ϳԹԴ researchers sound alarm on Canada’s rapidly changing Northern Great Lakes
June 1, 2026
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In a new collaborative study, ϳԹԴ researchers, teaming up with federal government scientists, have documented striking ecological shifts in the primary producers – phytoplankton, algae, and plants that make up the foundation of the aquatic food web – of Canada’s three largest Arctic lakes.
The findings are an early warning sign for the North.
Research led by Drs. Kathleen M. Rühland and John P. Smol from ϳԹԴ’s Paleoecological Environmental Assessment and Research Lab (PEARL) has uncovered dramatic climate-driven changes in the algal communities of Great Bear Lake, Great Slave Lake, and Lake Hazen. Their findings, published in PNAS (Proceedings of the National Academy of Sciences), use information preserved in dated lake sediment cores to reconstruct two centuries of environmental change from all three of these vast northern lakes.
What they found is striking.
Around the turn of the 21st century, small open-water diatoms (a type of algae made of silica) rapidly dominated the records in all three lakes, displacing the long-established dominance of shallow-water species in Great Bear Lake and Lake Hazen and larger and heavier diatom species in Great Slave Lake. This shift closely tracks the acceleration of climate warming and a significant increase in ice-free days across the Canadian Arctic.
“This is a very rapid and ecologically significant community restructuring of these tiny algae in recent decades as the high pace of Arctic warming is driving the world’s largest Arctic lakes into uncharted territory,” says Dr. Rühland.
“A change at the bottom of the food web will cascade to upper trophic levels of these massive lakes, and is an early warning of changes to the whole lake from zooplankton to fish,” adds Dr. Smol, who recently received the Mohn Prize from the – the world’s top award for Arctic research. “Great Bear Lake is often considered the world’s most pristine truly large lake, but a lot of changes have been occurring recently under the waterline, with potential repercussions to the native cold water fish populations that northern communities depend on.”
To support their findings, the team cross-referenced their sediment data against historical lake surveys undertaken during the 1940s to 1980s, which showed the lakes remained ecologically stable throughout most of the 20th century. The recent changes represent a sharp and unprecedented departure from that stability.
This landmark research delivers an urgent message: even the largest and most remote lake ecosystems are no longer immune to climate change.
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