Blue-Green Algae

Blue-green algae, or cyanobacteria, occur frequently in Florida’s freshwater environments. Blue-green algae are microorganisms that function like plants in that they use light energy from the sun and nutrients acquired from the environment to help them grow.

Blooms occur when rapid growth of algae leads to an accumulation of individual cells that, in turn, discolor water, often produce floating mats that produce unpleasant odors, and may negatively impact fish and other aquatic animals.

Some environmental factors that contribute to blue-green algae blooms are sunny days, warm water temperatures, still water conditions and a plentiful supply of nutrients.

Reducing the supply of nutrients, nitrogen and phosphorus in particular, can help decrease the intensity and duration of blue-green algal blooms.

Blue-green algae blooms tend to form or develop in freshwater systems, whereas red tide often develops 10-40 miles offshore. While red tide may move into bays and estuaries, the algae that cause red tide cannot survive in freshwater waterbodies.

Whether algal bloom conditions are observed during routine sampling or in response to a citizen generated report, sampling teams enter the site visit information (location, bloom conditions observed and note whether toxins were detected) in real-time. This information is currently displayed on the statewide water quality map.

Statewide Water Quality Map

You cannot tell if blue-green algae are producing toxins just by looking at a bloom.

Don’t drink or swim in water where blue-green algae blooms are present; sensitive individuals (e.g., children, the elderly, and those who are immunocompromised) may still be at risk even at low concentrations and should avoid any exposure.

DEP tests algal samples to determine the type of algae present. If the algae are capable of producing toxins, the sample is subject to additional testing to determine if toxins are present in the water or not.

Recurring and persistent blooms are routinely monitored to assess whether a bloom is producing toxins.

The Florida Department of Health (DOH) takes the lead in determining if an algal bloom presents a risk to human health. When appropriate, DOH issues health alerts and may also post signs when blooms could affect people using beaches or other areas where there is a potential for exposure.

Many blue-green algae can produce toxins and algal blooms can result in high toxin concentrations. Exposure to blue-green algae blooms can cause health effects in people and animals. Most problems occur when water containing high amounts of algal toxins are ingested.

Direct contact or breathing airborne droplets containing high levels of algal toxins during swimming or showering can cause irritation of the skin, eyes, nose and throat.

Learn More

The state’s algal bloom response team encourages everyone to be on the lookout for algal blooms and report them. Blooms can be reported to DEP 24 hours a day, seven days a week online at ReportAlgalBloom.com or toll-free at 1-855-305-3903.

Report an Algal Bloom