Red tide questions surface at Siesta gathering

From September through April, people living along the coast in Sarasota County dealt with a protracted red tide bloom.

Beyond the usual issues associated with red tide — conditions that can lead to respiratory ailments and the death of marine life — residents took note of what seemed like an unusually long period of high concentrations of Karenia brevis algae.

At the May 5 Siesta Key Association meeting, Mote Marine Laboratory and Aquarium volunteer and Siesta Key resident Tommy Vaughan-Birch explained the history of red tide and the conditions in which the algae can thrive. She addressed residents’ most pressing question about the phenomenon: Are humans making it worse?

The answer is complicated, Vaughan-Birch said. The algae itself is not man-made. The blooms originate 10 to 40 miles offshore, and red tide can be traced back 10,000 years.

But the red tide needs certain conditions to remain in the water. Vaughan-Birch said nutrient availability and water temperature are key factors in triggering a red tide bloom, with the organism preferring warmer conditions. Those at the SKA meeting wondered if run-off into the coastal waters — including discharge from the Siesta Key wastewater treatment facility during Hurricane Hermine in September — is exacerbating the red tide blooms.