Red tide spreads out, lingers along coast

A strong patch of red tide that was on Sanibel just days ago has spread out in the Gulf of Mexico but in less dense, less deadly concentrations. 

Red tide (Karenia brevis) occurs naturally in Southwest Florida waters and can cause fish, marine mammal and sea turtle kills as well as respiratory issues in humans. 

"The high numbers were right along the beaches, and now the water there looks a lot clearer," said Rick Bartleson, a water quality scientist at the Sanibel-Captiva Conservation Foundation on Sanibel. "What was at the beach has moved away and has kind of spread out. The wind had been pretty strong so that may have taken a patch of red tide that was affecting the beaches. It may have taken it away for a while."

Red tide exploding off Lee beaches

Strong east winds have blown for about a week now, and those winds seem to be keeping the red tide offshore and causing it to disburse. 

The National Weather Service is calling for those east winds to remain in place over the next week.  

The Florida Fish and Wildlife Conservation Commission released a report Friday that showed low to medium levels along the Lee and Charlotte county coasts. 

Red tide is measured in cells per liter, and last week more than 100 million cells per liter were counted along Sanibel beaches. That concentration is dense enough to be seen from outer space. 

Collier County waters tested clean of toxic levels, according to FWC reports.

Lingering red tide leads to more fish kills, manatee injuries

Coastal  birds, mostly cormorants, have been treated for red tide poisoning at the Center for the Rehabilitation of Wildlife, or CROW, on Sanibel in recent weeks. 

Those birds are often the canary in the coal mine for forecasting as the birds eat fish that have accumulated the toxin. The poison continues to build up in the birds as they continue to eat fish, and sick birds end up with neurological issues. 

A University of South Florida forecast shows the red tide patches offshore over the next few days. 

Bartleson said most of samples he collected in Lee County waters were positive for red tide. Higher concentrations, as high as 400,000 cells per liter, were found inside Blind Pass. 

Lingering red tide leads to more fish kills, manatee injuries

"We still have less than 50,000 (cells per liter) at most of the sites that we looked at but we haven't seen any high-mediums or highs (counts)," Bartleson said. 

Levels are considered high when they reach 1 million cells per liter, which is as high as the FWC report counts. 

FWC's most recent reports show red tide off Lee and Charlotte county beaches but not in other counties along the west coast. 

Tracy Fanara, with Mote Marine Laboratory in Sarasoat, told The News-Press recently that  beachgoers will get a tickle in their throat and develop a cough if exposed to high levels of the neurotoxin. 

Red tide bloom intensifies off SWFL

"Some people are really sensitive and others aren’t," Fanara said. "It almost feels like it’s very dry air that’s forcing you to cough. It’s a very strange sensation. It’s almost like an allergic reaction. Some people get itchy eyes and runny noses and uncontrollable coughing."

Red tide typically starts in October and can be fed by nutrients from Lake Okeechobee and from the Caloosahatchee River watershed — which is all the lands to the north and south of the river that drain into it. 

"We’re not seeing any dead fish and we’re not hearing much about people having coughs," Bartleson said. "But when I went to Blind Pass I could feel it there when we were sampling, but it doesn’t take a lot for me to feel it." 

Connect with this reporter: Chad Gillis on Twitter. 

Red tide

Red Tide (Karenia brevis) in cells per liter:

0 to 1,000: background levels with no impact anticipated

1,000 to 10,000: possible respiratory irritation, shellfish harvesting closures

10,000 to 100,000: Respiratory issues, possible fish kills and bloom chlorophyll likely detectable by satellites at upper limits

100,000 to 1,000,000: All the above plus discoloration of water

Source: Florida Fish and Wildlife Conservation Commission