On Ardley Island in the Antarctic, a colony of gentoo penguins lives dangerously close to a volcano: the penguins have been brought to the brink of extinction several times over the past 7,000 years by volcanic eruptions. This is shown by a recent study in which Oldenburg researchers were involved.
Toxic volcanic ash buries penguin chicks and drives adult animals away. Hardly any nesting opportunities for subsequent breeding pairs: this or similar was the fate of gentoo penguins on Ardley Island in the Antarctic in the past when the volcano on nearby Deception Island erupted.
A good 5,000 pairs of gentoo penguins (Pygoscelis papua) live on the small island off the West Antarctic Peninsula. They form one of the largest colonies of this species in the Antarctic. Together with British experts, marine scientists from the Institute of Chemistry and Biology of the Marine Environment (ICBM) at the University of Oldenburg have reconstructed the fate that befell the penguin colony over the past 7,000 years. Their main evidence: penguin guano and volcanic ash dating back thousands of years. The discovery site: the deposits at the bottom of a small lake on Ardley Island.
These lake sediments form the historical memory of the region. Substances from the surrounding area accumulate here - such as penguin faeces and ash from volcanic eruptions. Based on the findings in the sediments, the Oldenburg scientists Dr Patrick Monien, Prof Dr Hans-Jürgen Brumsack, Dr Bernhard Schnetger and Julia Loftfield, together with researchers from the British Antarctic Survey in Cambridge and other colleagues, were able to find out how long penguins have existed in this region and how environmental changes have affected the population over the past 9,000 years.
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The results, now published in the journal "Nature Communications", turned out differently than the researchers had expected: "We assumed that changes in climate and sea ice cover would have the greatest impact on penguin numbers. But to our great surprise, this was not always the case in the past," says Monien. It is true that the population peak around 4,000 to 3,000 years ago coincided with a phase of warmer climate. But in the past 7,000 years, huge eruptions from the nearby volcano had a much greater impact on the penguins, adds the environmental scientist, who is now a researcher at the University of Bremen.
Among other things, the researchers used modern methods to analyse so-called "bio-elements", which are mainly found in penguin guano: High concentrations of these elements in the lake sediments indicate the presence of many penguins. If these elements are missing, this indicates a collapse of the penguin population. "We found that at least three volcanic eruptions, whose ash layers we were able to detect, during the middle Holocene, i.e. 7,000 to 4,000 years ago, caused the penguins on the island to almost disappear," says Monien. It would have taken around 400 to 800 years for the population to recover from these catastrophic events.
The project was initiated by ICBM researcher Brumsack, who specialises in the analysis of sediments. The geochemist emphasises that the investigation involved considerable logistical effort. However, the success shows how important international co-operation between scientists from different institutions is.