At-Sea Distribution of Seabirds and Marine Mammals in the Unexplored Southern Weddell Sea, Antarctica

Background: In the frame of our long-term study in polar seas, the at-sea distribution of “top predators” – seabirds and marine mammals – was studied in the Weddell Sea area, both the well-covered northern one (sub-antarctic Scotia Sea) as well as in the almost unexplored southern and central ones. Method was our usual transect counts lasting 30 min. each, without width limitation. Results and conclusions: Species richness was low, dominated by only a few species, reflecting low diversity. Birds, seals and to some extend whales showed a heterogeneous distribution. They were concentrated in a few “hotspots” on the “continental” shelf and –slope, of South Georgia, South Sandwich and South Shetland (Elephant) islands, and off the Peninsula. Species showed important differences in distribution probably reflecting differences in the food web. In open waters off the shelf, species showed low densities, both in the northern and southern areas. In the case of seabirds, moreover, they were partially over-estimated by the presence of long-distance followers, probably by one order of magnitude. The absence of gentoo penguin might reflect a change in geographical distribution.