Sarasota, Florida (News-Press) -- If conditions remain favorable, a massive red tide bloom in the northeast Gulf of Mexico will eventually reach Southwest Florida.
But that's a very big if.
"It would take a while to get here," said red tide expert Kellie Dixon, a senior scientist at Mote Marine Laboratory. "In the past, when we've had blooms, if we get a big blow, it gets dispersed, so we might never see this one. If it hangs together and we get calm weather, the current will likely bring it south."
Red tide is a natural phenomenon caused by the single-cell alga Karenia brevis, which produces a powerful neurotoxin called brevetoxin.
When Karenia is in normal concentrations, fewer than 1,000 cells per liter of water, it's not a problem. But for reasons not well understood, Karenia sometimes undergoes a population explosion, or bloom, and the increased brevetoxin renders shellfish toxic to humans and can kill fish, birds, sea turtles and marine mammals.
FAQ: What is red tide?
The Florida Fish and Wildlife Conservation Commission announced the presence of the bloom July 25; it is now about 40 miles off Hernando and Pasco counties and measures 80 miles long and up to 50 miles wide.
Fish start dying when Karenia concentrations are 10,000 to 100,000 cells per liter of water; the latest counts were 900,000.
"We've seen higher counts, and the red tide event you had last year wasn't as high." Dixon said. "It's complicated by the fact that Karenia can swim, so you can have counts of 1 million per liter, then they glom together, and the next day you have 10 million."
FWC has received reports of thousands of dead marine animals from species including snappers and groupers, hogfish, grunts, crabs, flounder, bull sharks, baitfish, tomtates, filefish, octopus and triggerfish.
Researchers from Mote, FWC and the University of South Florida are monitoring the bloom this week aboard the 81-foot research vessel Bellows.
Among the researchers' tools are two underwater robots:
- Mote's robot, named Waldo, carries an optical phytoplankton discriminator, also known as a BreveBuster, which detects Karenia in the water. Waldo also measures water temperature and salinity, which helps scientists develop short-term forecasts of bloom movement.
- USF's robot, named Bass, collects data about chlorophyll as well as temperature, salinity and water density, which are used to predict currents.
Since being deployed Aug. 1, Waldo has found Karenia to depths of 80 feet, and Bass has found chlorophyll, which is associated with red tide, to depths of 130 feet.
Currents in the area are moving generally to the south, Dixon said.
"The bottom water is moving southeast, and the surface water is fairly stationary," she said. "It's moving southeast, but it's not moving anywhere fast."
Which means the currents are moving toward Southwest Florida, and the marine forecast through Friday for the northeast Gulf calls for westerly winds topping out at 10 knots, hardly the kind of blow that would disperse a major red tide bloom.
So it's a question of whether the bloom now in the northeast Gulf breaks up or hangs together.