Blue-green algal bloom reported in Bass Lake

The Ministry of the Environment, Conservation and Parks has advised Public Health Sudbury & Districts that results from samples taken July 21, 2023, from Bass Lake, Manitoulin Island, are positive for blue-green algae (cyanobacteria). The samples contained a species of cyanobacteria that can produce toxins.

Blue-green algal blooms could also appear in other parts of the lake. Because blooms are not anchored, they can move from one location to another through wind and water action. New blooms can also form. All residents on lakes should look for blooms in their area.

Blue-green algal blooms have an unsightly pea soup appearance and foul smell, and can produce toxins. Residents should avoid using or drinking water from areas where blooms are visible.

The highest concentrations of toxins are usually found in blooms and scum on the shoreline. These dense accumulations pose the greatest potential risks to people and pets. The algae toxins can irritate a person’s skin and, if ingested, cause diarrhea and vomiting. If a person ingests high levels of toxin, they could suffer liver and nervous system damage.

Public Health Sudbury & Districts advises people using lakes and rivers to be on the lookout for algal blooms. If you see a bloom near your property or water intake line:

• Avoid using the water for drinking, bathing, or showering, and do not allow children, pets, or livestock to drink or swim in the bloom.
• Be aware that shallow drinking water intake pipes can pump in blue-green algae.
• Do not boil the water or treat it with a disinfectant, like bleach, because it breaks open the algae cells, which releases more toxins into the water.
• Do not rely on water jug filtration systems as they may not protect against the toxins.
• Avoid cooking with the water because food may absorb toxins from the water during cooking.
• Follow the Ministry of the Environment, Conservation and Parks Guide to Eating Ontario Fish. Exercise caution with respect to eating fish caught in water where blue-green algal blooms occur. Residents should not eat the liver, kidneys, and other organs of fish.

On lakes and rivers where blue-green algal blooms are confirmed, people who use the surface water for their private drinking water supply may wish to consider an alternate, protected source of water.

For more information on blue-green algae, including a list and map of water bodies with confirmed blooms, please visit our website at phsd.ca or call Public Health Sudbury & Districts at 705.522.9200, ext. 464 (toll-free 1.866.522.9200).