As the summer heats up, the Florida Department of Environmental Protection is tracking algae blooms all over the state.
The Florida Department of Health advises the public to stay out of water where algal blooms are visible. Without a laboratory test, you can't tell if what species of algae are in the water and you can't tell if toxins are present.
Cyanobacteria, commonly called blue-green algae, are part of the natural ecosystem of all lakes, streams and rivers. These microscopic organisms are believed to be the oldest life forms on the planet. Most of the time the cyanobacteria are invisible to the human eye, but under certain conditions they can reproduce rapidly into a visible “bloom.” Hot weather, lack of water movement and available nutrients in the water (phosphorus and nitrogen) make conditions ripe for harmful algal blooms (HABs).
Some species of blue-green algae are “nitrogen-fixers” and can use nitrogen from the air. Others, like the Microcystis aeruginosa commonly found in Lake O, cannot “fix” nitrogen and can only thrive if there is sufficient nitrogen in the water. Studies have found for algae that are not nitrogen-fixers, higher toxins levels are often found in areas with higher levels of nitrogen in the water.
The Environmental Protection Agency (EPA) considers microcystin levels below 1.0 parts per billion (ppb) to be safe for drinking water, and levels below 8.0 ppb to be safe for human recreational contact. At a meeting of the Florida Blue-Green Algae Task Force, officials explained “human recreational contact” includes swimming, and that warnings are based on the safe level for small children to be in the water -- they assume children may swallow some water while swimming.
May 22-25. FDEP collected samples from 14 sites statewide. Most sites had no toxins. Others had toxin levels below that is safe for drinking water. The sample from Bonita Lake had trace levels of toxins at 0.23 parts per billion (ppb). The sample from the Caloosahatchee River at Fort Myers Shores had 0.11 ppb. The Louise Lake sample at 0.36 ppb. A sample from the Pahokee Marina at 0.61 ppb.
May 22-24, South Florida Water Management District collected five samples from areas where algal blooms were reported.
• C43 canal (Caloosahatchee River) S77 (Julian Keen Jr. Lock at Moore Haven), upstream: Microcystis aeruginosa; trace level (0.40 ppb) microcystins detected.
• C43 Canal (Caloosahatchee River) S78 (Ortona Lock), upstream: Microcystis aeruginosa; 1.8 ppb microcystins detected.
• C23 Canal S48: No dominant algal taxon; no cyanotoxins detected.
• Lake Okeechobee - S354 (Miami Canal), lakeside: Microcystis aeruginosa; estimated 1.1 ppb microcystins detected.
• Lake Okeechobee - S352 (Canal Point spillway), lakeside: Microcystis aeruginosa; no cyanotoxins detected.
National Oceanic and Atomospheric Administration satellite imagery
In addition to the samples taken in response to reports of algal blooms, SFWMD samples 32 sites on Lake Okeechobee twice a month during the summer and once a month during the cooler months of the year.
The week of May 15-17, SFWMD collected 32 routine samples on Lake Okeechobee and three algal bloom response samples. Of the 35 sites sampled, eight sites had trace levels of toxins, three sites had low levels of microcystin toxins (above the level for drinking water but below the level considered safe for human recreational contact); one site had toxin levels above the level for human recreational contact; the rest had no toxins detected.
• The C44 canal (aka St. Lucie Canal) had no dominant algal for samples taken at the Port Mayaca Lock (canal side) or at Port Mayaca Post (lakeside).
• The C43 canal (Caloosahatchee river) upstream of the Julian Keen Jr. Lock at Moore Haven sample was dominated by Microcystis aeruginosa and had no cyanotoxins detected.
• The S-252 spillway at Canal Point samples had no dominant algal taxon.
• C51 Canal (in Palm Beach County) upstream samples had no dominant algal taxon and no cyanotoxins detected.
According to the U.S. Geological Survey, 28 species of cyanobacteria have been documented in the Lake Okeechobee Waterway, which includes the Caloosahatchee River, Lake Okeechobee, the St. Lucie Canal and the St. Lucie River. About 25% of these species are capable of producing toxins, but even those that can produce toxins do not always do so.
The following Lake Okeechobee stations were dominated by Microcystis aeruginosa and had toxins detected. Toxin results follow each station name:
• L004 (trace level, 0.56 ppb);
The following Lake Okeechobee stations were dominated by Microcystis aeruginosa but had no cyanotoxins detected: L008, L005, POLESOUT2, POLESOUT1, NES135, NCENTER, PELBAY3, L006 and PALMOUT1.
The following Lake Okeechobee stations had no dominant algal taxon or cyanotoxins detected: KISSR0.0, LZ2, NES191, EASTSHORE, POLE3S and LZ25A.