Canada's lakes are becoming less blue — but that could be good for fish

If you drive the Icefields Parkway through the Canadian Rockies, you'll pass multiple turquoise-coloured lakes that are popular with tourists for taking photos. 

The lakes get their iconic colour from rock flour, which is similar in appearance to baker's flour used for making bread. Rock flour is made from glaciers grinding rocks into powder, which can take thousands of years. 

The flour then flows into streams, rivers and lakes, becoming suspended in the water column, reflecting a turquoise colour. 

But as glaciers retreat or disappear with climate change, less flour is produced, resulting in clearer lakes. 

"They'll resemble the lakes that we see in central Alberta," said Rolf Vinebrooke, a freshwater ecologist at the University of Alberta.

Instead, the lakes will become a more sapphire blue, he said.

This change is already happening. 

For example, Curator Lake and Geraldine Lakes in Jasper National Park have already become clearer. 

 "There's a lot of unique biodiversity in these glacially fed Alpine lakes and streams that will get lost," Vinebrooke said. 

One unique species that could be at risk is a bright red copepod called Hesperodiaptomus arcticus, which is about the size of a pen tip. 

"It [colour change] might not be a good thing for those particular species," said Janet Fischer, a biology professor at Franklin and Marshall College in Pennsylvania.  

As lakes become clearer, sunlight can penetrate deeper into the water, which fuels algal growth. Less glacier ice means warmer water, resulting in a more productive lake.

As the lakes warm, their environment may become more benign, said Fischer, allowing more widespread species to invade and potentially out-compete the unique ones, like Hesperodiaptomus arcticus.

LISTEN | The future of glacier lakes 

Fischer and her husband, Mark Olson, have studied and documented lake colour in the Canadian Rockies for 18 years.

"I find these lakes beautiful in all their stages, but there is a sadness when you have spent your life's work documenting a change that humans have accelerated," she said. 

"The lakes will still be beautiful. But they'll be different."

Losing blue 

Blue is not a common colour in the natural world. 

Less than one-third of lakes in the world are blue, according to a study from the U.S. that used satellite imagery to map colour changes in more than 85,000 lakes across the globe between 2013 and 2020.  

The study also found that algal blooms in some lakes in North America are becoming increasingly common. 

With a warming climate, the study predicts 10 per cent of blue lakes could become green or brown. 

Other than turquoise lakes, most blue lakes get their colour from having little organic material in the water, said Xiao Yang, one of the authors behind the study. He is an assistant professor in the department of earth sciences at Southern Methodist University in Texas. 

Blue lakes are found at higher elevations with high precipitation and winter ice cover. Whereas green or brown lakes are generally in drier regions, continental interiors and coastlines. 

The bluest or clearest lake in the world is Crater Lake in Oregon, according to Yang.

This shift also shows that entire lake ecology is changing and allowing different or new species to thrive, Yang said. 

"It can change the whole food web."

What does this mean for fish?  

In B.C., glacier retreat provides more habitat for cold-water fish, particularly salmon, said Matthew Sloat, science director for the international organization Wild Salmon Center. 

As glaciers melt, waterways are forming after being previously buried beneath sheets of ice. 

"Some areas may become more productive in the future," Sloat said. 

Warmer water, without glacier flour, results in a more productive lake, meaning more food could be available for fish. 

"Fisheries have emerged because of glacier retreat," he said.  

However, climate change still challenges aquatic life, mainly as some waterways may dry up during the summer if glaciers disappear. 

 "I don't want to suggest that things get better and better as glaciers retreat because that's absolutely not the case," he said. 

Even if more habitat becomes available, fish still have to be able to access it. But this could be problematic if there's a massive waterfall, which can act as an obstacle.

Another problem is if lakes change colour and warm too quickly. 

"It depends really on the degree to which it happens. If it happens very rapidly, the ecosystem might not readily adjust," said Rolf Vinebrooke with the U of A. 

"You don't really know what you've lost until it's gone."