The finding at Kaffeklubben So lake on the coastal plain of northern Greenland is the latest evidence that climate change in polar regions can result in rapid ecological changes, they said.
The 120-acre lake looks out over the Arctic Sea.
"It's kind of the end of the earth," Bianca Perren of the University of Franche-Comte in France said.
The lake is covered with 3 to 6 feet of ice year-round, but a "moat" of water forms around the edge of the lake in summer when average temperatures rise to 35 degrees Fahrenheit, NewScientist.com reported.
When the lake formed about 3,500 years ago a few species of silica-shelled algae called diatoms lived in the young lake, but their populations declined as regional temperatures cooled, and they vanished entirely 2,400 years ago.
The lake remained nearly barren until around 1960 when the first diatom species returned, and the latest water samples collected by Perren and her colleagues contain some 20 species.
While nitrates and industrial pollutants may have encouraged the tiny organisms to bloom in other lakes, there are no traces of nitrates in Kaffeklubben, indicating its recolonization by diatoms was driven purely by climate change, Perren said.