Summer sea-ice variability on the Antarctic margin during the last glacial period reconstructed from snow petrel (Pagodroma nivea) stomach-oil deposits

Antarctic sea ice is a critical component of the climate system, affecting a range of physical and biogeochemical feedbacks, and supporting unique ecosystems. During the last glacial stage, Antarctic sea ice was more extensive than today, but uncertainties in geological (marine sediments), glaciological (ice core), and climate model reconstructions of past sea-ice extent continue to limit our understanding of its role in the Earth system. Here, we present a novel archive of past sea-ice environments from regurgitated stomach oils of snow petrels (Pagodroma nivea), preserved at nesting sites in Dronning Maud Land, Antarctica. We show that by combining information from fatty acid distributions and their stable carbon isotope ratios with measurements of bulk carbon and nitrogen stable isotopes and trace metal data, it is possible to reconstruct changing snow petrel diet within Marine Isotope Stage 2 (ca. 22.6–28.8 cal. kyr BP). We show that, as today, a mixed diet of krill and fish characterises much of the record. However, between 25.7–26.8 cal. kyr BP signals of krill almost disappear. By linking dietary signals in the stomach-oil deposits to modern feeding habits and foraging ranges, we infer the use by snow petrels of open water habitats (‘polynyas’) in the sea ice during our interval of study. The periods when consumption of krill was reduced are interpreted to correspond to the opening of polynyas over the continental shelf, which became the preferred foraging habitat. Our results challenge hypotheses that the development of extensive, thick, multi-year sea-ice close to the continent was a key driver of positive sea ice-climate feedbacks during glacial stages, and highlight the potential of stomach-oil deposits as a palaeo-environmental archive of Southern Ocean conditions.

Comparative egg attendance patterns of incubating polar petrels

Background The internal environment of eggs in most birds is regulated by transferring heat energy through contact incubation, maintaining nest microclimate, and frequent egg turning by the incubating parent on its nest. However, we lack information about egg attendance patterns in birds that breed in polar environments where variations in life history are expected to influence incubation behavior. Moreover, crevice/burrow nesting petrels in high-latitude regions are known for periodically leaving their egg unattended (hereafter ‘egg neglect’), but there is little reporting on the internal condition of unattended eggs. At Dumont d’Urville Station, Antarctica, we studied the incubation behavior of 24 snow (Pagodroma nivea) and 15 Cape (Daption capense) petrel pairs using egg loggers that recorded egg turning rates, orientation changes, and temperatures at 1 Hz for durations of 3–6 days. Results Egg turning frequency (1.31 ± 0.33 vs. 1.38 ± 0.39 turns h−1), angle change per turn (43.1 ± 43.2 vs. 48.6 ± 43.7° turn−1), and egg temperature (34.1 ± 2.3 vs. 34.1 ± 2.0 °C) were nearly identical for snow and Cape petrels, respectively. However, egg neglect was only observed in snow petrel nests (based on egg temperature changes) where loggers recorded mean durations of 1.34 ± 1.15 days (maximum duration of 3.63 days). During periods of neglect, eggs cooled to 5.5 ± 1.8 °C over an average of 91 min, but were rewarmed by parents in only 76 min at a rate of 0.33 °C min−1. Conclusions Egg temperatures of both species during regular incubation were within 1–2 °C of other high-latitude petrel species, but neglected snow petrel eggs remained several degrees above freezing, which was likely attributed to crevice nesting where neglected eggs are buffered by environmental conditions. Using egg rewarming rates, thermal capacity of eggs, and published metabolic rates, we estimate egg rewarming costs in snow petrels to be 1.5 to 1.9 × BMR. Excluding egg neglect periods, turning rates for both petrel species were lower than other seabirds studied using biologging devices, which may be associated with the prolonged incubation periods that are characteristic of procellariiform seabirds.

Very Low Density and Biodiversity of Seabird and Marine Mammal at-sea Distribution in the Amundsen Sea, 2010

Our long-term study on the quantitative at-sea distribution of the upper trophic levels - seabirds and marine mammals - in polar ecosystems aims at quantifying the factors influencing their distribution as well as detecting possible spatial and temporal changes, with special attention to hydrography and global climate changes. During the ANT- XXVI/3 expedition of icebreaking RV Polarstern in February-March 2010, a total of 8,270 seabirds belonging to 15 identified species were recorded in the Amundsen Sea during 1,070 half-hour transect counts, with a mean of eight birds per count. The most numerous species were by far Antarctic petrel, Adélie penguin and snow petrel, which together accounted for more than 80% of all individuals of these species recorded. Substantial hotspots of seabirds perched on three icebergs, representing 44% of all observations: 85% of the Antarctic petrels and 40% of the snow petrels [1]. Without taking into account these data, the mean seabird number becomes five individuals per count, representing the lowest value registered in Antarctic seas. The most numerous pinniped was crabeater seal contributing 98% of the total of 2,350 individuals of four pinniped species [2]. Among cetaceans, the most abundant species were Antarctic Minke whale and fin whale (60% and 25% of the total of 170 individuals, four species). The maps allow for a visual comparison that is sufficient for the purposes of this article, reflecting the influence of hydrological features such as water masses and fronts, pack ice and ice edge, free drifting icebergs.

Past records and current distribution of seabirds at Larsemann Hills and Schirmacher Oasis, east Antarctica

Seabird populations in Antarctica serve as indicators to assess the impacts of global environmental change. Ecological data on seabirds in Antarctica are scarce due to limited knowledge on their distribution and abundance in most parts of the continent. In this study, we investigated the status of seabird species around the Indian research stations Bharati at Larsemann Hills, Prydz bay and Maitri at Schirmacher Oasis, central Dronning Maud Land located in east Antarctica. We conducted primary surveys during austral summers under the Indian Antarctic Program and compiled published as well as unpublished information on seabird distribution from these areas. We employed intensive area search methods to locate presence of seabird nesting and moulting sites. Ten species were recorded from Larsemann Hills with confirmed breeding of snow petrel, south polar skua and Wilson’s storm-petrel. Only south polar skua and Adélie penguin were reported breeding at Schirmacher Oasis with unconfirmed breeding of Wilson’s storm-petrel. This study presents the first detailed synthesis of status of seabirds from Larsemann Hills and Schirmacher Oasis regions in Antarctica and serves as a strong baseline for future ecological work on seabirds in the sector of operation of Indian Antarctic Program.