Lake Mendota in Wisconsin is transformed by the changing seasons – covered by ice in winter, and by algae in summer – and a new study shows how these cyclical shifts are putting the lake's bacteria into evolutionary loops.

Lake Mendota in Wisconsin is transformed by the changing seasons – covered by ice in winter, and by algae in summer – and a new study shows how these cyclical shifts are putting the lake’s bacteria into evolutionary loops.

Led by researchers from the University of Texas at Austin, the team behind the study analyzed 471 lake microbe samples collected across 20 years, looking at genetic variations within and between species through time.

The data showed thousands of bacteria species evolving through the generations, then evolving back to a virtually identical state as the seasons shifted. As microbes live just a few days, we’re talking about genetic evolution crossing thousands of generations within the span of one year.