Spatio-temporal persistence of top predator hotspots near the Antarctic Peninsula

We quantified species richness and abundance of seabirds and marine mammals in order to identify marine areas that are persistently attractive to top predators. Shipboard surveys across a 150 000 km(2) grid off the Antarctic Peninsula were conducted once or twice each year from 2003 to 2011 during which the distribution and abundance of top predators were mapped. We hypothesized that spatial organization of species richness and abundance hotspots reflect persistent habitat use and are regionalized according to distance from land and oceanographic boundaries. To test this, we used a new hotspot variance metric based on the percentage of time that the species richness or abundance estimate at any one location is greater than 1 standard deviation above the long term means for the entire survey grid. Species richness hotspots were based on all species sighted, while abundance hotspots were based on concentrations of 16 species: 13 seabirds (penguins, petrels and albatrosses), 1 pinniped and 2 baleen whales. Species abundance hotspots reflected 2 major groupings-those with oceanic and coastal origins. We identified 15 richness hotspots, 9 of which were in proximity to the southern Antarctic Circumpolar Current front; the 6 others were associated with major breeding colonies and the location of 2 submarine canyon systems. Our approach integrates temporal and spatial variances over 14 individual surveys and provides useful reference points for identifying ecologically important areas, refining food web models and developing spatial management of and conservation strategies for marine ecosystems.