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 Ruhland, 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. Ruhland notes. "We have almost no 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 few decades 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, a
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