The beaches in Siesta Key, Fla. periodically experience red tide, a condition that occurs when high levels of red-tinted and harmful algae are present in the water. During red tides, the ocean water may display a reddish-brown hue.
Red tide is caused by high concentrations of the microscopic alga Karenia brevis. It can be dangerous to people with respiratory conditions and may cause an increase in dead fish on beaches. The Mote Marine Laboratory and Aquarium in nearby Sarasota, Fla., provides twice-daily updates on the red tide conditions of nearby beaches, including those at Siesta Key. The Mote Marine Laboratory also releases a twice-weekly report forecasting red tide conditions.