Researchers find 1 million-year-old marine DNA in Antarctic sediments

A new study led by the University of Tasmania – with participation from the University of Bonn – discovered the oldest marine DNA in deep-sea sediments of the Scotia Sea north of the Antarctic continent. The material has been dated to a million years. Such ancient material shows that sedimentary DNA can pave the way to study long-term responses of marine ecosystems to climate change. This recognition will also help assess current and future changes in marine life around the frozen continent. The study was published in the journal nature communication.

Antarctica is one of the regions on earth most affected by climate change. Studying the past and present responses of the polar marine ecosystem to environmental and climate change is therefore critical and urgent. Analysis of ancient sedimentary DNA (sedaDNA) is a new technique that can be used to decipher “who” lived in the ocean in the past and “when”. Times of great changes in composition can also be related to climate change. This knowledge can help us make predictions about how marine life in Antarctica will respond to current and future climate change.

An international team used sedaDNA to study changes in the structures of marine organisms in the Scotia Sea over the past 1 million years, using sediments recovered during IODP Expedition 382 “Iceberg Alley and Subantarctic Ice and Ocean Dynamics” in the Purchased in 2019. First, the team carried out a comprehensive contamination by checking the authenticity of sedaDNA signals, including, for example, examining characteristic age-related damage patterns in the DNA fragments obtained. They were able to discover ancient DNA dating back up to a million years.

“This is by far the oldest authenticated sedaDNA from the sea to date,” said Dr. Linda Armbrecht, senior researcher at the University of Tasmania, Australia. Among the organisms detected were diatoms as important primary producers, whose DNA could be traced back to half a million years.

The data also show that diatoms have been consistently abundant during warm climate periods. The last such change in the Scottish Sea food web occurred about 14,500 years ago. “This is an interesting and important change that coincides with global and rapid sea level rise and massive ice loss in Antarctica due to natural warming,” added Dr. Michael Weber, co-author of the study from the University of Bonn. The warming apparently caused an increase in the productivity of the oceans around Antarctica.

The study shows that marine sedaDNA analyzes can be extended to hundreds of thousands of years, paving the way for the study of ecosystem-wide marine shifts and changes in paleoproductivity during many glacial cycles. These periods of natural climate change can also shed light on current and future human-caused global warming and how the ecosystem might respond.