COLLIER COUNTY (CBSMiami) -- Red tide is making its way back to Southwest Florida waters.
The latest test results for Collier County show red tide is present at four of the five test sites.
Water samples taken earlier this week show the Florida red tide organism, Karenia brevis, was detected at medium concentrations at Barefoot Beach and Vanderbilt Beach which can also be seen in this real-time water quality map.
Low concentrations were found at Seagate Beach and the Naples Pier. Only South Marco Beach did not have red tide present.
Medium concentrations of red tide can lead to respiratory irritation and make fish kills "probable," according to the Florida Fish and Wildlife Conservation Commission. Low concentrations also can lead to respiratory irritation and "possible" fish kills.
Collier County officials are warning residents and visitors with respiratory problems to stay away from the water until conditions improve.
There are dead fish being reported "intermittently" from Barefoot Beach to Gordon Pass. Dead fish are also being reported in back bays, including the Cocohatchee estuary, Moorings Bay, Clam Bay and Naples Bay, according to the county.
In Lee County, a low-density patch of red tide has been lingering off Sanibel for a week or so.
The county is testing the water again on Thursday and results should be in by Friday.
Florida's red tide, which plagued the Sunshine state's coastline for 15 months in 2018, is one of the five worst toxic algae events in the state's recorded history, according to experts.
The 15-month long bloom caused respiratory irritations in people and killed vast numbers of sea turtles, manatees, dolphins and fish.
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