Blue-Green Algae Confirmed In Lake St. John, Ramara


The Simcoe Muskoka District Health Unit (SMDHU) has been advised by the Ministry of Environment, Conservation and Parks (MECP) that additional laboratory tests confirm the presence of a blue-green algae bloom now impacting all of Lake St. John. This advisory expands on the previous notice issued on October 4, 2019 advising of a blue-green algae bloom in the south west end of Lake St. John.

Wind and water currents can change the location of algae blooms, which may make the water look bluish-green, or like green pea soup or turquoise paint. Swimming and other water sport activities should also be avoided in areas where a blue-green algae bloom is visible.

The health unit is advising residents around the southwest end of Lake St. John, to avoid using the lake water for drinking or food preparation, including breastmilk substitute (infant formula). Boiling the water will not destroy the toxins, and home treatment systems should not be relied on.

Exposure to blue-green algae, whether for drinking, swimming, cooking or through eating fish caught from the southwest end of Lake St. John, may result in illness. Adverse health effects are mainly caused by drinking water that is contaminated with blue-green algae toxins. Symptoms from consuming toxins can include headaches, fever, diarrhea, abdominal pain, nausea and vomiting, and can be more serious if water is swallowed in large quantities.

SMDHU and the MECP will continue to monitor the lake and updates will be posted on the health unit’s website at

To learn more about blue-green algae visit the health unit website at, or call Health Connection weekdays from 8:30 a.m. to 4:30 p.m. at 705-721-7520 or 1-877-721-7520.


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