Abrupt recent shift in δ13C and δ15N values in Adelie penguin eggshell in Antarctica

Stable isotope values of carbon (delta C-13) and nitrogen (delta N-15) in blood, feathers, eggshell, and bone have been used in seabird studies since the 1980s, providing a valuable source of information on diet, foraging patterns, and migratory behavior in these birds. These techniques can also be applied to fossil material when preservation of bone and other tissues is sufficient. Excavations of abandoned Adelie penguin (Pygoscelis adeliae) colonies in Antarctica often provide well preserved remains of bone, feathers, and eggshell dating from hundreds to thousands of years B.P. Herein we present an approximate to 38,000-year time series of delta C-13 and delta N-15 values of Adelie penguin eggshell from abandoned colonies located in three major regions of Antarctica. Results indicate an abrupt shift to lower-trophic prey in penguin diets within the past approximate to 200 years. We posit that penguins only recently began to rely on krill as a major portion of their diet, in conjunction with the removal of baleen whales and krill-eating seals during the historic whaling era. Our results support the krill surplus hypothesis that predicts excess krill availability in the Southern Ocean after this period of exploitation.