Local health officials lifted the red tide advisory on Wednesday that had been in place for some Sarasota County beaches since last week. 

Samples taken in mid-October last week showed low levels of Karenia brevis – the algae species that causes Florida red tide – present at several locations along the Sarasota County shore, according to the Florida Fish and Wildlife Conservation Commission.

The Florida Department of Health’s Sarasota County office posted signs at several south and mid-county beaches to notify members about the harmful algae's presence.

Previous coverage:After Hurricane Ian, could a red tide bloom in Sarasota spoil the holidays?

And:Health officials warn of elevated red tide levels at beaches in parts of Sarasota County

Health officials received testing results on Oct. 26 that showed no cells of Karenia brevis, the algae that causes red tide, were present. 

The beaches where warnings were posted included Turtle Beach, Nokomis Beach, North Jetty, Venice Beach, Service Club Park, Venice Fishing Pier, Brohard Beach and Caspersen Beach. The advisory signs have been changed at all of the beaches except for North Jetty, because of a temporary road closure associated with Hurricane Ian clean-up. The signs there will be changed as soon as possible, according to DOH-Sarasota. 

Results for Sarasota County beaches will be posted on Wednesday at ourgulfenvironment.net.

In an interview last week, Oceanography Professor Emeritus Robert Weisberg said that red tide typically forms offshore at about 90 to 120 feet of depth. As ocean current circulation begins to change in the fall, it carries Karenia brevis cells toward Florida’s Gulf Coast. This year, Ian seems to have helped stir the gulf just enough to push red tide to Sarasota, Weisberg said. 

“Conditions offshore have been conducive for red tide, what has been lacking is the ability to move red tide to the coastline and that changed with Ian,” he said. 

"Then, of course, there was a lot of runoff from the land that added further nutrient supply to what may already be a red tide offshore."

Herald-Tribune reporter Jesse Mendoza contributed to this report.

Anne Snabes covers city and county government for the Herald-Tribune. You can contact her at asnabes@gannett.com and follow her on Twitter at @a_snabes.