The Earth, traditionally a planet known for having ice caps at either pole, is quickly shaking its cold reputation, as its snowiest regions heat up beyond recognition. That makes predicting the increasingly imminent results of global warming a top priority for scientists seeking to understand the future of the planet – and nowhere is that more important than down at the lily-white butt of the planet, Antarctica.
“Antarctica is arguably the most susceptible polar region to climate,” points out 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 fastest-warming regions globally.”
And to figure out what that means for our planet’s most southerly continent, the researchers behind the study – an international group led by teams from Germany and Australia – have turned to the past. Way, way in the past, in fact. Using a new technique known as sedimentary ancient DNA (sedaDNA) analysis, they’ve 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 comprises by far the oldest authenticated marine sedaDNA to date,” said Dr Linda Armbrecht, the lead investigator from the University of Tasmania, Australia, in a statement on the study. Indeed, at more than 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 which were studied earlier this year.
But as cool as that is, it’s not necessarily the most important result of the study itself. That title instead goes to a much younger contender: the half-million-year-old remains of diatoms, a type of phytoplankton that lived in the area back when it was going through one of its warmer periods.
In fact, these phytoplankton were found in abundance across the timescale: “peak abundance of diatoms [was confirmed] between 12.7 and 11.3 [thousand years]… i.e., during the Antarctic Cold Reversal of the last glacial termination,” the authors write.
What the researchers found was a radical shift in the prehistoric marine ecosystem, timed closely with previous periods of sudden warming. The proportion of diatoms among eukaryotes – organisms with membrane-bound nuclei – shot from one in 10 to one in two during the last warming period 14,500 years ago, and apparently caused a sharp increase in ocean productivity around Antarctica.
“This is an interesting and important change”, noted Dr Michael Weber, a paleoceanographer from the University of Bonn, Germany, and second author of the study. “[It] is associated with a world-wide and rapid increase in sea levels and massive loss of ice in Antarctica due to natural warming.”
The study’s success is evidence that techniques such as sedaDNA – relatively new and unproven ways of surveying the biological world around us – can be viable tools over huge timescales, opening up a whole range of applications for paleoceanographers and climate researchers.
“Because genetic traces of all organisms, fossilizing and soft-bodied, can potentially be preserved in sediment records, the analysis of sedaDNA holds enormous potential to go beyond standard environmental proxies and allow reconstruction of entire ecosystems,” the authors write. “Yet, the recovery of sedaDNA is complicated, as only trace-amounts of DNA are preserved and they are fragmented and degraded, which makes sedaDNA prone to contamination from modern environmental DNA.”
But now, the doors are wide open. “Our finding[s] … are significant for paleoecology, as they expand the temporal window of applying sedaDNA analyses as a marine paleo-environmental monitoring tool from ~140 [thousand years] to ~1 [million years], i.e., covering multiple glacial-interglacial cycles,” they explain.
After all, environmental DNA analysis – of which sedaDNA analysis is one example – has already proven its apocalyptic chops in the realm 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 on that impressive résumé.
The study is published in the journal Nature Communications.