The discovery of the oldest marine DNA dating back a million years to an organism that lived in the depths of Antarctica

Organisms leave their DNA behind in the environment in which they live. Is it possible to trace the DNA to the organisms that inhabited the deep oceans a million years ago?

A recent study led by researchers from the Australian University of Tasmania in cooperation with the University of Bonn in Germany revealed - and published in the journal Nature Communications on October 2 - Reveals a million-year-old DNA, preserved in the sediments of the Scotia Sea deep in northern Antarctica.

This eukaryotic DNA is the oldest marine DNA in the world ever discovered. So this discovery will pave the way for long-term effects on ocean ecosystems.

Antarctica is one of the most vulnerable regions to climate change on Earth. Therefore, studying how these polar ecosystems respond to environmental and climate change is crucial.

According to the press release published by the University of Bonn, the technique of analyzing the sedimentary DNA of ancient organisms - known for short as "sedaDNA" - helps scientists decipher the organisms that lived in ancient oceans, as well as enabling them to know when they were living It contains these objects.

Knowing when major changes occur may contribute to understanding climate change, and thus help us make predictions about how marine life in Antarctica will respond to current and future climate changes.

In good condition

And DNA is not found inside the body of a living organism only, but what it leaves behind, whether it is layers of dead skin, urine, feces, saliva, or the remains of decomposing organisms, all carry the fingerprints of DNA. So the DNA of organisms can be found in the air, in the soil and in deep-sea sediments, so analysis of DNA samples can provide us with information about what organisms lived in the environment from which these samples were collected.

However, the polar deep-sea sediment samples have an added advantage. Due to the low temperatures in these regions, the DNA samples remain well preserved for long periods. The low level of oxygen and the distance from harmful ultraviolet rays protect these samples from damage and reactions that may change the structure of DNA.

The researchers used the technique of sedimentary DNA analysis of ancient organisms to study the changes in the structures of marine organisms in the Scotia Sea over the past million years, using sediments collected by previous expeditions in 2019.

The researchers first checked the quality of the samples, including checking for age-related forms of damage that might have been inflicted on the recovered DNA samples. This eventually enabled them to obtain a marine DNA sample that was estimated to be 750,000 to 1 million years old.

Various samples

The researchers' analyzes also revealed the presence of approximately 300,000 DNA fragments in these sediments belonging to bacteria, archaea and eukaryotes. "These samples are the oldest documented ancient sedimentary DNA samples to date," said Linda Armbrecht, lead researcher on the study from the University of Tasmania.

In addition, scientists have discovered the DNA of some other marine organisms such as diatoms (a large group of algae and is one of the most famous types of phytoplankton), which dates back to half a million years ago. This is also the oldest evidence of genetic material for this group of algae in marine sediments.

The results also indicated that diatoms were abundant during warm climatic periods. The last change in the Scotia Sea food web occurred about 14,500 years ago.

About this change in the food web, Michael Webber, one of the study's co-authors, says it is an "exciting and important change associated with the rapid global increase in sea levels. It appears that increased warming has contributed to the increase in the productivity of the oceans around Antarctica."

This study confirms that the technique of analyzing the sedimentary DNA of ancient organisms may provide us with information about organisms dating back hundreds of thousands of years, which may help researchers to study the transformations of marine ecosystems, and to know the impact of current and future global warming on ecosystems