Resilience Natural Disasters

Toxic red tide returns to Florida

Fish killed by a red tide in Florida

Story at a glance

  • Florida declared a state of emergency last year during a 16-month red tide that killed untold tons of fish and nearly 150 dolphins.
  • Now red tide is back, and residents are worried they may again find their beaches covered in stinking piles of rotting sea life for months to come.

A red tide is once again sweeping up Florida’s west coast, killing marine life and giving residents respiratory problems.

Though red tides are nearly an annual occurrence in the Sunshine State, many Floridians have dreaded the resurgence of the toxic microorganisms responsible for the red tide. 

That’s because beginning in the summer of 2017, a red tide turned the state’s beaches into a putrid horror show for 16 straight months. Across 145 miles of coastline, the once pristine sands were strewn with the washed up corpses of fish, sea turtles, dolphins and manatees that had succumbed to the toxins. 

The red tide, caused by blooms of a dinoflagellate called Karenia brevis, finally let up around Feb. 2019, but now the Florida Fish and Wildlife Conservation Commission is once again detecting elevated levels of Karenia brevis along the state’s west coast, CNN reports

Residents who lived through the last red tide are worried about the impacts of another protracted bloom on public health, wildlife and local economies. 

Following last year’s 16-month disaster, Gov. Ron DeSantis formed a Red Tide Task Force to study the causes of red tides and potential solutions.

So far, the current outbreak has remained relatively mild, with elevated levels of Karenia brevis detected near Sarasota, Lee, Collier and Charlotte counties. Fish kills have been reported in the areas with the highest concentrations. 

What sets off a specific red tide is often hard for scientists to pinpoint, but humans may be making the conditions that allow them to thrive more common. Florida’s plentiful agricultural runoff is loaded with nutrients in the form of chemical fertilizers, which could prolong and exacerbate red tides once they get going. Large pulses of runoff may also increase as tropical storms get bigger and wetter due to climate change. 

Whether climate change plays a more direct role is hard to pin down, as Karenia brevis thrives in warm water but falters once temperatures exceed 83 degrees Fahrenheit. However, some research has suggested that as humans pump more carbon dioxide into the atmosphere and warm the planet, the microorganism may be able to proliferate in even warmer waters.