Dynamics of penguin population size and food availability at Prydz Bay, East Antarctica, during the last millennium: A solar control

Abstract

The paleoecology of the Adélie penguin (Pygoscelis adeliae) is controlled by multiple factors. In this study, we analyzed two millennial-scale ornithogenic sediment cores, RNL and RL, from the Vestfold Hills, East Antarctica. Using the Al-normalized phosphorus content of the bulk sediment and carbon/nitrogen fractions in penguin remains, we reconstructed relative changes in the penguin population size of each sub-colony and relative krill abundance in the summer Prydz Bay polynya. Both records are correlated to solar irradiance. At the centennial scale, the penguin population recorded in core RNL decreased from ~1120–860 yr BP, reached a peak from ~860–630 yr BP, remained at a low level from ~630–320 yr BP, and then increased with large fluctuations during the past ~400 years. These changes are all in-phase with the trend of solar irradiance. At the decadal scale, penguin population minima correspond to solar minima from ~490–400 yr BP (Spörer minimum), ~290–220 yr BP (Maunder minimum), and from ~160–120 yr BP (Dalton minimum; whereas population maxima correspond to solar maxima from ~1030–980 yr BP, ~350–290 yr BP, ~210–160 yr BP, ~120–70 yr BP. The population recorded in core RL exhibited the same changes as in RNL during the last 480 years. The reconstructed krill abundance also corresponds to these trends when data are available. This correspondence demonstrates a food-chain mechanism that is related to solar activity and light availability at the ocean surface, which influence the intensity of photosynthesis and phytoplankton productivity, and thus the abundance of krill and apex predators such as penguins. Our findings highlight the fact that despite the various climatic impacts on penguin populations, their effects on the base of the food chain are usually the direct drive.