Some toxic blooms unrelated to lake releases

OKEECHOBEE – The summer heat continues to contribute to conditions ripe for algal blooms in South Florida.

While the media has widely publicized the cyanobacteria (commonly called blue-green algae) concentrations in Lake Okeechobee, cyanobacteria blooms in waterways that do not receive any water from Lake Okeechobee have tested positive for toxins this summer.

On July 16, the Florida Department of Environmental Protection confirmed reports of blue-green algae in St. Lucie County on the C-25 canal near 25th Street. The C-25 canal has no connection to Lake Okeechobee. Samples of the surface bloom taken on July 9 indicated the dominant toxin is Microcystis wesenbergii. Microcystin toxin levels were low at 0.33 micrograms per liter.
According to the World Health Organization, microcystin levels of less than 10 micrograms per liter are safe for recreational contact.

Algae sampled in the North Fork of the St. Lucie River near Bessy Creek on July 2 was mixed algae with no dominant species. Total microcystin was low at 0.74 micrograms per liter. Microcystis aeruginosa was the dominant species in sample taken June 14 of an algal bloom in the North Fork of the river just north of Bessy Creek. While Microcystis aeruginosa is one of the species capable of producing toxins, no toxins were detected in that sample.

The lake bloom is large. The National Oceanic and Atmospheric Administration imagery shows cyanobacteria in the water column in 80 pecent of the lake. However, the concentration levels have decreased over the past two weeks according to NOAA. So far, tests from areas were algae is visible have shown no toxins or toxin levels of less than 10 micrograms per liter.

There have been no fish kills on Lake Okeechobee this summer.

As is normal in summer, nontoxic algae blooms have also been observed, off and on, in lakes, ponds, retention ponds, canals and waterways all over South Florida. According to the Florida Department of Environmental Protection, algae is part of the normal ecosystem in freshwater; it’s the base of the food chain.

Most algae and cyanobacteria does not produce toxins, and even cyanobacteria that can produce toxins does not always do so. You cannot tell if an algae bloom is toxic by looking at it, FDEP warns. The public is advised to avoid contact with water when there is a visible algae bloom.

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