The distribution of seabirds and pinnipeds in Marguerite Bay and their relationship to physical features during austral winter

The distribution of seabirds and pinnipeds in Marguerite Bay and their relationship to physical features during austral winter 2001

Erik W. Chapman, Christine A. Ribic, and William R. Fraser

The distribution of seabirds and pinnipeds and their relationship to physical oceanographic variables were investigated within the U.S. Southern Ocean Global Ocean Ecosystems Dynamics (U.S. SO GLOBEC) program for late fall (April-May) and winter (July-August) cruises conducted during 2001. Top predators were surveyed and physical oceanographic variables measured along a study grid near Marguerite Bay on the West Antarctic Peninsula. Sea ice conditions during the cruise provided a unique opportunity to compare the relationship among physical oceanographic variables and species distributions before and after the development of pack ice. Before pack ice development, ice-affiliated species (southern fulmar (Fulmarus glacialoides), Antarctic petrel (Thalassoica antarctica) and snow petrel (Pagodroma nivea)) and open water-affiliated species (cape petrel (Daption capense) and blue petrel (Halobaena caerulea)) were observed in the area. In addition, Antarctic fur seal (Arctocephalus gazella) and crabeater seal (Lobodon carcinophagus) were observed in low numbers. Seabirds were associated with the water column environment, in particular, water mass structure. The birds had higher densities in Inner Shelf Water, particularly near Alexander Island where a strong, coastal current had developed. After the development of pack ice, only ice-affiliated species (snow petrel, Antarctic petrel, Adélie penguin (Pygoscelis adeliae), and crabeater seal) were observed. Seabirds were primarily associated with ice characteristics (e.g., ice concentration, ice type) rather than the water column environment. The timing and extent of sea ice development in the fall may have important effects on over-winter predation by seabirds and pinnipeds on zooplankton and fish on the Western Antarctic Peninsula.

STATUS UPDATE

FINAL VERSION READY (hard copy + electronic version)