Blue-green algae bloom confirmed on south-west shore of Sparrow Lake

Residents and visitors are advised that a blue-green algae bloom has been confirmed by the test results from the Ministry of the Environment, Conservation and Parks (MECP) along the south-west shore of Sparrow Lake in the Township of Severn.

Blue-green algae, also called cyanobacteria, can produce toxins that may be harmful to humans and animals. The Simcoe Muskoka District Health Unit is recommending that residents and visitors take precautions in areas where blue-green algae is visible.

Blue-green algae blooms can make the water look bluish-green, or like green pea soup or turquoise paint.

Precautions

Residents and visitors should:

• not drink water from private water supplies that draw from, or are impacted by, the affected area of the lake
• not use private surface water taken from the affected area to prepare infant formula
• not swim or take part in water sport activities where an algae bloom is visible
• not allow pets or livestock to drink or swim in water where an algae bloom is visible
• use caution when eating fish caught in water where blue-green algae blooms are present, as fish may contain toxins
• not use herbicides, copper sulphate, or other algaecides, as these products may break open algae cells and release toxins into the water

Possible symptoms

Symptoms following contact with, or consumption of, toxins from a blue-green algae bloom can include:

• skin, eye, or throat irritation
• breathing difficulties
• headaches
• fever
• diarrhea
• abdominal pain
• nausea and vomiting

Symptoms may be more serious if affected water is swallowed in large quantities.

The Simcoe Muskoka District Health Unit and the Ministry of the Environment, Conservation and Parks will continue to monitor the algae bloom and provide updates as available.

For more information about blue-green algae, visit smdhu.org/algae or contact Health Connection at 705-721-7520 or 1-877-721-7520, weekdays from 8:30 a.m. to 4:30 p.m.

Notification of algae bloom received via email from the Simcoe Muskoka District Health Unit on Thursday, July 9, 2026.

How to report a suspected blue-green algae bloom

If you suspect a blue-green algae bloom, contact the Ministry of the Environment, Conservation and Parks (MECP). Incidents can be reported online or by calling 1-800-268-6060.

The MECP will gather information, conduct field visits as necessary, and facilitate testing to confirm if a blue-green algae bloom is present.

If a bloom is confirmed, the Simcoe Muskoka District Health Unit and the Ministry of Environment, Conservation and Parks work together to monitor the algal bloom and provide updates to impacted residents.

Contact us

Customer Care Team
Phone: 705-325-2315
Email: customercare@severn.ca

Images: Simcoe Muskoka District Health Unit, 2025.