Paleoenvironmental insights into ice-ocean interactions in East Antarctica

As meso-order predators, snow petrels (Pagodroma nivea) play a significant role in the Antarctic food web. Changes in their abundance can be related to the availability of prey and thus provide an indication of ecosystem health. The foraging grounds of snow petrels lie within the pack ice and open waters of the Southern Ocean, while their nesting sites are restricted to ice-free areas on the Antarctic mainland and surrounding islands. Modern observations of the birds allow conclusions to be drawn about their breeding performance and foraging ecology in relation to environmental parameters, such as sea-ice extent. Biological studies on the distribution of nesting sites and the response of the birds to changing environmental conditions can be complemented by the analysis of fossil stomach oil deposits produced by snow petrels, the so-called 'Antarctic mumiyo'. Stomach oil is composed of lipid-rich dietary components and can therefore provide information on the composition of the diet, which consists mainly of different fish and krill species.

Fossil stomach oil deposits provide information on the timing of snow petrel occupation of a particular nesting site and can be used as an indicator of ice sheet retreat. However, 'Antarctic mumiyo' also serves as a novel terrestrial archive for paleoenvironmental reconstructions in the Southern Ocean. Analyses of the organic and inorganic composition of the stomach oil deposits allow assumptions to be made about the paleodiet of the snow petrels, which in turn depends on the oceanic environmental conditions prevailing at the time of deposition. We investigate stomach oil deposits from several coastal sites in East Antarctica (including the Vestfjella, Framnes Mountains, Bunger Hills, and Windmill Islands) to develop new proxies for the composition of the paleodiet and to link these to marine environmental conditions (e.g., sea-ice variability and polynya occurrence) during the Holocene.

The fossil stomach oil deposits are examined using inorganic, lipid, and isotopic geochemical methods, as well as radiocarbon dating for temporal constraints. Evidence for regional differences in the paleodiet comes from lipid data, such as n-C14 to n-C24 alcohol and fatty acid distributions, reflecting either a more fish or krill dominated paleodiet. We will present initial regional reconstructions based on ¹⁴C-dated stomach oil deposits from Bunger Hills and Framnes Mountains and discuss potential links between paleoenvironmental conditions and paleodiet.