The study, led by Warwick Vincent and Reinhard Pienitz of Laval University's Center for Northern Studies, focused on Ward Hunt Lake, located on a small Canadian Arctic island.

The researchers discovered major transformations of the lake's aquatic life within the last two centuries. The speed and range of the transformations suggest climate change caused the phenomenon.

The researchers analyzed a seven-inch-long sediment core extracted from the lake in 2003, containing algae pigments and diatom remnants.

Analysis of the deepest layers of sediment revealed a very small number of algae as well as only minor variations in concentration. However, the top inch, corresponding to the last 200 years, showed abrupt changes in the lake’s algae population and the first appearance of a type of diatom typical of very cold environments.

"The absence of diatoms and the low pigment concentration below the top 2.5 centimeters of the core suggest that the lake was permanently frozen in the past," said lead author Dermot Antoniades.

The study, which included scientists from the United States and New Zealand, is reported in Geophysical Research Letters.