Disappearing and Flooding Prairie Lakes: Solving an Aquatic Whodunnit
Western Canada has the highest concentration of saline lakes found anywhere in the world, but all is not well on this spangled landscape. Of the millions of lakes, some are disappearing, some are flooding, and some are turning climate history on its head.
“Most of us would say ‘so what?’ to this,” geological sciences’ Bill Last says. “But these lakes are saline and they’re in closed basins so think of them as bathtubs; if you fill one up it will spill into another lake that may not be saline or it may have a different salinity. So you’re affecting the ecological system. You’re affecting fisheries. And you’re affecting recreational uses.”
So why are some lakes getting shallower, while others have a trend towards rising?
“It can’t be just climate change’s doing because how can you possibly have a situation where some rise and some fall if it’s all climate related. So that’s what got us started on this project.”
Last has been studying Prairie lakes since the 1980s, but in 2008 he launched a study called Disappearing and Flooding Prairie Lakes: Solving an Aquatic Whodunnit. The two main suspects are humans and nature, and they could be in cahoots with each other.
The study examines Manitou Lake in western Saskatchewan and Antelope Lake in southern Saskatchewan, both of which are receding. And Waldsea and Deadmoose lakes, brimming lakes in south-central Saskatchewan.
These lakes were chosen because of their limnology and readily-available historical records. Even so, though, the data are based on only a few cores and some records that are only 150-odd years old. Enter the snitch.
Detectives love informants and Last has a remarkable set: stromatolites, mounds formed in shallow water by algae and microbes. Their mineralogy and stable isotope composition tells Last the history of the lake’s chemistry and water levels in fine detail.
Here’s the catch, the ones they’ve found contain ikaite, a rare mineral that can only form in water 0 C and cooler; it is usually found only in saline Arctic environments, but Last and Fawn Ginn, a PhD student, were the first to report ikiate in the Prairies. What this means is it was colder – at least in the Manitou lake area – 2,000 years ago than previous paleoclimate analyses suggests.
“The implications of this are over my head,” Last said. “Everything we know suggests the temperature in Western Canada was generally consistent. To see this cold water phase that lasted 500 to 600 years was a big surprise. I haven’t wrapped my mind around it yet from a hydrological standpoint. But from a global change standpoint, I think it means we have to start thinking about rapid climate change potentially affecting the Prairies.”
Adding to the mystery of all this: why do these stromatolites form in only a few Prairie lakes and not others with similar chemistries and limnology? Last and Ginn do not yet know.
Nevertheless, the stromatolites, by revealing history, are revealing clues in this whodunnit. Right now, Last suspects a lot of could-be culprits, from industry pulling water out of basins, to farmers draining swamps into lakes, to groundwater seeping in or out of basins.
“Whatever it is though, we’ll find the culprit.”
This story originally appeared in The Bulletin on March 26, 2009.
Research at the University of Manitoba is partially supported by funding from the Government of Canada Research Support Fund.