What's turning Southwest Florida's shores brown? It's not red tide

The sand was white, but the murky, brownish water at some beaches in Collier and southern Lee counties continued to keep some would-be swimmers at bay Monday.

Discolored water has been reported at multiple locations, including Barefoot Beach, Seagate Beach and the Naples Pier, according to Naples' Natural Resources Manager Stephanie Molloy. Beachgoers on social media also reported a similar discoloration at Bonita Beach on Sunday.

But while red tide spells have ravaged Southwest Florida beaches and sea life for months, the discoloration is being caused by a bloom of a nontoxic diatom, called Cylindrotheca, Molloy said.

"There's lots of different species," she said. "When the conditions are right, they bloom."

But unlike red tide, which can cause respiratory issues and coughing for beachgoers, the diatom does not produce a toxin, Molloy said.