Blue-green algae: What to do if you find it

Blue-green algae characteristics

Blue-green algae, or cyanobacteria, are bacteria that naturally occur in lakes and other waterbodies. They are not always harmful but can be in large quantities.

Here are some things to look for if you think you may have spotted a blue-green algae bloom:

• Colour: often blueish-green or green like pea soup; can also be olive or reddish.
• Smell: may smell fishy or have an odor like grass clippings, sewage, garbage or gasoline.
• Consistency: like paint or soup; may appear scummy or foamy. Can form mats and blobs in large quantities.
• Location: most likely to be in warm water with little current; may be more likely to occur in watersheds with development, agriculture and/or wetland loss upstream.
• Time of year: most likely to appear in summer and early fall.

Other common species can be mistaken for blue-green algae. Click here to see some of them and compare with your sightings.