ENGLEWOOD — The Gulf waters of Stump Pass Beach State Park and Englewood Beach appeared clear of the impacts of the toxic red tide algae Thursday.

But that wasn’t the case on Don Pedro Island and portions of Lemon Bay, according to reports from Don Pedro Island resident Ken Conner and Manasota Key resident Bill Dunson, a retired Penn State biology professor.

Then the wind changed directions.

“It’s much better today,” Conner said Friday, crediting a southeast wind that blew the scent of red tide and any more dead fish up on the beach. “There must have been at least 100 vultures cleaning up the beach today.”

Conflicting reports did not surprise Alina Corcoran, a Florida Fish and Wildlife Conservation Commission researcher overseeing the state’s harmful algal bloom program.

On Dec. 28, the Florida Department of Environmental Protection tested water on Lemon Bay at Stump Pass and discovered moderate concentrations of red tide in the bay. Again, on Dec. 31, DEP water samples revealed high concentrations of red tide in the Gulf at Stump Pass.

According to the latest report posted on the FWC website Friday, a bloom of red tide algae — Karenia brevis — spanned coastal waters of Southwest Florida between southern Sarasota and Monroe counties. The highest concentrations were detected alongshore of Charlotte and Lee counties, including Pine Island Sound.

Researchers deem the natural background presence of red tide as levels of 1,000 cells or fewer per liter of water. Very low counts are more than 1,000 cells to fewer than 5,000 cells per liter. Red tide can cause fish kills and respiratory irritations when concentrations exceed 100,000 cells or more of the algae concentrated in a liter of water.

The blooms generally first blossom 11 to 45 miles offshore, but researchers haven’t identified what first triggers them. According to researchers, winds and currents drive red tide ashore. Toxins generally are released when the delicate algal cells break up due to wave action.

In October, a red tide bloom plagued Gulf shorelines from Tampa Bay south to Collier County, but that bloom was blown south into the Florida Keys.

“I hate to speculate, but this may be a new bloom,” Corcoran said, adding that this latest outbreak has remained patchy.

According to FWC historical data, while red tide outbreaks are seen in the fall months, Corcoran said it is not unusual to see outbreaks in the winter months. The wind direction — out of the west or northwest — blows the algae close to shore, she said.

The public is encouraged to report red tide or any other fish kills to the FWC hotline at 800-636-0511. Call 866-300-9399 to hear recorded reports of red tide throughout the state, or go to www.myfwc.com/research/redtide.

Email: reilly@sun-herald.com