MANATEE -- A large patch of red tide off Sarasota and Charlotte counties is moving north, causing fish kills over the past couple of days, scientists said.
A couple of samples taken in Tampa Bay showed low concentrations of the red tide organism, said Alina Corcoran, research scientist for the Florida Fish and Wildlife Conservation Commission in St. Petersburg.
However, the biggest patch is off Sarasota County, and as evident on satellite images, it is moving north, said Corcoran.
"In Sarasota County, we are seeing medium concentrations there," she said, adding that there are reports of "a rather massive redfish kill."
Red tide blooms result when the water temperature and salinity reach a certain point for growth of algae, she said.
In enough concentration, red tide can cause respiratory distress, which people have reported in both Sarasota County and around Anna Maria Island, she said.
Asked whether she expected the red tide bloom to migrate to Manatee County's shores, she said, "It has been moving north pretty quickly."
"We'll have more information tomorrow, once samples are processed," Corcoran said Wednesday.
A weather front expected today and Friday is accompanied by a "very strong wind field," that may drive the surface bloom south, said Jason Lenes, a research associate for the Center for Prediction of Red Tides at the University of South Florida College of Marine Science.
"We are starting to feel some slight issues with red tide," said Manatee County Public Safety Capt. Joe Westerman, adding that he's heard a few minor complaints of respiratory irritation at Manatee Beach.
He said the big bloom off Sarasota County is "pretty widespread, a pretty big swath of it offshore."
"My hope is there's a cold front coming through that could push it southward," Westerman said.
He confirmed some fish kills at Longboat Key and at Siesta Key, in Sarasota.
There are just a few fish starting to float at Coquina Beach, he said.
Sara Kennedy, Herald reporter, can be reached at 941-745-7031. Follow her on Twitter@sarawrites.com.