LAKE OKEECHOBEE – Hot temperatures continue to encourage algal blooms in Lake Okeechobee. Algae and cyanobacteria (also known as blue-green algae) are naturally present in all lakes, streams and ponds. Algae are the base of the food chain and an important part of the ecosystem. Much of the time, algae — which is always there — are not visible to the human eye. When levels of phosphorus and nitrogen are high, the weather heats up and there is little water movement, conditions are ripe for algae to reproduce rapidly into visible “blooms.”

According to the U.S. Geological Survey, there are 28 different species of cyanobacteria in the Lake Okeechobee Waterway, which includes the St. Lucie River, the St. Lucie (or C-44) Canal, Lake Okeechobee and the Caloosahatchee River. About a quarter of cyanobacteria species are capable of producing cyanotoxins. Even those capable of producing toxins do not always do so.

Throughout the year, the Florida Department of Environmental Protection (FDEP) and the South Florida Water Management District (SFWMD) sample Florida lakes and rivers for algae and test for toxins. During the summer, they sample more frequently.

They also use the National Oceanic and Atmospheric Administration (NOAA) satellite imagery to monitor bloom “potential.” The computer-generated imagery uses satellite images to predict the probability of an algal bloom in a given area. The areas in red or orange have the highest probability of surface scum. Cyanobacteria cannot move on their own — they are pushed about by the water currents and wind — but cyanobacteria can rise and fall in the water column by inflating and deflating gas vesicles.

Last week, two samples from Lake Okeechobee contained cyanobacteria, but no microcystins were detected.

For the week of Aug. 14-20, NOAA imagery for the lake showed bloom “potential” in about 50% of the lake. The highest potential was observed along the northeast and northwest shores. The most recent images show this bloom potential has decreased.

Two samples taken from Lake Okeechobee last week contained cyanobacteria.

On Aug. 17, South Florida Water Management District staff collected samples from Lake Okeechobee at FEBOUT (in the Glades County portion of the lake, about 4 miles offshore, just south of Brighton Seminole Reservation) of and FEBIN (also in Glades County’s area of the lake, about 5 miles west of FEBOUT station and about 2 miles offshore). The FEBOUT sample was dominated by Planktolyngbya limnetica, while the FEBIN sample was dominated by Cylindrospermopsis raciborskii. Microcystins were not detected in either sample; however, a trace level (0.29 parts per billion) of cylindrospermopsin was detected in the FEBOUT sample.

FDEP also samples other lakes and rivers around the state, and responds to reports of algal blooms.

On Aug. 13, samples taken of an algal bloom in Cape Coral had microcystin level of 3 micrograms per liter.

The Environmental Protection Agency (EPA) considers microcystin levels above 8 micrograms per liter to be unsafe for human recreational contact (such as swimming) and levels above 1 microgram per liter to be unsafe for drinking water.

FDEP advises: Different types of blue-green algal bloom species can look different and have different impacts. However, regardless of species, many types of blue-green algae can produce toxins that can make you or your pets sick if swallowed or possibly cause skin and/or eye irritation due to contact. FDEP advises the public to stay out of water where algae is visibly present as specks, mats or water is discolored pea-green, blue-green or brownish-red. Additionally, pets or livestock should not come into contact with the algal bloom-impacted water, or the algal bloom material or fish on the shoreline.