As we are a species with an ever-shrinking attention span, it can be difficult to comprehend how long life has existed on Earth. Try to wrap your mind around it, though: Scientists have dug up DNA fragments dating back 1 million years.
Found beneath the floor of the Scotia Sea, north of Antarctica, these fragments of organic material can be invaluable in mapping the history of the region – mapping out what has lived in the ocean and over what kind of timescales.
Technically referred to as sedaDNA – for sedimentary ancient DNA – the recovered samples are likely to prove useful in ongoing efforts to understand how climate change could affect Antarctica in the future.
“This includes by far the oldest certified navy sedaDNA to date,” says marine ecologist Linda Armbrecht from the University of Tasmania in Australia.
SedaDNA is found in many environments, including terrestrial caves and subarctic permafrost, which have yielded sedaDNA dating back 400,000 and 650,000 years, respectively.
The cold temperatures, low oxygen and lack of UV radiation make polar marine environments such as the Scotia Sea excellent locations for sedaThe DNA remains intact, just waiting to be found.
The recovered DNA was extracted from the ocean floor in 2019 and went through a comprehensive contamination control process to ensure the age markers embedded in the material were accurate.
Among other findings, the team discovered diatoms (single-celled organisms) dating back 540,000 years. All of this helps inform our overview of how this part of the world has evolved over vast stretches of time.
The team was able to link the abundance of diatoms to warmer periods – the last of which in the Scotia Sea was around 14,500 years ago. This has led to an increase in overall marine life activity throughout the Antarctic region.
“This is an interesting and important change associated with a global and rapid rise in sea level and massive ice loss in Antarctica due to natural warming,” says geologist Michael Weber from the University of Bonn in Germany.
This latest study is proof that these sedaDNA techniques can help reconstruct ecosystems over hundreds of thousands of years, giving us a whole new level of insight into how the oceans have changed.
Scientists are steadily getting better at removing these ancient DNA fragments from the soil and removing the “noise” and interference left by all the modern DNA that’s been around since then to get an authentic look at the past.
Understanding more about past climate changes and how the ocean ecosystem responded means more accurate models and predictions of what might happen next around the South Pole.
“Antarctica is one of the most vulnerable regions to climate change on Earth, and studying the past and present responses of this polar marine ecosystem to environmental change is urgent,” the researchers write in their published paper.
The research has been published in Nature communications.