Blue-Green Algae (Cyanobacteria)

Florida’s traveling public should refer to the Florida Department of Environmental Protection and Florida Department of Health for the most up to date information and safety guidance on algal blooms in Florida.

What are Blue-Green Algae?
Blue-green algae, or “cyanobacteria,” are natural to the environment’s food chain and are found all over the world.  They are actually a type of bacteria but, like plants, use sunlight to grow. Many live with other types of algae and microscopic animals, collectively termed “plankton.”

Where are Blue-Green Algae found?

Blue-green algae are found in marine waters, as well as freshwater and brackish habitats.  Under the right conditions, cyanobacteria can grow rapidly resulting in an algal bloom.  Environmental factors such as light, temperature and nutrients contribute to bloom formation.  An algae bloom may appear green, red, purple or rust-colored, sometimes resembling spilled paint.  A bloom may be found on the water surface, below the surface, or mixed throughout the water column.  Over time, these toxins are diluted and eventually break down and disappear. 

What causes Blue-Green Algal blooms?
Although blue-green algae can occur naturally, increases in nutrients can exacerbate the extent, duration and intensity of blooms.  Other facts that contribute to blooms include warm temperatures, reduced water flow and circulation, and lack of animals that eat algae.  Although they can occur at any time, blue-green algae are most common in Florida in the summer and early fall, with its high temperatures and abundant sunlight.  The summer also brings storms that have the potential to deliver nutrients into waterways through storm water runoff.  As algae in a cyanobacterial bloom die, the water may smell bad.

What are the health risks associated with Blue-Green Algal blooms?
Health risks associated with cyanobacteria occur when people or animals are exposed to toxins that are sometimes produced by these organisms.  Exposure can happen through unintentionally swallowing lake or river water, breathing water spray or coming into direct contact with the blooms.  At high levels, these can affect the gastrointestinal tract, liver, nervous system and skin.  It is not possible to tell if a bloom is toxic by looking at or smelling the water.  Therefore, it is recommended that people avoid contact with all algal blooms.  Children and pets are especially vulnerable, so keeping them away from the water during a bloom is especially important.

What should I do if I come in contact with Blue-Green Algae?

Blue-green algae toxins can affect the liver, nervous system and skin.  Abdominal cramps, nausea, diarrhea, and vomiting may occur if untreated water is swallowed.  Some people who are sensitive to the algae may develop a rash or respiratory irritation.  If you come into contact with an algae bloom, wash with soap and water right away.  If you experience an illness, please contact your healthcare provider immediately.

Can I eat fish harvested from areas near or in Blue-Green Algae blooms?

No. Do not eat fish that are harvested from areas near or in blooms.

Is it ok to use Blue-Green Algae water for showering or irrigation?

Untreated water from the bloom area should not be used for irrigation when people could come into contact with the spray.  Do not use untreated water from the area with the bloom for showering or bathing.

Who determines if a Blue-Green Algal bloom poses a risk to human health?

Some – not all – blue-green algae can produce toxins that can contribute to environmental problems and affect public health.  The Florida Department of Health (DOH) takes the lead in determining if an algal bloom presents a risk to human health.  DOH issues health advisories as they determine to be appropriate when toxicity levels are higher, and may also post warning signs when blooms affect public beaches or other areas where there is the risk of human exposure.  These actions are typically directed out of local county health departments, most often in consultation with staff from DOH’s Aquatic Toxins Program.  The World Health Organization considers levels under 10 micrograms/liter to represent a low-level risk for adverse health outcomes from short-term recreational exposures; however, certain sensitive populations (e.g., children, the elderly and immunocompromised populations) may still be at risk even at low concentrations and should avoid any exposure.  DOH also follows up on reports of pets that may have been exposed to a bloom, since these events may predict potential human health threats.

What is being done about the Blue-Green Algae blooms at the state level?
To ensure the health and safety of our state’s residents and visitors, the Florida Department of Environmental Protection (DEP) is committed to keeping Floridians updated on current algal blooms and how the state is responding to protect human health, water quality and the environment.  DEP, the five water management districts (WMDs), the Florida Department of Health (DOH), the Florida Fish and Wildlife Conservation Commission (FWC) and the Florida Department of Agriculture and Consumer Services (DACS) all work together to respond to algal blooms, each with a specific role. This “bloom response team” coordinates activities based upon the nature of the bloom event.

DEP and Florida’s WMDs frequently monitor Florida’s water quality, and routinely collect algal bloom samples as soon as they are observed as part of this effort.  In addition, staff can be deployed to take additional samples in response to reported blooms – whether from a citizen, other response team agencies or other sources.

The algal bloom response team takes all algal blooms seriously and all federal, state and local agencies will continue to respond as quickly and efficiently as possible to both observed and reported algal blooms to ensure the health and safety of Floridians, visitors and our natural resources. 

What agency should I contact to report a Blue-Green Algae bloom?

The state’s bloom response team encourages residents to report algal blooms so that they can respond quickly and effectively. To report a bloom, call the toll-free hotline at 855-305-3903 or click here to report online. To report human illness or for information on health advisories, contact your local county health department.  To report a fish kill, contact FWC’s Fish Kill Hotline at 800-636-0511 or click here to report online.