Penguin tissue as a proxy for relative krill abundance in East Antarctica during the Holocene

Antarctic krill (Euphausia superba) is a key component of the Southern Ocean food web. It supports a large number of upper trophic-level predators, and is also a major fishery resource. Understanding changes in krill abundance has long been a priority for research and conservation in the Southern Ocean. In this study, we performed stable isotope analyses on ancient Adelie penguin tissues and inferred relative krill abundance during the Holocene epoch from paleodiets of Adelie penguin (Pygoscelis adeliae), using inverse of delta N-15 (ratio of N-15/N-14) value as a proxy. We find that variations in krill abundance during the Holocene are in accord with episodes of regional climate changes, showing greater krill abundance in cold periods. Moreover, the low delta N-15 values found in modern Adelie penguins indicate relatively high krill availability, which supports the hypothesis of krill surplus in modern ages due to recent hunt for krill-eating seals and whales by humans.