Lake Sundance closed to swimmers due to toxic blue-green algae bloom
Alberta Health Services warns residents to avoid contact with cyanobacterial blooms, which can cause skin irritation, rash, fever and gastrointestinal illness.
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Swimmers and waders should stay out of Lake Sundance in southeast Calgary due to a toxic blue-green algal bloom, Alberta Health Services said August 14. The cyanobacterial bloom can appear as pink, blue-green, greenish-brown scum, streaks, pea soup or fuzz balls and has a musty or grassy odour.
People who come into contact with a cyanobacterial bloom or ingest water containing the bacteria may experience skin irritation, rash, sore throat, sore red eyes, swollen lips, fever, nausea, vomiting or diarrhea. Pets should also avoid the water and should not be fed fish from the lake.
Residents should refrain from consuming whole fish or fish trimmings from Lake Sundance and should not drink or cook with its water. Boiling the water will not remove the toxins. Water that doesn't visibly contain blooms can be entered, but conditions can shift — warmer weather and wind can move blooms from one location to another.
The advisory remains in effect until further notice. AHS continues to monitor the situation.
When was the bloom first detected and how long is it expected to persist?
✓ Are other Calgary-area lakes or water bodies being monitored for similar blooms? — answered 2026-08-14, see update above
We'll update this story as answers emerge.
The facts
Why is Lake Sundance closed to swimmers?
Lake Sundance in southeast Calgary has a toxic blue-green algal bloom, according to Alberta Health Services. The cyanobacterial bloom can appear as pink, blue-green, greenish-brown scum, streaks, pea soup or fuzz balls and has a musty or grassy odour.
What health effects can cyanobacterial blooms cause?
Contact with a cyanobacterial bloom or ingestion of contaminated water may cause skin irritation, rash, sore throat, sore red eyes, swollen lips, fever, nausea, vomiting or diarrhea.
Can boiling Lake Sundance water make it safe to drink?
No. Boiling water from Lake Sundance will not remove the toxins produced by the cyanobacterial bloom.
