Blue-Green algae: What do you need to know?

Blue-green algae is a cyanobacteria present in all Alberta lakes. It grows best in still or slow-moving water when the weather is warm, which is why we see more blooms in the summer. When phosphorus and nitrogen are present, the bacteria will reproduce more quickly.

Blue-green algae is already beginning to make an appearance this summer in our Alberta lakes. This year, Alberta Health Services announced they would be changing the way they warn the public about the blooms.

So what do you need to know to stay safe on the water?

  1. The new regulations will inform you if cyanobacteria is present, but you’ll only be cautioned to avoid the water if a bloom is visible.

In the past, lake users were warned not to swim or wade in lakes if the bacteria was present at all. Now, advisories will be posted if the bacteria is present, but lake users will only be cautioned to stay away from physical signs of a bloom. It’s important to remember that blooms can move rapidly from location to location, so look before you swim!

  1. The warning will stay in place until the risk is no longer present.

Make sure to regularly check the Swim Guide and AHS for updates on cyanobacteria advisories, and do visual checks of your water body before swimming, wading or drinking.

  1. Blue-green algae is extremely toxic, and will make you ill – even after boiling or filtering the water.

Avoid all contact with blue-green algae, and wash with soap and water if you come into contact with it. Contact with blue-green algae can lead to skin irritation and/or reactions in the eye, ear, nose and throat. It can also lead to more severe side effects, including headaches, diarrhea, vomiting, and fever.

  1. If you know cyanobacteria is present in your lake, make sure to look for physical signs of a bloom.

Blooms generally smell pungent and strongly grassy. They coat the surface of the water and look like a blue or green scum, though they can range in colour from white to red to brown.

  1. If you see a bloom, let your local health unit know and send us an email.

If you see a bloom and there is no advisory posted, mak sure to call your local health unit so they can share the advisory on their website, through social media, and with local media outlets. Sending us an email makes sure we can create a pollution report, helping spread the word and protect the health of our watershed community.


Algae. (2015). Rural Consolidated Industries LTD. Retrieved from