Blue-Green Algae Blooms in the Capital Region

May 26, 2022 (updated Aug 16, 2022, 1:27pm)

As of Aug. 16 this advisory has been lifted for Wrigglesworth Lake but remains in effect for both Lower Thetis Lake and Prior Lake.

The Capital Regional District advises, in consultation with Island Health, that there are currently blue-green algae blooms in Lower Thetis Lake and Prior Lake, both located in Thetis Lake Regional Park.

These algae are known toxin producers. Ingesting water containing these cyanotoxins may cause a range of symptoms—including headaches and abdominal pain in humans—and can lead to lethal liver damage in dogs.

Park visitors are advised to avoid swimming at both Lower Thetis Lake and Prior Lake and to keep animals on a leash to prevent them from drinking or swimming in the lakes until this advisory has been lifted.

The algae usually produce a visible blue-green sheen, which appears as surface scum on the water. Not all blooms are easy to see and toxins can still be present in the water even if you cannot see a bloom. Blooms are unpredictable and may occur at any time.

To learn more about blue-green algae, please visit:

The advisory for Wrigglesworth Lake, located in Wrigglesworth Lake Regional Park adjacent to Sooke Hills Wilderness Regional Park, has now been lifted.