Ancient DNA has unlocked the secrets of modern humans and their ancestors and is now helping focus research on Antarctica’s Adélie penguins.
An international team has extracted ancient DNA, known as sedaDNA, from Antarctic sediments, uncovering a 6,000-year history of Adélie penguin colonies along the Ross Sea coast.
The groundbreaking findings, published in Nature Communications, offer new insights into the presence of other local species, changes in population size—including a continued increase in Adélie penguin numbers in the region—shifts in diet, and their resilience. These revelations could play a pivotal role in informing future conservation strategies.
Researchers constructed a timeline of Adélie penguin habitation using radiocarbon dating, which measures the decay of carbon-14 in organic materials.
“We started digging down through the layers, and as you go down, you’re going back through time,” says lead author Dr Jamie Wood, a terrestrial ecologist and ancient DNA specialist from the University of Adelaide’s School of Biological Sciences and Environment Institute.
“In each of those layers we collected little fragments of penguin eggshell, and we were able to radiocarbon date those which gave us the ages of when each of those colonies was occupied by penguins”.
The team then used metagenomic sequencing on 156 sediment samples to analyse the DNA.
“The really useful thing from our study was how we demonstrated exactly what sort of detailed information you can get using sedaDNA.”.
Unlike previous studies, which have primarily used sedaDNA to identify species present at a given time, this study explored its use to track population changes and diet.
“SedaDNA is a rapidly growing field of research and is providing insights into past species and ecosystems at an unprecedented level of detail.
“We can see not just whether Adélie penguin DNA is present, but the diversity that’s present in that DNA can give you an indication of population size, as well as diet.
“Because these were terrestrial sediments, any fish DNA or krill DNA we picked up, we could infer was coming from the penguins eating them, and so we’re able to use it to track their dietary changes through time.”
The study revealed a surprising shift in the Adélie penguin diet. While today they predominantly feed on Antarctic silverfish in the southern Ross Sea, about 4,000 years ago, their primary prey was the bald notothen, a cryopelagic fish that thrives in the coldest waters of the Southern Ocean.
“Populations [of the bald notothen] appear to have declined in the southern Ross Sea, likely due to changing sea ice conditions, which led to a change in the Adélie penguin diet,” says Wood.
The findings from this study have the potential to inform future conservation policy in the Antarctic. “It can give us perhaps a better understanding of what the optimal food is for these birds. If we see them changing from one fish species to another, does that coincide with a drop in population size or an increase in population size?”
Evolutionary biologist Dr Theresa Cole, co-author of the study, says these long-term biological records are important.
“They give us important insights into how species respond to environmental and climatic conditions that may not have been experienced in recent times,” she says.
“Understanding the resilience of species to these natural environmental and climatic perturbations gives us a better ability to predict how they might respond to future challenges.”
What’s happening to the Adélie penguins?
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