For the third summer in a row, Yellowknife’s Jackfish lake is experiencing an algae bloom.
The phenomenon, known as a blue-green algae bloom, was first noticed to be more prevalent in 2013 and has since been observed each summer.
The bloom has likely been more noticeable in the last few years because of an increase in the lake’s nutrients, says Judy McLinton, manager of communications with environment and natural resources.
“Blue-green algae generally grow in lakes, ponds, and slow-moving streams when the water is warm and enriched with nutrients like phosphorus or nitrogen,” McLinton says.
Pam Coulter, communications manager with NTPC, says the nearby Jackfish power plant likely isn’t connected to the change in colour.
“We haven’t done anything different at Jackfish power plant,” she says.
The city of Yellowknife says they expect to see test results from the lake in August.
Blue-green algae are most often blue and green in color, but can also be reddish-purple or brown.
The algae can produce toxins that cause illness, skin rashes and in rare cases death, especially among animals. People should not swim, fish, or let their pets go in the water.
Because the algae depend on nutrients in the lake, the bloom can last anywhere from a few days to several months.
As soon as nutrients are depleted, blooms quickly die off.
“The remaining bacteria will remain in the lake, but at a depth that isn’t often visible from the surface,” McLinton says. “Algal blooms clear up on their own when conditions become less favourable.”