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There was a blue-green algae bloom in Yellowknife Bay. Here's what you should know about it

Tests showed this bloom wasn't toxic, but other ones could be

Posted: July 29, 2023

A milky blue substance in the water near Negus Point in Yellowknife Bay prompted a call to the N.W.T.'s Spill Line nearly two weeks ago.

But instead of finding a fuel spill, a representative of the territory's Department of Environment and Climate Change (ECC) and the Coast Guard discovered a bloom of cyanobacteria also known as blue-green algae. 

Blue-green algae can produce toxins that are harmful to people and animals, but Jeffrey Cederwall, an aquatic quality scientist with the N.W.T. government, says testing did not find toxins in this particular bloom. 

"It was, at this instance, safe," he said. 

And now, it's gone. 

Cederwall said wind likely pushed the algae into a cove of Negus Point. It was there for about a week, he said, before it spread out into a lighter bloom in the bay for a day and a half and subsided. 

Potential hazard to dogs

Blue-green algae can hurt you and your dog. 

Although this particular bloom was deemed to be safe before it subsided, Michelle Tuma, the northern Canadian veterinary specialist for Vets Without Borders, spoke to CBC News about the risks of blue-green algae in animals. 

Tuma said if the algae were developing toxins, animals that ingested it could end up with neurological or liver damage which could lead to death. 

The first indicators of poisoning would be gastrointestinal irritation, she said, like drooling, vomiting, diarrhea and possibly signs of anxiety. After that, it changes into more neurological problems, like weakness, disorientation, stumbling, not being able to stand, collapsing, being unconscious and having seizures.

Dogs showing the neurological symptoms should get veterinary care right away, she said. The earlier symptoms are more vague, she said, but if you know your dog swam in an area with a bloom or you're confident the situation is getting worse, you should get them checked out.

Blue-green algae has long been making headlines in southern Canada, where it's affecting people's use of lakes and has been blamed for the deaths of multiple dogs. 

Cyanobacteria is harmful to humans too: it can cause itchy and irritated eyes and skin if you come into contact with it, and it can cause flu-like symptoms, headache, fever, diarrhea, abdominal pain, nausea and vomiting if swallowed. 

• Some Lake Erie anglers consider algae blooms helpful but what are the health implications?

• Moncton's water supply has cyanobacteria. Here's what the city is doing about it

Will we get more blue-green algae this year?

Cederwall said the bacteria is natural and has been present in Great Slave Lake for a long time. 

What is unusual, however, is for it to grow "to excess" like it did recently. He said it likely happened because of the increased temperatures and nutrients (like phosphorus and nitrogen) in the water. An advisory from ECC said less flowing water in the Yellowknife River and sustained southern winds might also have something to do with it.

"There is potential that this could arise again through the year, although it may be in different areas," said Cederwall. "You'd be more likely to see it mid-August to early-September."

Cederwall said people should not assume future blooms are safe too. The algae's capacity to produce toxins depends on the body of water and its conditions, he said.

"If future blooms were to occur, it does take time to get results back. So if people were to encounter that while they're out camping or enjoying the water body, then you know, keeping your pet away that can't see this distinct colour, doesn't respond to it   is always a precaution."

The territory says it will continue to collect samples from the Yellowknife Bay and surrounding area for testing, to monitor the situation.