How glacier loss impacts algal communities in alpine streams in the Canadian Rockies

Research assistants Chris Chan (close) and Matthew Elphick (far) prepare for algae collection below Victoria Glacier, Lake Louise. Photo Karson Sudlow

The final crux of the Bow Hut approach is a stream crossing that marks the summit push.

This stream, visible from the hut above, is responsible for many-a-wet foot during early summer, and is teeming with aquatic biodiversity adapted to the extreme conditions of glacial meltwater flowing from the Wapta Icefield.

Though rapid, freezing, and cloudy, a small number of highly specialized species of algae thrive in this and many other alpine streams throughout the Rockies. Growing along the rocky stream beds of these waters, algae form the base of alpine stream food webs and are essential for healthy mountain ecosystems. But, as glaciers disappear, these unique ecosystems have become increasingly threatened due to changing conditions in alpine streams. Progressively warmer, clearer, and slower streams could have negative consequences for biodiversity and the growth of algae that is adapted to harsh glacial environments.

Research assistant Simonne Tremblay collecting aquatic insects from Emerald glacier stream, above Emerald Lake, Yoho National Park. Simonne is using a kicknet to collect insect samples. She disturbs the stream bed to detach insects into the awaiting net. Algae are a main food source for aquatic insects in glacial streams. Photo Karson Sudlow

With support from the ACC’s Environment Fund, we set out to investigate how glacier loss impacts algal communities in alpine streams in the Canadian Rockies. Armed with an electric toothbrush, and backpacks full of hummus and veggie sandwiches, our team visited 14 alpine streams—including the stream below Bow Hut—across Banff, Jasper, and Yoho National Parks several times in August 2021 and 2022.

Humans have a complicated relationship with algae. They are best known for causing problematic eutrophication and toxic blooms in a variety of aquatic environments, and significant energy and resources are expended to manage their growth. However, algae are critical for healthy, productive alpine lake and stream ecosystems. In often barren mountain landscapes of rock, snow, and ice, algae are a crucial food source for species higher in the food web. Without this energetic base, alpine insects and fish would lack sufficient nutrients and energy needed to survive and reproduce.

To survive the turbulent summer flows of alpine streams, algae need to strongly attach to streambeds, so they aren’t swept away by swift mountain waters. This strong grip presented us a challenge to collect the samples we needed. To get the job done, we relied on electric toothbrushes. The vibrating heads are powerful enough to remove algae from rocks, and their self-timers allow us to easily replicate scrubbing time from sample to sample. You can always count on scientists to find a new role for your household items.

After two successful summers, we scrubbed algae from over 680 rocks for our study. Back in the lab at the University of Alberta, we pulled out our microscopes to identify species from the samples we collected. The initial results were positive. Glacial specialists were found at most of our sites. However, their abundances were low in streams most impacted by glacier loss. We also found that algal growth, despite improved stream conditions, was lower in those same streams.

Algae from a glacial stream concentrated onto filter paper. Black objects are Dimesa, a species of aquatic insect that are typically found in glacial streams. Photo Leslie Ogden

The concurrent decline of alpine algal specialists and their stunted growth highlight that glacier loss does likely negatively impact alpine stream ecosystems. And, as Western Canada is expected to lose hundreds of glaciers over the next century if climate change remains unimpeded, further glacier loss should only exacerbate these trends. Although long-term studies are needed to further explore and understand the specific factors driving them, these results provide us with a path to further study in order to conserve alpine stream ecosystems.

By donating to the Environment Fund, you helped us complete this study. These funds allowed us to access our sites and buy the field equipment necessary to collect our samples. Thank you for your support and interest in science. We could not have done this without you!

Next time you get your feet wet on the way to Bow Hut, or in another of Canada’s alpine streams, watch your step! You never know who you might be stepping on.

Watching your step in glacial streams

How glacier loss impacts algal communities in alpine streams in the Canadian Rockies

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