In the Andes, new evidence of climate change

Faster rate of warming than global average led Queen’s researchers to lakes in Ecuadorian national park

John Smol
Image by: Arwin Chan
John Smol

Queen’s scientists published a study earlier this month that shows new evidence of climate change in tropical Andean lakes.

Neal Michelutti, lead author and a senior research scientist at Queen’s Paleoecological Environmental Assessment and Research Lab (PEARL), and John Smol, co-author, Queen’s biology professor and the Canada Research Chair in Environmental Change, travelled to Ecuador to examine three lakes in Cajas National Park.

The research, published on Feb. 3 in the journal PLOS ONE, presents data collected in the summer of 2011 and looks primarily at “diatoms” — a common form of algae.

Michelutti and Smol were part of a team that also included Alexander Wolfe from the University of Alberta, Colin Cooke from the Government of Alberta, William Hobbs from the Washington State Department of Ecology and Mathias Vuille from the University at Albany, State University of New York.

One of the biggest challenges in ecological or environmental work, Smol said, is the absence of direct measurement for long-term data, particularly in remote areas.

Collecting mud from the bottom of the lake is one way to overcome this, he added, as sediment contains fossils of organisms that once lived in the lake, for example.

“And if that mud’s not disturbed — and we have ways of determining if it’s disturbed — it’s like a history book or a museum, if you like,” Smol said.

“If you can remove that history book, it’s full of information.”

The research team pushed tubes into the lake, before matching the samples, or “cores” to historical time periods using radioisotopes.

“We section [the cores] into typically half centimetre or sometimes even finer intervals — the deeper you go, the older it’ll be,” he said.

“So we can say, this is about the 1850s, this is about 1910, this is about 1980s in the core.”

Smol said a large change in the lakes’ fossils was found to coincide with timing thought to be associated with global warming. While similar changes have been observed in other places, like Ontario, he said it was interesting to see these changes occur in “highly remote, highly sensitive lakes”.

“Basically greenhouse warming doesn’t have a passport — it goes wherever it goes,” Smol said.

Michelutti said environmental changes in the region over the last century spurred the team to study these lakes, adding that over the past several decades, the rate of warming in the Andes has been two times the global average.

He said an increase in temperature has resulted in “very noticeable and dramatic ecological effects”, including vegetation shifts, changes in cloud dynamics and glacier retreat.

“Many of these glaciers are predicted to disappear within the next 50 years. Some of these big ones that have stood for thousands of years are already completely gone,” Michelutti said.

Michelutti added that evidence of thermo stratification in the Ecuadorian lakes — a process whereby different layers form in a lake, with less dense, warmer ones located on top of colder layers — was inferred from the lakes’ algae.

“What we think that we’re seeing in these lakes now, is with this change in algae, we’re seeing algae that prefer to stay in the stratified – this thermally stratified water column,” he said.

“So as it warms up, the surface waters of these lakes are warming, they’re beginning to stratify, and that’s changing the algae.”

Since algae are located at the bottom of the food chain, Michelutti said this change has implications for other organisms like zooplankton — which feed on the algae — and fish.

“If lake is stratifying more, the lake is not as easily mixed. So these nutrient rich bottom waters don’t get brought up into the surface,” he said.

“So then you have less food for the algae, then there’s less for the zooplankton … which means then they’re less food for the fish.”

With plans to return to Ecuador this summer, Michelutti said his team will remove “temperature probes” they set up in lakes last summer and take more “core” samples in an attempt to look back further than the approximately 200 years examined in the published study.

“The lakes in the area are about 12,000 years old,” he said.

“If we got long enough cores, we could say just how unprecedented these changes are or if there have been similar-type changes in the past.”


Climate change, Research

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