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Tracking a Toxic Blue-Green Algae Bloom

July 25, 2023
water sample with algae

Scientists at the SCCF Marine Laboratory recently developed an experiment to sample a toxic blue-green algae bloom as it moved from freshwater, to brackish, to saline waters in the Caloosahatchee Estuary. 

Along with partners from the University of Florida (UF) and the South Florida Water Management District, the team targeted a visible blue-green algae bloom that formed near Fort Myers around July 17.

people sampling algae on boat

Water samples revealed the bloom as the toxic species Microcystis aeruginosa, which is known to form in nutrient-rich freshwater. It was predicted to move downstream toward Shell Point over a one- to two-week period based on regional bloom transport models previously developed by researchers on the team. 

“The bloom likely formed due to warmer temperatures and freshwater conditions typical this time of year,” said SCCF Marine Lab Director Eric Milbrandt, PhD.  

blue-green algae

Additional water samples on July 20 and July 24 confirmed that the bloom was at or near where it was projected to be. Samples were also taken to a microscopy lab at UF to determine patterns in the shapes of the colonies as the bloom progressed downstream.

“Our goal is to understand how the progression of the bloom impacts water conditions in the estuary over time through the production of toxins and release of toxins and nutrients into the water column,” Milbrandt said. 

The SCCF Marine Lab and UF have been sampling microscopic algae in the Caloosahatchee since 2018. On the first week of every month, they collect water samples from Lake Okeechobee, the Caloosahatchee from the Franklin Lock to Shell Point, and the Gulf of Mexico.

“Our results are identifying the drivers of seasonal phytoplankton blooms throughout the system,” Milbrandt said. 


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