Climate Change

A million-year-old marine DNA can reveal how climate change will affect Antarctica

New form of analysis helps scientists study long-term responses of ocean ecosystems

By Nandita Banerji
Published: Monday 10 October 2022
The DNA fragments were taken from the Scotia Sea, north of the Antarctic continent. Photo: Thomas Ronge / Alfred-Wegener-Institute__

Scientists have dug up fragments of deoxyribonucleic acid, also known as DNA, in the Scotia Sea, north of the Antarctic continent. The DNA is a million years old and makes it possible to study the responses of ocean ecosystems to climate change. 

A study, conducted by researchers from University of Tasmania and University of Bonn discovered ancient sedimentary DNA (sedaDNA). 

SedaDNA analysis is a new technique that helps decipher ‘who’ has lived in the ocean in the past and ‘when’. It can help study long-term responses of ocean ecosystems to climate change, as demonstrated by the study Ancient marine sediment DNA reveals diatom transition in Antarctica

Read more: Ice flow in Antarctica changes with season, can impact sea-level rise estimates

The study, which was published in the journal Nature Communications, can also help assess current and future changes in marine life around Antarctica

Antarctica is one of the most vulnerable regions to climate change on Earth, so studying the frozen continent’s past and present responses to environmental and climate change is therefore critical and urgent.

Antarctica is arguably the most susceptible polar region to climate, evidenced in the fact that west Antarctica is one of the fastest-warming regions globally, the study said. 

Understanding how southern Ocean organisms respond to climate variability, including throughout past climate shifts, is thus of key importance to predict how the Antarctic marine ecosystem will evolve in the near future, the study added. 

An international team studied sediments acquired during the International Ocean Discovery Program, an international, multi-drilling platform research program. The samples were collected in 2019 expedition 382, called Iceberg Alley and Subantarctic Ice and Ocean Dynamics. 

Investigation of characteristic age-related damage patterns in the recovered DNA fragments revealed they were as old as a million years. 

“This comprises by far the oldest authenticated marine sedaDNA to date,” said Linda Armbrecht, the lead investigator from the University of Tasmania, Australia. 

Amongst the detected organisms were diatoms as key primary producers whose DNA was detected back to half a million years.

Diatoms were consistently abundant during warm climatic periods, showed data collected by the researchers. The last such change in the food web of the Scotia Sea occurred about 14,500 years ago. 

Read more: Increasing human footprint cutting Antarctica wilderness: Study

“This is an interesting and important change that is associated with a word-wide and rapid increase in sea levels and massive loss of ice in Antarctica due to natural warming,” said Michael Weber, second author of the study from the University of Bonn. 

The warming apparently caused an increase in ocean productivity around Antarctica.

The study demonstrates that marine sedaDNA analyses can be expanded to hundreds of thousands of years, opening the pathway to the study of ecosystem-wide marine shifts and changes to paleo-productivity throughout many ice-age cycles. 

These periods of natural climate change can also give insight into the current and future human-induced climate warming and how the ecosystem might respond to it.

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