1 million-year-old DNA suggests ‘productive’ future for melted Antarctica

Earth, traditionally a planet known for having ice caps at each pole, is quickly shaking its frigid reputation as its snowiest regions warm beyond recognition. This makes predicting the increasingly imminent effects of global warming a top priority for scientists seeking to understand the planet’s future – and nowhere is this more important than down at the white tip of the planet, Antarctica.

“Antarctica is arguably the most sensitive polar region to climate,” notes a paper published in the journal Nature Communications. “West Antarctica has warmed 2.4 ± 1.2°C [4.3 ± 2.2°F] between 1958 and 2010, making it one of the most warming regions globally.”

And to understand what this means for our planet’s southernmost continent, the researchers behind the study – an international team led by teams from Germany and Australia – turned to the past. Way, way in the past, actually. Using a new technique known as sedimentary ancient DNA analysis (sedaDNA), they have just discovered the oldest marine DNA on record – and it was hiding in the deep sea sediments of the Scotia Sea, just north of Antarctica.

“This includes by far the oldest certified marine sedaDNA to date,” Dr Linda Armbrecht, lead researcher from the University of Tasmania, Australia, said in a statement about the study. Indeed, at over 1 million years old, the DNA is about as old as the two previous record holders combined: ~400,000-year-old cave sediments discovered in 2003 and ~650,000-year-old permafrost deposits from Siberia studied earlier this year .

But as nice as that is, it’s not necessarily the most important result of the study itself. That title goes to a much younger contender: the half-million-year-old remains of diatoms, a type of phytoplankton that lived in the area during one of its warmest periods.

In fact, these phytoplankton were found in abundance throughout the time scale: “maximum abundance of diatoms [was confirmed] between 12.7 and 11.3 [thousand years] … that is, during the Antarctic Cold Reversal of the last glaciation termination,” the authors write.

What the researchers found was a radical change in the prehistoric marine ecosystem, coinciding with earlier periods of sudden warming. The proportion of diatoms among eukaryotes—organisms with membrane-bound nuclei—jumped from one in 10 to one in two during the last warming period 14,500 years ago, apparently causing a sharp increase in ocean productivity around Antarctica.

“This is an interesting and important change,” noted Dr. Michael Weber, a paleoceanographer at the University of Bonn, Germany, and second author of the study. “[It] linked to a global and rapid rise in sea level and massive ice loss in Antarctica due to natural warming.”

The success of the study is proof that techniques like sedaDNA – relatively new and unproven ways of investigating the biological world around us – can be viable tools over vast timescales, opening up a whole range of applications for paleoceanographers and climate researchers.

“Because the genetic traces of all organisms, fossil and soft-bodied, can potentially be preserved in sediment records, sedaDNA analysis has enormous potential to go beyond standard environmental markers and enable the reconstruction of entire ecosystems,” the authors write. “However, the recovery of sedaDNA is complicated, as only traces of DNA are preserved and fragmented and degraded, which makes sedaDNA susceptible to contamination by modern environmental DNA.”

But now, the doors are wide open. “Our find[s] … are important for paleoecology as they extend the time window of application of sedaDNA analyzes as a marine paleoenvironmental monitoring tool from ~140[thousand years]in ~ 1[million years]that is, spanning multiple glacial-interglacial cycles,” they explain.

After all, environmental DNA analysis – of which sedaDNA analysis is an example – has already proven its revelatory chops in the field of pandemic protection and endangered species conservation. Global warming, and the post-ice world we may soon be living in, is perhaps a natural next step in this impressive resume.

The study is published in the journal Nature Communications.

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