The CRD has issued an advisory for Prior Lake, located at the north end of Thetis Lake, after water samples tested positive for blue-green algae and associated cyanotoxins.
Authorities are warning people against swimming and to keep animals on a leash to prevent them from drinking or swimming in the water.
The algae usually produce a visible blue-green sheen, which appears as surface scum. However, not all blooms are easy to see and toxins can still be present in the water even if you cannot see them.
Algae blooms are known toxin producers and can be harmful to both humans and animals.
While blooms are unpredictable, they typically occur over the winter months from November to March.
Ingesting water containing the algae may cause a range of symptoms, including headaches and abdominal pain in humans, and can lead to lethal liver damage in dogs.
There are no signs of blue-green algae at Upper or Lower Thetis Lake.
