use a moderate natural bloom of red tide algae and look closely at the response to added nutrients and combinations of nutrients," said Kellie Dixon, Mote Chemical and Physical Ecology Program manager. "We have already made some interesting discoveries about the algal community in general, and these findings have provided important context for understanding red tide, but the real keystone of this project is using a naturally occurring Karenia brevis bloom directly - and including the other algae that are present in the bloom and appear to compete for nutrients with K. brevis."