Blue-Green Algae


What are cyanobacteria and why should we sample?
Cyanobacteria (also know as blue-green algae) are aquatic microorganisms able to produce natural toxins, called cyanotoxins. Naturally present in the water, cyanobacteria only become a problem when they proliferate. If conditions are favourable, for example when large quantities of phosphorus can be found in the water, cyanobacteria can reproduce quickly. When this occurs, they form what are referred to as algal blooms, which are visible to the naked eye, and can generally be found floating on the surface of the water. These blooms are generally green or turquoise in colour and can look like spilled paint floating on the surface, or like froth or scum lining the shores or again, like floating pea or broccoli soup. Alternatively, certain rarer species of cyanobacteria have red pigments and will look like masses of varying shades of red spread or diffused on the water (even from underneath sheets of ice). For examples of cyanobacterial blooms, please consult the MDDELCC identification guide (French only) Guide d’identification des fleurs d’eau de cyanobactéries available in their offices or online at (French only).

Health risks for bathers and other recreational users:
When cyanobacteria produce toxins, they can be harmful to human health. It is strongly recommended to avoid contact with this contaminated water and to avoid ingestion as well. Symptoms generally include diarrhea, nausea, vomiting and abdominal pain when ingested and irritation of the skin, eyes or throat after contact has occurred. If large quantities have been ingested, cyanotoxins can affect the digestive system, the liver and the nervous system.

What to do:
If you suspect the presence of algal blooms in a lake, you must contact the MDDELCC without delay at 819‑772‑call their environmental emergency line ‘Urgence-Environnement’ at 1‑866‑694-5454. You can also go online and fill out the visual sighting of cyanobacterial bloom report:

Lakes impacted by blue-green algae

Since few years, several reports of blue-green algae blooming have been made on some lakes in Val-des-Monts, including Baie Mud, Eau Claire, Gilmour, Lachaine, McMullin, Saint-Pierre, Truite Maigre, Twin and Vert.


Report the presence of blue-green algae



What to do in the presence of  blue-green algae