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Cyanobacteria in Florida Surface Water Reservoirs

Cyanobacteria (or blue-green algae) are commonly found in Florida's lakes, rivers, and estuaries. Some species can produce toxins that affect public health and the environment.

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Cyanobacteria (or blue-green algae) are ubiquitous in Florida’s freshwater and brackish habitats (lakes, rivers, and estuaries). Like red tides, cyanobacteria can increase in concentration and can form visibly obvious blooms or “scums.” These blooms or scums can lead to a decrease in oxygen levels and contribute to fish kills. Some cyanobacteria are also known to produce toxins that can contribute to environmental problems and affect public health and natural resources.

In 1998, recognizing the need to assess the status of toxic microalgae in Florida, the state legislature approved funds to the Florida Harmful Algal Bloom Task Force (FLHABTF) to address any potential concerns regarding microalgae, including cyanobacteria. Collaborative studies funded by the FLHABTF were initiated between the St. Johns River Water Management District, the Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute, Florida Department of Health (DOH), private laboratories, and Wright State University to investigate the distribution of toxic cyanobacteria and their toxins (cyanotoxins) in Florida waters. A total of $700,000 was expended for cyanobacteria on monitoring, investigation, and a workshop on toxin detection and quantitation.

Several groups of toxic cyanobacteria have been detected in Florida’s aquatic systems. Among the groups, or genera, are Microcystis, Anabaena, and Cylindrospermopsis. While there is a potential concern that cyanobacterial toxins can enter into reservoir systems used for drinking water, there have been no documented cases of illnesses in Florida directly related to drinking water containing these toxins. In other states and countries, incidences of skin irritation, swollen lips, eye irritation and redness, earaches, skin itchiness, sore throats, hay fever-like symptoms, or fatigue have been reported after swimming in highly affected lakes. In Florida, there have been no illnesses reported from recreational activities in lakes directly related to cyanobacteria blooms, based on information from the Florida Department of Health.

Although the U.S. Environmental Protection Agency (EPA) has not set guidelines for safe limits of cyanotoxins in drinking water systems in the United States, the EPA has been requested to do so. Microcystins, anatoxin-a, and cylindrospermopsin occur in Florida freshwater systems and surface waters used for drinking water. Recently, there has been international concern that a newly described neurotoxin could lead to neurodegenerative disease if ingested via drinking water. The toxin, known as beta-N-methylamino-L-alanine (BMAA), is produced by some blue-green algae. Water treatment plants can effectively treat for microcystins because there are off-taste and odor problems at the time of blooms. Additionally, the water is treated with activated charcoal, which also removes the most common toxins. Other detection and treatment methods are possible. A workshop in 2001 supported by FLHABTF funds discussed alternatives and needs (Cyanotoxin Detection and Quantification and Instrumentation Workshop [CDQIW], PDF 1.1MB).

More information on cyanobacteria blooms, their toxins, and public health effects can be found in the Proceedings of Health Effects of Exposure to Toxic Cyanobacteria Toxins: State of the Science, August 13–14, 2002 (DOH Division of Environmental Health). To report any illness that you may have resulting from cyanobacteria exposure, call the Marine and Freshwater Toxin Hotline at 1-888-232-8635. This number connects to the Florida Poison Information Center in Miami, which has contracted with DOH to receive such reports. The number should be answered by a person who will document the caller's observations and experience.

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