Responses of seabirds, in particular prions (Pachyptila sp.), to small-scale processes in the Antarctic Polar Front

Van Franeker, J.A., Van Den Brink, N.W., Bathmann, U.V., Pollard, R.T., De Baar, H.J.W. and Wolff, W.J. (2002) Responses of seabirds, in particular prions (Pachyptila sp.), to small-scale processes in the Antarctic Polar Front. Deep Sea Research Part II: Topical Studies in Oceanography, 49 (18), 3931-3950. (doi:10.1016/S0967-0645(02)00118-2).

Abstract

Small-scale distribution patterns of seabirds in the Antarctic Polar Front (APF) were investigated in relation to other biological, physical, and chemical features during the ANT-XIII/2 research cruise of R.V. Polarstern from December 1995 to January 1996. The APF is characterized by steep gradients in sea-surface temperature and salinity. Within the APF, gradient zones were closely associated with elevated levels of primary production, chlorophyll-a (chl-a) concentrations, and zooplankton densities. Even broad-billed prions (‘Pachyptila vittata-group’), which dominated the seabird community by 83% in carbon requirements, showed small-scale distributional patterns that were positively related to primary production, chl-a, and total zooplankton densities. The findings demonstrate a close, direct link between fine-scale physical processes in the APF and biological activity through several food web levels up to that of zooplankton-eating seabirds. Broad-billed prions appeared to forage on very small copepods (Oithona spp.) in close association with the front. Fish- and squid-eating predators showed poor correlations with small-scale spatial structures of the APF. However, in a wider band around the APF, most top predators did occur in elevated densities, showing gradual spatio-temporal diffusion of the impact of the APF on higher trophic levels.

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