Blue-Green Algae (Cyanobacteria)

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, only eight have been documented in PEI in the past 12 years, as listed in the table below:

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

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 of Communities, Land and Environment at (902) 368-5044  or, if after hours, at 1-800-565-1633 as soon as possible. 

Published date: 
June 14, 2018
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General Inquiries

Department of Communities, Land and Environment
4th Floor, Jones Building
11 Kent Street
PO Box 2000
Charlottetown, PE C1A 7N8

Phone: (902) 368-5044
Toll-free: 1-866-368-5044
Fax: (902) 368-5830

CLE@gov.pe.ca