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

Abstract

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.