Frequently Asked Questions
What is 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, they can use sunlight to grow. Many live with other types of algae and microscopic animals, collectively termed “plankton.”
- Blue-green algae are a group of organisms that are among the oldest on the planet. They are ubiquitous - found in marine waters as well as freshwater and brackish habitats. Blue-green algae are also common in other states, including Georgia, Texas, Alabama and Michigan.
- Some – not all – blue-green algae can produce toxins that can contribute to environmental problems and affect public health. Those blue-green algae that are known to produce toxins do not always do so. Little is known about exactly what environmental conditions trigger toxin production.
- Blooms can float on the surface and be several inches thick or they can lie below the surface of the water. Blooms can disappear from view or move to different parts of a pond or lake.
What causes blue-green algae blooms?
- Blue-green algae multiply quickly in water bodies with
high nutrient levels such as phosphorous or nitrogen, and
particularly when the water is warm and the weather is calm.
That's why blue-green algae are most common in Florida in
the summer and early fall, with its high temperatures and
abundant sunlight, although they can occur at any time.
- Waters that flow slowly with low turbulence – such as impounded rivers, dams, or water storages – are at particularly high risk of algal blooms.
- Blue-green algae growth can become seemingly explosive
when lots of nutrients are present, providing a rich feast
that can then cause “blooms” that may look like floating
carpets of blue-green algae turning the water green. Many
other states, and countries for that matter, are
experiencing problems with algal blooms.
Are the blue-green algae blooms a new problem?
- Algal blooms are not a new phenomenon. Algal
blooms were documented in Florida’s coastal waters as early
as the 19th century. However, increased nutrient loading in
our waterways has likely contributed to increased
frequencies of blooms in our freshwater systems.
- 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 blue-green algae. 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 blue-green algaeand
their toxins (cyanotoxins) in Florida waters. For more information on this topic, please visit
Task Force Blue-Green Algae Studies.
How long do the blooms last?
- Blooms can last days, weeks or months, depending on conditions. Scientists cannot predict when or where blooms will occur or how long they will last; the blooms run their course and dissipate naturally.
Can blue-green algae blooms be treated?
No. The Florida Fish and Wildlife Conservation
Commission does not recommend treatment because it may
release the toxins.
The Bureau of Invasive Plant Management does not favor, and does not issue permits for, the application of algaecides to treat blue-green algal blooms in surface waters of the state. Such treatments are generally not very effective and would need to be repeated frequently, potentially resulting in unacceptable levels of algaecide in surface water bodies.
Surface water bodies used as drinking water reservoirs may be treated on occasion by water treatment plants in some counties. These treatments are exempt from permit requirements related to the application of algaecides in surface waters of the state.
Are large blue-green algae blooms harmful to lake/river ecosystems and cause fish kills?
- Blooms of blue-green algae that last more than a few months
can be harmful to lake/river ecosystems and cause fish kills
because of the decrease in oxygen levels and direct ingestion in
the food chain:
- Persistent blooms block sunlight that
feeds plants growing on the bottom of lakes,
resulting in the loss of rooted aquatic
vegetation, which is valuable fish habitat.
Intense blooms can cause extreme fluctuations in
daytime and nighttime water oxygen levels, due
to the oxygen produced during the daytime
photosynthesis and the oxygen consumed during
the nighttime respiration. The nighttime
respiration as well as the decay of the
blue-green algae, can consume much of the oxygen
in the water, causing fish to die.
- Algae use sunlight to make food and are
eaten by microscopic animals (zooplankton).
Small fish eat the zooplankton, and larger fish
and other large animals eat the small fish.
However, blue-green algae are often difficult to
eat or are of poor nutritional value for
zooplankton. Consequently, zooplankton,
particularly types that are the best fish food,
often decline during blooms. This decline can
impact the number of desirable game fish.
What is the state doing about the blue-green algae blooms?
- As part of our mission and responsibilities, the state –
including Florida Department of Environmental Protection,
Florida Fish and Wildlife Conservation Commission, Florida
Department of Health, St. Johns River Water Management
District, South Florida Water Management District-and the
University of Florida is responsibly concerned, not alarmed,
about the current situation as we continue to monitor,
evaluate and provide information to other concerned local,
county, state and federal agencies.
- The state is looking to increase the frequency and
expand some of its current routine algal bloom monitoring in
the major water bodies to try and get a better understanding
of the phenomenon. This information will be shared with our
government partners and the public as it becomes available.
- We’ve increased communication with:
- Local government
- Elected officials
- Partnering agencies
- General public
The St. John’s River Water Management District
regularly monitors algal growth in the St. John’s River and
routinely collects water and algae samples, particularly during
periods when conditions are right for algal proliferation.
Whom can I contact to report a blue-green algae bloom or to get more information about water quality?
- There are several toll-free hotlines available for people to report fish kills or illness associated with blue-green algae.
- Fish Kill Hotline (Florida Fish & Wildlife Conservation Commission) 800-636-0511
- Human Illness (Florida Aquatic Toxin Hotline) 888-232-8635
Are there web sites for more information about blue-green algae?