Holocene variation in the Antarctic coastal food web: linking delta D and delta C-13 in snow petrel diet and marine sediments

Here we present first time evidence for concordant variation in the isotopic signature at both the base and the upper levels of the Antarctic coastal food web during the Holocene. Laminae in sub-fossil deposits of snow petrel Pagodroina nivea stomach oil, known as mumiyo, were collected from nest-sites in the Bunger Hills, East Antarctica. Mumiyo layers were sub-sampled, radiocarbondated, and analyzed for delta C-13 and delta D. The obtained values were compared to isotopic variability among layers of an ocean sediment core collected, and similarly dated, in nearby Dumont D'Urville Trough. Overlapping records extended from about 10 160 to 526 calendar years before present (cal yr BP). Mumiyo delta D values remained relatively constant throughout the sampled period, in accordance with data from nearby ice cores. For C-13, both mumiyo and sediment were enriched during the warmer midHolocene (ca. 7500 to 5500 cal yr BP). Isotopic concordance between the core and the mumiyo, and a significant correlation between mumiyo delta D and delta C-13, suggest that past delta C-13 variation in plankton was transferred through diet to higher trophic levels and ultimately recorded in stomach oil of snow petrels. Divergence in signals during cold periods may indicate a shift in foraging by the petrels from C-13-enriched neritic prey to normally C-13-depleted pelagic prey, except for those pelagic prey encountered at the productive pack-ice edge during cooler periods, a shift forced by presumed greater sea-ice concentration during those times. Other air-breathing predators would likely respond in the same way.