The proliferations have become increasingly common in recent years and can have health and economic impacts in affected areas ...

Red tide is caused by a harmful algae bloom. It can bring respiratory problems and even fish kills in high concentrations.

Fish kills can start when levels reach 10,000 cells per liter. In 20 Florida locations, concentrations were higher than 100,000. Health alerts for red tide have been issued in Lee, Collier counties.