Toxic Algae (Harmful Algae Blooms)

Image of algae blooms in a lake.

Algae is common and natural to our waters in Colorado. But a certain type of algae can produce toxins that can harm people, animals, and the local environment. 
Toxic algae or harmful algae blooms are made up of what many people call blue-green algae. Technically, these organisms are a special type of bacteria called cyanobacteria or cyanoHABs. Although these organisms naturally occur in Colorado waters, they become a problem when they multiply rapidly, resulting in a dense cyanobacteria concentration or bloom. The blooms can become harmful when the cyanobacteria produce toxins. Learn more below.
General public
Toxic Algae FAQ
What toxic algae looks like, how to test your water, health impacts, and more
Toxic Algae Flyer
Graphic of toxic algae facts and symptoms associated with exposure
Helpful brochure from New York Sea Grant regarding toxic algae and pets
Where toxic algae comes from, health effects, and actions you can take
Toxic algae illnesses, symptoms, sources of exposure, and risk factors
Recreational and drinking water professionals​
Testing, reporting, and managing toxic algae in the water
Monitoring guidance for public water systems that rely on surface water
Only post these signs using the Risk Management Toolkit flowchart (page 5)
Toxic Algae in Colorado 
Some bodies of water in Colorado are routinely monitored and tested for algal toxins to protect the health and safety of water users. Our toxic algae dashboard displays historic harmful algal bloom information submitted to the department. Data is voluntarily reported and does not represent all recreational bodies of water in Colorado. They do not represent current conditions of the water body so we recommend to always examine a body of water for warning signs before allowing children, pets, or yourself to come into contact with water. 
ToxCall Colorado