Information from the Wisconsin Department of Natural Resources
What are blue-green algae?
Blue-green algae, also known as Cyanobacteria, are a group of photosynthetic bacteria that many people refer to as "pond scum." Blue-green algae are most often blue-green in color, but can also be blue, green, reddish-purple, or brown. Blue-green algae generally grow in lakes, ponds, and slow-moving streams when the water is warm and enriched with nutrients like phosphorus or nitrogen.
When environmental conditions are just right, blue-green algae can grow very quickly in number. Most species are buoyant and will float to the surface, where they form scum layers or floating mats. When this happens, we call this a "blue-green algae bloom." In Wisconsin, blue-green algae blooms generally occur between mid-June and late September, although in rare instances, blooms have been observed in winter, even under the ice.
Learn more about blue-green algae
- More information and resources about blue-green algae are available on our online resource folder (Google Drive).
- You can find more information about the possible health effects of blue-green algae at the Wisconsin Department of Health Services website. You can also report human and animal illnesses potentially related to blue-green algae exposure at this website.
- For more information about blue-green algae, check out the Wisconsin Department of Natural Resources website.