Ice matters: Life-history strategies of two Antarctic seals dictate climate change eventualities in the Weddell Sea.

The impacts of climate change in Antarctica and the Southern Ocean are not uniform and ice-obligate species with dissimilar life-history characteristics will likely respond differently to their changing ecosystems. We use a unique data set of Weddell Leptonychotes weddellii and crabeater seals' (CESs) Lobodon carcinophaga breeding season distribution in the Weddell Sea, determined from satellite imagery. We contrast the theoretical climate impacts on both ice-obligate predators who differ in life-history characteristics: CESs are highly specialized Antarctic krill Euphausia superba predators and breed in the seasonal pack ice; Weddell seals (WESs) are generalist predators and breed on comparatively stable fast ice. We used presence-absence data and a suite of remotely sensed environmental variables to build habitat models. Each of the environmental predictors is multiplied by a 'climate change score' based on known responses to climate change to create a 'change importance product'. Results show CESs are more sensitive to climate change than WESs. Crabeater seals prefer to breed close to krill, and the compounding effects of changing sea ice concentrations and sea surface temperatures, the proximity to krill and abundance of stable breeding ice, can influence their post-breeding foraging success and ultimately their future breeding success. But in contrast to the Ross Sea, here WESs prefer to breed closer to larger colonies of emperor penguins (Aptenodytes forsteri). This suggests that the Weddell Sea may currently be prey-abundant, allowing the only two air-breathing Antarctic silverfish predators (Pleuragramma antarctica) (WESs and emperor penguins) to breed closer to each other. This is the first basin-scale, region-specific comparison of breeding season habitat in these two key Antarctic predators based on real-world data to compare climate change responses. This work shows that broad-brush, basin-scale approaches to understanding species-specific responses to climate change are not always appropriate, and regional models are needed-especially when designing marine protected areas.