UNCW Researcher Discovers Abandoned 'Supercolony' of Adélie Penguins in Antarctica

Antarctica's most populous colony of Adélie penguins once may have been nearly twice the size it is today, UNCW biology and marine biology professor Steven D. Emslie and his research team discovered on a recent trip to the continent. Clues about why the colony grew so large and what has since caused a population decline could help scientists chart the penguins' response to changes in climate and food resources.

During a mid-January research excursion to Cape Adare in the northern Ross Sea, Emslie found evidence that the colony, which consists of more than 338,000 breeding pairs on a lower terrace, had once also covered the vast and now abandoned upper terrace. As large as that number sounds, Emslie conservatively estimates the former "supercolony" at Cape Adare once included more than 500,000 breeding pairs, or more than 1 million penguins.

His assessment, based on an examination of abandoned nesting sites, stems from collaborative research conducted by UNCW, Louisiana State University and the University of California at Santa Cruz under grants from the National Science Foundation totaling nearly $1.28 million. The University of Saskatchewan also is a participant in the research.

Emslie hypothesizes there may have been a huge influx of penguins to the colony at Cape Adare beginning about 2,000 years ago, followed by a decrease to its current number. The penguins apparently abandoned a large part of their southern Ross Sea area breeding ground, possibly forced north to Cape Adare as a climate shift caused ice to block access to the beach for nesting. As the Cape Adare colony grew, the nesting grounds expanded to the upper terrace but later shrunk to its current size. A supercolony would thrive only as long as rich food resources were available.

"Many seabirds have large breeding colonies today that are located near abundant food resources," Emslie said. "Most of those colonies are in decline, though, due to changing ocean temperatures and other factors that impact those food resources." Human impacts on the marine environment over the past century are one of many factors for the decline in seabird species today, he said.

Emslie's research partner at LSU, Michael Polito '01, '12 Ph.D., is an assistant professor of oceanography and coastal sciences and principal investigator for the overall project. UNCW graduate student Ashley McKenzie also helped collect samples on this trip.

"The goal of this multi-institutional collaborative project is to use penguins as sensitive indicators of past changes in the Antarctic marine environment," Polito said. "Samples from this newly discovered ancient colony at Cape Adare will allow us to track the penguins' diets and population movements relative to natural and human-induced shifts in climate and food availability."

Analyzing that information will allow scientists to better understand how these penguins and the ecosystems on which they depend will respond to contemporary challenges such as global warming and expanded commercial fishing, Emslie and Polito explained.

The site at Cape Adare is now the largest Adélie penguin colony documented in the paleo record. The team will use radiocarbon dating to pinpoint the age of the nests and stable isotope analysis to determine the penguins' diets at the time the upper-terrace colony was active.

The continent's frigid climate is ideal for researching the progress of species over tens of thousands of years, Emslie explained. "Only in Antarctica do you find the long-term preservation of tissues in soil - frozen in time - that provide so much information about living species in the same place where they still occur today."

Adélie penguins have been present in the same part of Antarctica for more than 45,000 years.

Emslie has kept a blog of his trips to Antarctica, as well as photos and a video showing the remnants of the supercolony at Cape Adare.

-- Tricia Vance