Blue-Green Algae (Cyanobacteria)

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Cyanobacteria, or blue-green algae blooms, are not common in PEI but can be a concern as some strains can produce toxins that are harmful to human or animal health. In PEI cyanobacteria can be found in shallow, warm, and slow moving or still water (including freshwater ponds). Under certain conditions cyanobacteria can quickly multiply or 'bloom'.  Cyanobacteria blooms can appear as a bright turquoise green (hence the name blue-green algae), but colours can also vary from olive or yellow-green to dark green and even purple. When a bloom is very heavy, mats or scums can form on the surface of the water. 

The cause of cyanobacteria blooms is not certain, but it is thought to be related to levels of phosphorus in the water. Although cyanobacteria blooms are common in other parts of Canada, since 2004 only the blooms listed below have been documented in PEI:

Cyanobacteria Blooms
Date Location
October 2004 MacLure’s Dam, Murray River
July - August 2005 MacLure’s Dam, Murray River
July - August 2005 Clark’s Pond, Cavendish (PEI National Park)
July - August 2008 Clark’s Pond, Cavendish (PEI National Park)
August - October 2010 MacLure’s Dam, Murray River
August - October 2013 MacLure’s Dam, Murray River
July 2015 Campbell’s Pond, Cousin’s Shore
August – October 2015 Doyle’s Pond, St. Felix
August - September 2016 Clark's Pond , Cavendish (PEI National Park)
August 2018

MacLure's Dam, Murray River

September - October 2018

Treatment Lagoon, O'Leary

August - September 2020 MacLure's Dam, Murray River
August 2022 Black Pond, Souris
August 2022

MacLure’s Dam, Murray River

July 2023 Black Pond, Souris
July 2023 Campbell’s Pond – Dalvay
August 2023 MacLures Dam – Murray River
August 2023 Long Pond - Dalvay
June 2024 Black Pond, Souris
June 2024 MacLure’s Dam, Murray River
June 2024 Parson's Creek, Stanhope
June 2024 Point Deroche Pond, Blooming Point
July 2024 Ponds Road Pond, Pinette

What are the health concerns?

Cyanobacteria blooms can sometimes produce toxins which can cause skin rashes and irritation to the eyes of swimmers, boaters, or others who come into contact with the toxins.  Humans who accidentally drink water containing large amounts of cyanobacteria can experience nausea, vomiting, sore throat, diarrhea, or cramps. Livestock, pets, terrestrial wildlife, and aquatic life can also be harmed.

Because blue-green algae blooms may have the potential to produce toxins, it is wise to treat them with caution. If a heavy growth of blue-green algae is confirmed, PEI's Chief Health Officer will issue a public advisory.  Signs will be posted advising the public to avoid swimming in, or eating fish from the water and to keep animals from drinking the water.

The only way to confirm whether or not a particular bloom is toxic is through laboratory analysis.

What do I do if I see blue-green algae?

If you see what you suspect is a blue-green algae bloom, please contact the Department at (902) 368-5044  or, if after hours, at 1-800-565-1633 as soon as possible. 


Date de publication : 
le 17 Juillet 2024
Environnement, Énergie et Action climatique

Renseignements généraux

Ministère de l'Environnement, Énergie et Action climatique 
Immeuble Jones, 4e étage
11, rue Kent
C.P. 2000
Charlottetown (Î.-P.-É.) C1A 7N8

Téléphone : 902-368-5044
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Télécopieur : 902-368-5830
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