PEARL

December 16, 2008

Northern hemisphere lakes have crossed important ecological thresholds, say Queen’s scientists

Kingston, ON – Unparalleled warming over the last few decades has triggered widespread ecosystem changes in many temperate North American and Western European lakes, say researchers at Queen’s University and the Ontario Ministry of the Environment.

The team reports that striking changes are now occurring in many temperate lakes similar to those previously observed in the rapidly warming Arctic, although typically many decades later. The Arctic has long been considered a “bellwether” of what will eventually happen with warmer conditions farther south. 

“Our findings suggest that ecologically important changes are already under way in temperate lakes,” says Queen’s Biology research scientist, Dr. Kathleen Rühland, from the university’s Paleoecological Environmental Assessment and Research Lab (PEARL) and lead author of the study.  

The research was recently published in the international journal Global Change Biology. Also on the team are Biology professor John Smol, Canada Research Chair in Environmental Change, and Andrew Paterson, a research scientist at the Ontario Ministry of the Environment and an adjunct professor at Queen’s.

One of the biggest challenges with environmental studies is the lack of long-term monitoring data, Dr. Rühland notes. “We have almost no monitoring data on how lakes have responded to climate change over the last few decades, and certainly no data on longer term time scales,” she says. “However, lake sediments archive an important record of past ecosystem changes by the fossils preserved in mud profiles.”

The scientists studied changes over the last two centuries in the species composition of small, microscopic algae preserved in sediments from more than 200 lake systems in the northern hemisphere. These algae dominate the plankton that float at or near the surface of lakes, and serve as food for other larger organisms. 

Striking ecosystem changes were recorded from a large suite of lakes from Arctic, alpine and temperate ecozones in North America and western Europe.  Aquatic ecosystem changes across the circumpolar Arctic were found to occur in the late-19^th and early 20^th centuries. These were similar to shifts in algal communities, indicating decreased ice cover and related changes, over the last few decades in the temperate lakes.

“As expected, these changes occurred earlier – by about 100 years – in highly sensitive Arctic lakes, compared with temperate regions,” says Dr. Smol, recipient of the 2004 Herzberg Gold Medal as Canada’s top scientist.

In a detailed study from Whitefish Bay, Lake of the Woods, located in northwestern Ontario, strong relationships were found between changes in the lake algae and long-term changes in air temperature and ice-out records. The authors believe that, although the study was focused on algae preserved in lake sediments, changes to other parts of the aquatic ecosystem are also likely (for example algal blooms and deep-water oxygen levels).

“The widespread occurrence of these trends is particularly troubling as they suggest that climatically-induced ecological thresholds have already been crossed, even with temperature increases that are below projected future warming scenarios for these regions,” adds Dr. Paterson. The authors warn that if the rate and magnitude of temperature increases continue, it is likely that new ecological thresholds will be surpassed, many of which may be unexpected.

“We are entering unchartered territory, the effects of which can cascade throughout the entire ecosystem,” concludes Dr. Smol.

The research was funded by the Natural Sciences and Engineering Research Council of Canada, and the Ontario Ministry of the Environment.

Contacts: 

Nancy Dorrance, Queen’s News & Media Services, 613.533.2869

Molly Kehoe, Queen’s News & Media Services, 613.533.2877

Attention broadcasters:  Queen’s has facilities to provide broadcast quality audio and video feeds. For television interviews, we can provide a live, real-time double ender from Kingston fibre optic cable. Please call for details.

PLEASE NOTE: A PDF copy of the study can be obtained from the journal Global Change Biology, or contact Dr. John Smol at smolj@queensu.ca for a copy. High resolution images are available upon request.

Contacts:

Nancy Dorrance, Queen’s News & Media Services, 613.533.2869

Molly Kehoe, Queen’s News & Media Services, 613.533.2877

Attention broadcasters:  Queen’s has facilities to provide broadcast quality audio and video feeds. For television interviews, we can provide a live, real-time double ender from Kingston fiber optic cable. Please call for details.