The blue-green algae advisory issued for Cochrane Lake in August was lifted by Alberta Health Services (AHS) on Nov. 8.
According to Medical Officer of Health Dr. Judy MacDonald, blue-green algae, officially known as cyanobacteria, are microscopic organisms that are naturally present in lakes and streams in low numbers, but can increase rapidly with warm temperatures.
“When the water receives a lot of sunlight, the algae can form blooms that will discolour the water or produce scum on the surface,” said MacDonald in August when the advisory was first issued.
“It’s a natural phenomenon that has to run its course. It’s up to nature to decide when the lake will be back to safe conditions.”
Five bodies of water in the Calgary Zone, including Cochrane Lake, were recently deemed safe by AHS.
“Recent weather has cooled water temperatures in lakes to such an extent that blue-green algae is no longer a concern,” stated an AHS press release.
AHS Medical Officer of Health for the Calgary zone Dr. Richard Musto said AHS has a routine recreational water monitoring program in place.
“Through the monitoring done via this program, it was confirmed that water temperature is of such coolness as to render it impossible for blue-green algae to survive, and likewise, the toxin that is produced was confirmed to no longer be present,” said Musto.
He added because the growth of blue-green algae is “determined by multiple environmental factors, including weather and water temperature, it is impossible to predict whether blue-green algae will be present in any body of water, any season.”
AHS officials warned nearby residents and visitors to the five lakes placed under the advisory to stay away from the shores, not to swim or wade in the water, limit consumption of fish from the lake and not allow pets to drink the water.
The algae produces a toxin that can cause illness to animals or humans that come into contact with the water. People that drink the water as a primary water source can develop serious illnesses such as liver damage, according to officials.
Musto said there weren’t any reported cases of illness due to consumption or contact with blue-green algae contaminated water this year.
Severn Lake, located northeast of Calgary, and Eagle Lake, located east of Calgary were also lifted from the advisory.
