Oldest marine DNA discovered in Antarctica
In the deep sea, and especially in the sediments, there are still countless secrets hidden. In the Antarctic seafloor in the Scotia Sea, an international research team has now discovered the oldest marine DNA, at one million years old. For the study of long-term responses of marine ecosystems to climate change, such ancient sedimentary DNA opens up entirely new possibilities. Present and future changes in marine life around Antarctica can thus be better assessed. The study was published in the journal Nature Communications.
Studying the past and present responses of the Antarctic marine ecosystem to environmental and climate change is critical because Antarctica is one of the regions most vulnerable to climate change. With the help of sedimentary ancient DNA (sedaDNA), the species composition can be deciphered and when the respective species lived in the ocean. This also allows linking drastic changes in species composition to climate changes in the past, which in turn helps in making predictions about the responses of present-day marine life to current and future climate change.
The international research team, including scientists from the University of Tasmania and the University of Bonn, collected sediment samples in the Scotia Sea in 2019 and used sedaDNA to study changes in the structure of marine organisms over the past one million years. After checking for contamination, the team was able to detect DNA that was up to one million years old. In the samples, they also identified DNA from diatoms – important primary producers in the ocean – that is 540,000 years old, and even eukaryotic DNA that appears to be 2.5 million years old.
“This comprises by far the oldest authenticated marine sedaDNA to date,” said Dr. Linda Armbrecht, lead author of the study from the University of Tasmania, Australia.
Using ancient sedaDNA, the researchers were also able to determine that diatoms were consistently abundant during warm climate periods. The last such change in the Scotia Sea food web occurred about 14,500 years ago. “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,” explains Dr. Michael Weber of the University of Bonn, co-author of the study. Warming apparently led to an increase in marine productivity around Antarctica.
According to the study, sedaDNA is found in many different environments, including terrestrial caves and Arctic permafrost, where the material dates back as far as 650,000 years. SedaDNA remains intact in places like the Scotia Sea for such along time because of low temperatures, low oxygen levels, and lack of UV radiation.
Julia Hager, PolarJournal
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