Blue-green Algae

For details on blue-green algae advisories visit the Alberta Health Services (AHS) website, at:

Quick facts about blue-green algae in Alberta

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Blue-green algae are actually common, naturally occurring bacteria, known as cyanobacteria.

From early June to mid-September, when the days are sunny and hot, cyanobacteria may accumulate to the point that a bloom is visible at many of Alberta's nutrient-rich lakes.

Lakes with blue-green algal blooms will undergo visible changes - otherwise clear, transparent water may suddenly become soupy in appearance, often turquoise, bright blue, gray, tan or even red in color.

Some bloom-forming cyanobacteria can produce toxins that, if contacted, may cause skin and eye irritation, or, can result in intestinal discomfort or severe illness in humans if ingested.

Consumption of sufficient quantities of cyanobacterial toxins can lead to death in livestock, pets or wildlife.

When blue-green algal blooms decompose they can cause a sewage-like odour that may be offensive to recreational users.

Fish are exposed to toxins from cyanobacteria during feeding or through the gills during breathing. Toxins in the water may cause damage to the liver or nervous system of fish that rarely results in death. Fish can survive much higher levels of toxins from cyanobacteria than mammals can.

Rapid decomposition can also deplete the water of oxygen and produce high levels of ammonia, which can kill fish and other aquatic animals.

The hot weather that contributes to blue-green algae blooms also depletes water oxygen levels and cause fish die-offs.

Toxins from cyanobacteria have been shown to accumulate in the liver of exposed fish. Small amounts have also been shown to accumulate in kidneys, blood, gill, bile, intestines and brain. It is recommended that people limit their consumption of fish organs, including the skin.

Prevent your pets from eating fish caught from a lake with blue-green algae.

Studies in Alberta indicate that toxins from cyanobacteria are unlikely to accumulate in the flesh of fish at levels high enough to be hazardous to humans. Correctly gutted or filleted fish represent minimal to no health hazard to human consumption.

A number of government ministries are working together to keep Albertans informed. Alberta Health Services monitors approximately 40 public recreational sites on 30 lakes, based on the popularity of the recreational site and water quality indicators.

Alberta Environment and Parks is monitoring 50 - 60 whole lake sites, including many of the lakes being monitored by Alberta Health Services.

Whole lake monitoring involves collecting and analyzing samples that represent the average quality of the whole lake rather than sampling that only represents the water quality of a limited are such as the shoreline of a beach.

  • Treat any algae bloom with caution
  • Do not drink from bloom-infested lakes and reservoirs. Do not drink any untreated surface waters. Boiling water will not reduce the risk.
  • Do not swim or wade, or allow your pets to swim or wade, in any areas where blue-green algal blooms are visible. Areas of the lake where a bloom in not visible can still be used for recreational purposed, even while an advisory is in place.
  • Provide alternate sources of drinking water for domestic animals and pets

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Updated: Aug 6, 2021