Blue/ Green Algae at Reesor Lake
CYPRESS HILLS – August 7, 2026
Blue/Green Algae comes in different colours - Photo Courtesy of Alberta Lake Management Society
Health officials have issued a cyanobacteria advisory for Reesor Lake, that is the name for blue-green algae. The name is a bit of a misnomer as these potentially dangerous blooms can not only be blue-green, they can also be green, brown, red, pink or blue. They often smell musty or grassy.
A Quick Science Note
Not all cyanobacteria produce toxins but you cannot tell the difference just by looking at them. The species that can produce toxins do not always produce them, and they can switch on and off depending on conditions.
Since there is no way to know for sure, the safe rule is to treat every bloom as if it is toxic. This is especially important because some of these toxins can be deadly to pets and even humans.
AHS Recommendations For Blue/Green Algae
Here is what you need to know if you are heading to Reesor Lake or any other water body with a blue/green algae bloom:
Do not swim or wade anywhere you see the blooms. Avoid contact with the water or scum on the shore.
Do not drink or cook with the lake water. Boiling does not remove the toxins, so stick to bottled or tap water.
Keep pets away from the water. The algae can be fatal to dogs, so do not let them swim, drink, or even sniff the scum. Symptoms can appear within hours, and death can occur rapidly.
If you touch the water, wash off with clean tap water as soon as possible.
The Good News About Fish
You CAN eat fish fillets from Reesor Lake. The toxins from the algae tend to stay in the guts and liver of the fish, not in the muscle meat that becomes your dinner. Make sure to clean the fish properly.
Do not eat whole fish or fish trimmings, and do not feed those parts to your pets.
Where to Actually Swim
Reesor Lake does not even have a beach, it is mostly used by anglers wanting a quiet place to go fishing.
The real swimming spot in Cypress Hills is Elkwater Lake; you can swim, boat, water ski, or just float around. It is the largest lake in the park and the place to be when the temperatures rise.
For fishing fans, Elkwater Lake has naturally occurring perch and pike.
Spruce Coulee Reservoir is also stocked with trout and walleye, but like Reesor Lake, it has no beach.
What Symptoms to Watch For
If you or your kids do end up touching the bad water at Reesor, watch for symptoms like rash, sore throat, red eyes, swollen lips, fever, nausea, or diarrhea. These can show up in one to three hours and usually clear up in a day or two.
Kids and pets are more sensitive, so keep an extra close eye on them. For pets, signs of poisoning can include drooling, muscle tremors, difficulty breathing, and even sudden death.
The Bottom Line
Reesor Lake is off-limits for swimming right now, but that is no big loss because it was never the place for that anyway. Head to Elkwater Lake for your beach day and enjoy the sun. If you want to fish, Reesor Lake fillets are safe as long as you clean them properly and toss the guts.
Remember, even though not every bloom is toxic, you cannot tell the difference by sight, and the stakes are too high to take chances.
If you have questions or feel sick after a visit, call Health Link at 811 or check www.ahs.ca/bga for updates.
Resources
Cyanobacteria (blue-green algae) and their Toxins - ALMS
