CANBERRA, March 5 (Xinhua) -- The study of ancient DNA preserved in sediment has revealed 6,000 years of history for Adelie penguin colonies along Antarctica's Ross Sea coast, shedding light on how these birds adapted to climatic and environmental shifts over thousands of years.

The research published in Nature Communications on Wednesday by an international team involved metagenomic sequencing of 156 sediment samples, provided valuable insights into Adelie penguins and the various species they encountered.

"Ancient sedimentary DNA recovered from Adelie penguin colonies allowed us to detect the presence of other local species through time, including a range of birds, seals and invertebrates," said lead author Jamie Wood, a terrestrial ecologist and ancient DNA specialist from the University of Adelaide.

The researchers found that although the Antarctic silverfish is now the primary fish consumed by Adelie penguins, it was not always their main prey.

They reported that around 4,000 years ago, the bald notothen, a cryopelagic fish, was an important part of the penguins' diet. However, its population appears to have declined in the southern Ross Sea, likely due to changes in sea ice conditions, which subsequently led to a shift in the penguins' feeding habits.

The analysis of sedimentary ancient DNA (sedaDNA) also identified the presence of southern elephant seals.

The study's joint lead author, Zhou Chengran of BGI Research, based in central China's Wuhan, said discovering evidence of a possible past breeding colony of southern elephant seals at Cape Hallett on the Ross Sea coast was entirely unexpected.

"Although these seals no longer breed on the Antarctic mainland, we now have evidence to indicate they once did more than 1,000 years ago," Zhou said.

Before discovering southern elephant seal DNA in the sediments, there had been no prior evidence of their presence at Cape Hallett, Zhou said, adding this finding makes Cape Hallett the northernmost known former breeding site in the Ross Sea region.

"Looking at biological records that span thousands of years gives us important insights into how species respond to environmental and climatic conditions that may not have been experienced in recent times," said study co-author Theresa Cole from the University of Adelaide.

Understanding how species have adapted to natural environmental and climatic changes in the past helps improve predictions about how they might react to future challenges, Cole said.

Technological developments mean new discoveries will continue to be made using sedaDNA, which is a rapidly growing field of research and is providing insights into past species and ecosystems at an unprecedented level of detail, according to Wood. Enditem

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