Do a jar test if you suspect blue-green algae

If you see a blue-green film (looks like paint or pollen) floating on the surface of the water, follow these steps:

1. Take a photo and send it to info@lacnotredame.org, tell us where it is - avoid swimming near the bloom, keep children and pets away, and if it is within 3m of your water intake, stop drinking the water
2. Use a clean jar and fill it about 3/4 full with water from the film and just below it, use gloves and wash your hands and wipe the outside of the jar afterwards
3. Place the jar in the fridge to let the contents settle
4. After two hours, take a look at the jar in the fridge - if the algae has floated up to the surface and is forming a ring, or is in a layer at the top, it is likely blue-green algae. Send another email to report the results of your test. We’ll send an email to warn all members to stay at 3 meters away until 24 hours after the bloom has disappeared.
5. Follow Quebec’s advice on how long to avoid the area, and what to do if you have symptoms of exposure: Preventing health problems associated with blue-green algae blooms

Photo of jar tests from Lac Notre Dame:

In 2021, regular algae stayed mixed in water after 2-4 hours in fridge, versus a jar in 2020 where Blue-green algae floated to form a layer at the top.