Accelerated warming driving ecological change in Great Slave Lake

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Great Slave Lake in Yellowknife (Photo: wikimedia)
Great Slave Lake in Yellowknife (Photo: wikimedia)

Researchers from Queen’s University and Environment and Climate Change Canada have discovered that accelerated 21st -century warming has triggered a striking shift in algae composition in Great Slave Lake, North America’s deepest lake. The findings were published today in the journal Proceedings of the Royal Society B , and suggests that declining ice coverage and other climate-related changes have marked the crossing of an important ecological threshold.

Using information preserved in dated lake sediment cores as an archive of past ecosystems changes, the research team uncovered a rapid restructuring of algal communities linked to declining lake ice cover and other climate-related changes, which were unparalleled over the last 200 years.

"Such a pronounced change at the base of the food chain is a clear indication that this ’northern Great Lake’ is entering a new ecological regime," explains Dr. Kathleen Rühland, lead author and a senior research scientist at Queen’s University’s Paleoecological Environmental Assessment and Research Lab (PEARL) . "These microscopic algae are fundamental to lake ecosystem functioning and these big shifts are a sure sign that the entire lake is changing and changing fast."

These changes have unknown ramifications for fisheries and aquatic ecosystem functioning and their impact on First Nations, Métis, and other northern communities. Great Slave Lake also supports the largest commercial, recreational, and Indigenous freshwater fishery in the Northwest Territories, with approximately 60 per cent of the territory’s population living near the shorelines of the lake.

Arctic temperatures have risen by as much as four times the global average over recent decades, with a notable acceleration since the beginning of the 2000s.

There is limited data on northern lakes, and much of what is currently known about Great Slave Lake can be attributed to detailed studies by the late D.S. Rawson (University of Saskatchewan) and his colleagues during the 1940s and 1950s. These and other historical lake surveys allowed the researchers to ground-truth (information that is known to be real or true, provided by direct observation and measurement) their paleolimnological (lake sediment) findings.

"Our previous work has shown that recent warming has resulted in shorter ice cover periods and other predictable changes in many small and medium-sized lakes throughout the Arctic, with important ecological repercussions," says co-author Dr. John Smol, Professor of Biology at Queen’s and co-director of PEARL. "In contrast, very large, deep and (until recently) extensively ice-covered northern lakes such as Great Slave Lake have been partly sheltered from climate warming, but are now entering a new ecological state."

For more details, visit the Proceedings of the Royal Society B.