COS 158-6 - Krill hotspot persistence drives Pygoscelis penguin biogeography & diet composition

Abstract: Pygoscelis penguins are central place foragers during the austral summer, meaning that they must return to their nests to provision their growing chicks. Optimal foraging theory suggests that this behavior is only feasible if resources are abundant adjacent to the penguin colonies. However, prey availability to penguins, especially of the Antarctic krill, a keystone species along the West Antarctic Peninsula (WAP), is difficult to quantify. Recent modeling studies near Palmer Deep Canyon have illustrated that local penguin colonies are adjacent to areas of high simulated krill accumulation. This suggests that the accumulation of prey may be an important driver of Pygoscelis penguin biogeography.



Here, we test the hypothesis that Pygoscelis penguins are preferentially located near areas of high prey accumulation across the entire WAP. Using simulated krill within the Regional Ocean Modeling System (ROMS), we calculate the persistence of krill hotspots throughout the coastal ocean along the WAP across eight austral summers. We then compare the distribution of hotspot persistence within the foraging ranges of known Pygoscelis penguin colonies and randomly selected colony locations. Preliminary results suggest that selection is present across four of the eight austral summers simulated to date, supporting our hypothesis that penguin biogeography along the WAP is driven, in part, by prey availability.



To determine if penguins located near persistent krill hotspots are consuming more krill, we use satellite-based estimates of Pygoscelis diets. We hypothesize that colonies that are closer to more persistent hotspots will have a larger fraction of krill in their diets due to higher prey availability. Results supporting this hypothesis would suggest not only that the model is, to a degree, accurately predicting krill accumulation, but that prey accumulation impacts diet composition in Pygoscelis penguins. Together, these results will provide powerful insights into the factors driving penguin biogeography along the WAP. These results will allow us to build habitat suitability models based on modeled prey fields, which may be used to predict range expansion or contraction of Pygoscelis penguins.