Summer heat brings algae blooms on the Big O

LAKE OKEECHOBEE — As the water in Lake Okeechobee heats up, algae and cyanobacteria blooms on the big lake become more common. Algae and cyanobacteria (sometimes called blue-green algae) are part of the lake’s natural ecosystem. Algae and cyanobacteria are the base of the food chain and produce much of the oxygen on the planet.

These microscopic organisms are always present in freshwater, unless the water is sterile. Much of the time they are not visible to the human eye. Under certain conditions, cyanobacteria can reproduce rapidly into what is called a visible “bloom.”

According to the U.S. Geological Survey data, 28 species of cyanobacteria have been documented in the Lake Okeechobee Waterway, which includes the St. Lucie River, the St. Lucie Canal, Lake Okeechobee and the Caloosahatchee River. About 25% of these cyanobacteria species are capable of producing toxins. Even those that are capable of producing toxins, do not always do so.

At the May 14 meeting of the South Florida Water Management District Governing Board, SFWMD Water Resources Division Director Lawrence Glenn said not only has SFWMD increased water sampling sites for this summer, but they are also sampling more frequently. SFWMD now has 30 sites in the lake that are sampled twice a month. The sites were placed strategically in areas where blooms have been seen in the past.

So far cyanobacteria blooms on the lake are pretty similar to last year, he said.

In April there were some blooms occurring along the eastern edge, he said. “Whenever our crews are out, if they seem a bloom they will collect a sample.” He said if the public sees a bloom they can report it to Florida Department of Environmental Protection (FDEP) and FDEP will sample and test the bloom.

In the May 6 sampling, he said eight of 30 sites detected cyanobacteria present. Seven of the eight sites contained microcystin ranging from barely detectable levels of less than 1 microgram per liter to a high of 35 micrograms per liter. The Environmental Protection Agency (EPA) has set 8 micrograms per liter as the safe level for human recreational contact.

Sometimes if there is a lot of wind, a larger drift congregates in an area, and that results in higher microcystin levels, he explained.

“We are still trying to learn about why and when toxins are released,” Mr. Glenn explained.

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