Winter algae blooms reported in Florida waters

Over the past month, the Florida Department of Environmental Protection has investigated 17 reports of algae blooms in Florida.

While algae and cyanobacteria blooms are commonly seen in Florida lakes, ponds and waterways in the summer, the algae and cyanobacteria are always present and the right conditions can result in a “bloom” even in the winter.

Algae and cyanobacteria (sometimes called “blue green algae”) are microscopic organisms. Rapid reproduction of algae into a mass that is visible to the human eye is called a “bloom.” Warm weather, low salinity levels, lack of water movement and the availability of a food supply of phosphorus and nitrogen are the ideal conditions for algae to reproduce.

You can’t tell if toxins are present by looking at an algae bloom. Of the more than 20 species of cyanobacteria documented in the Lake Okeechobee waterway, about 25 percent of the species are capable of producing toxins, according to the U.S. Geological Survey. However, cyanobacteria that is capable of producing toxins does not always do so. Most blooms contain a mixture of algae and/or cyanobacteria. Laboratory tests are needed to determine what algae and/or cyanobacteria are present and whether or not toxins are present.

Florida Department of Environmental Regulation has documented 17 algae bloom reports in Florida over the past 30 days, including five reports of algae in Lake Okeechobee and three algae blooms in the Caloosahatchee River and estuary. None of the Lake Okeechobee samples contained toxins, according to FDEP. Two of the Caloosahatchee River samples contained low levels of toxins.

An algae bloom on Cypress Lake in Orange County has the highest level of toxins, at 28 micrograms per liter.

In 2019, the Environmental Protection Agency set the safe recreational contact level for microcystin toxins at 8 micrograms per liter. The previous standard for recreational contact by humans, set by the World Health Organization was 10 micrograms per liter.

The most recent National Oceanographic and Atmospheric Administration (NOAA) image indicates “low to moderate algae potential” in 10 percent of Lake Okeechobee. The NOAA satellite images are produced with a computer program, based on light frequencies. The satellite looks at the amount of light in many wavelengths. To detect cyanobacteria, they use several wavelengths of red and near-infrared light (this infrared detects brightness, not temperature). The NOAA computer program does not indicate what type of blue-green algae or present or if any toxins are present.

Algae blooms reported in the past 30 days in the Okeechobee Waterway (which is made up of the Caloosahatchee River, Lake Okeechobee, the St. Lucie Canal and the St. Lucie River) included:
• Dec. 11, algae observed at Clewiston Boat Ramp. Dominant taxons were Microcystis aeruginosa and Cylindrospermopsis raciborskii. No toxins were detected.
• Dec. 11, algae observed near E. Cochran’s Pass on Lake Okeechobee in Glades County. Tests found dominant taxon was Microcystis aeruginosa. No toxins were detected.
• Dec. 11, algae observed on Lake Okeechobee, north of Clewiston. Testing found Microcystis aeruginosa and Cylindrospermopsis raciborskii were dominant in the sample. No toxins were detected.
• Dec. 16, algae observed on surface of water upstream of the Moore Haven lock on Lake Okeechobee in Glades County. Dominant taxon was Cylindrospermopsis raciborskii. No toxins were detected.
• Dec. 16, algae observed on the Caloosahatchee River upstream of the Franklin Lock. Tests found mixed algae. No toxins detected.
• Jan. 7, algae observed at the Franklin Locks on the Caloosahatchee River. Co-dominant taxa were: Microcystis aeruginosa and Cylindrospermopsis raciborskii. Low levels of toxins were detected at 0.63 micrograms per liter.
• Jan. 7, an algae bloom was reported at the Davis Boat Ramp in Lee County. Co-dominant taxa were: Microcystis aeruginosa and Cylindrospermopsis raciborskii. Tests found microcystin toxins at barely detectable levels of 0.48 micrograms per liter.

Publisher/Editor Katrina Elsken can be reached at

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