The Simcoe Muskoka District Health Unit (SMDHU) has received test results from the Ministry of the Environment, Conservation and Parks (MECP) confirming a blue-green algae bloom impacting the southwest shoreline of Longs Lake, Huntsville.

Many species of blue-green algae (also called cyanobacteria) have the potential to produce toxins that are harmful to the health of humans and animals when exposed in large amounts. Due to the confirmed presence of the bloom, we are asking residents to exercise caution and recognize that toxins may also be present.

As a precautionary measure, the SMDHU urges the community to avoid drawing or drinking water from private water supplies that are impacted by the lake where blue-green algae has been identified and to take the following precautions:

  • Do not use a private water supply that is impacted or draws water from this area of the lake for the preparation of infant formula.
  • Do not allow pets or livestock to drink or swim in the water where an algae bloom is visible.
  • Fish taken from waters with cyanobacterial blooms have the potential to contain toxins. Exercise caution when eating fish caught in water where blue-green algae blooms occur.
  • Do not use herbicides, copper sulphate or other algaecides that may break open algae cells and release toxins into the water.
  • Avoid water sport activities where an algae bloom is visible.

The health unit strongly recommends seeking medical attention if symptoms such as skin, eye or throat irritation, allergic reactions or breathing difficulties occur following contact with the blue-green algae bloom. Anyone who comes into contact with blue-green algae should wash with soap and water or rinse thoroughly with clean water. Swimming, bathing or showering with water not visibly affected by a blue-green algae bloom is not expected to cause health effects.

SMDHU and the MECP will continue to monitor the lake and updates will be shared as they are made available.

For more information about blue-green algae please visit