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HAB Research Reveals Phytoplankton Shifts

September 27, 2023
HAB Sampling

Researchers from the SCCF Marine Lab and the University of Florida have completed the second year of a 3-year study funded by the EPA and the U.S. Army Corps of Engineers to monitor and model harmful algal bloom (HAB) events in the Caloosahatchee. Results show phytoplankton shifts and correlations with dissolved organic nitrogen.

“Our sampling showed that dominant types of phytoplankton differ in freshwater versus the more marine parts of the system,” said Marine Lab Director Eric Milbrandt, Ph.D. “The freshwater sites were dominated by cyanobacteria and chlorophytes, while the marine sites around the Sanibel Causeway were mostly dinoflagellates.”

A new species of dinoflagellate found in freshwater was discovered in the samples.

Sampling also indicated a new species of freshwater dinoflagellate. Samples from the middle estuary by the Cape Coral Bridge were dominated by diatoms.

“The nearly 2-year sampling effort also revealed that productivity within the system was linked to watershed flows during the summer months,” said Milbrandt.

Dissolved organic nitrogen correlated with productivity within the system while inorganic nutrients were used up during the warm summer months.

Also of note, Hurricane Ian brought an unusually large amount of terrestrial runoff into the system, raising nutrient concentrations for several months. The harmful algal blooms occurring during this time were a freshwater blue-green algae bloom in July 2023 and a red tide bloom in the Gulf of Mexico from October 2022 to March 2022. Analyses of the bloom events are ongoing.


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