Blue-Green Algae at Lower Thetis Lake

May 26, 2022 (updated Nov 28, 2022, 11:29am)

People and pets should avoid swimming in Lower Thetis Lake (Thetis Lake Regional Park).

The Capital Regional District (CRD) advises, in consultation with Island Health, that there is a blue-green algae bloom at Lower Thetis Lake, located within Thetis Lake Regional Park.

The advisories for both Prior and Elk Lake have been lifted.

Blue-green algae can produce cyanotoxins. Visitors are advised to avoid swimming at Lower Thetis Lake and to keep animals on a leash to prevent them from drinking or swimming in the lake until the advisory has been lifted.

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

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.

Please visit and Twitter @crd_bc for updates on active alerts. To learn more about blue-green algae visit our website.