Ancient DNA reveals how long fish have been living in our lakes

Researchers at the Department of Ecology and Environmental Science at Umeå University have recently found that fish DNA binds to lake sediment, forming a natural archive that can reveal when certain fish species colonized lakes after the glacial period.

For this study, the research team chose Lake Stora Lögdasjön and Lake Hotagen – which are in Sweden, in case the names didn’t tip you off enough. The reason behind these choices was that these lakes were known to have whitefish that colonized them at specific points in time. Stora Lögdasjön was connected to the Baltic Sea when the inland ice melted about 10,000 years ago. That connection was then cut off 9,200 years ago when the land lifted up and created a waterfall, which the whitefish were unable to travel up.

The researchers analyzed the prevalence of whitefish DNA in the sediment, finding that whitefish came to Stora Lögdasjön roughly 10,000 years ago, but they only arrived at Hotagen about 2,200 years ago.

“Our hypothesis was that the whitefish colonized Stora Lögdasjön immediately after the ice-melt, which turned out accurate. Close to Hotagen, on the other side, there was a waterfall that prevented the whitefish from colonizing the lake after the ice melted,” says Göran Englund, one of the researchers behind the study.

However, the DNA molecules that remain in the lake sediment are sparse. New methods of extraction had to be developed and difficult analyses took place in order for the data to be properly collected.

“Being able to map the prevalence of DNA in lake sediments is now opening up a new window into history, which lets us see how nature has developed over a long period of time,” says Göran Englund. “We have already started a project aiming to study how lake ecosystems are affected by historical climate changes. That can provide important clues to a better understanding of how the current global warming will affect ecosystems.”

The ability to look into the past using the technology of today is an important advancement that allows us to better understand the world around us. Studies such as this may initially seem trivial in their scope, but serve a greater purpose of furthering our knowledge of new research techniques that could benefit scientists around the world.

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By Connor Ertz, Earth.com Staff Writer