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The Provincial Park Superintendent advised us on Oct 13, 2021, that there was a blue-green algae bloom near boathouse cove and Slack Bay.  Water was tested and the Public Health Inspector for Leeds and Grenville  confirmed blue-green algae blooms with elevated toxins.  The bloom has since dissipated.  We are sharing the following information on blue-green algae to make you aware and to educate our members. 


Blue-green algae blooms are a natural seasonal phenomenon that may appear in our lakes, rivers and ponds. Many of these blooms are relatively harmless; however, some species have the potential to produce toxins which may be harmful to people and animals. The presence of blue-green algae and its toxins can only be confirmed through a laboratory test, so we recommend taking a cautious approach when you suspect a blue-green algae bloom. Toxins that can cause skin irritation, nausea and vomiting, and in higher concentrations, liver problems are released when the cells break down.


The health unit advises people using surface water for recreation and drinking, to become familiar with blue-green algae so they can make informed decisions on when to avoid contact with the water. Algae blooms do degrade with time; however, it is not possible to say whether the toxins have completely left the area. Once the toxin is released from the cell, where it goes is dependent on the local characteristics of water movement in the area. The toxin will eventually be diluted into the body of water as any other soluble compound.


Drinking Water

Surface water is never a safe source of drinking water without effective treatment. The toxins released by blue-green algae are not removed by commonly used treatment methods such as boiling, chlorination or ultraviolet light treatment. Consult a water treatment specialist if your drinking water comes from the lake. You may want to choose another source of water for drinking.


Recreational Water Use

Avoid activities that increase your exposure to toxins in the water during an active algae bloom. When deciding whether to resume recreational use of the water after a blue-green algae bloom (swimming and water sports) consider the following factors:

  • Faster moving water will dilute and move the toxins out of an area more quickly, further decreasing the risk to health. Each property will have a different water flow pattern, so a local assessment is useful to further assess risk.

  • Skin irritation is the first sign that the level of toxin is significant in the water, so if this occurs, it is important not to go in the water. A few more days will help to clear the water if it is moving well, unless another bloom has occurred. Page 1 of 2

  • The water in lakes and rivers always has the potential to be infected with bacteria, viruses and other microbes that can affect health. So it is important not to swallow the water. Young children are more likely to swallow water so it is critical to observe them carefully when in the water.

  • Be cautious about eating fish caught in water where a blue-green algae bloom has occurred. Toxins are concentrated in the liver. So avoid consuming the liver, kidneys and other organs of fish caught in an area affected by blue-green algae.


Algae exist in nature; however, they rely on certain conditions to grow. While we cannot control many of these conditions, we can influence one of the factors that affect their growth that is the nutrients available to them. You can help reduce nutrient levels entering the lake by reducing the use of household fertilizers, agricultural runoff, and ensuring your septic system is in good working order.


Residents are encouraged to contact the Spills Action Center at 1-800-268-6060 to report any new blue-green algae blooms. This way the location and number of blooms can be monitored.

Information about blue-green algae

Presentation on blue-green algae

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