Abstract
The Ross Sea, Antarctica, supports large populations of Emperor Penguin (Aptenodytes forsteri) and Adélie Penguin (Pygoscelis adeliae), two key meso-predators that occupy high trophic levels. Despite these species are largely studied, little is known about their diet outside the breeding period. In the present study, we investigated the intra-annual diet of Adélie and Emperor Penguins belonging to five colonies in the Ross Sea through the stable isotope analysis of different tissues (feathers and shell membranes), synthetized in different seasons, and guano that indicates recent diet. Penguin samples and prey (krill and fish) were collected during the Antarctic spring–summer. δ13C and δ15N of tissues and guano indicate spatio-temporal variation in the penguin diet. The krill consumption by Adélie Penguins was lowest in winter except in the northernmost colony, where it was always very high. It peaked in spring and remained prevalent in summer. The greatest krill contribution to Emperor Penguin’s diet occurred in summer. The relative krill and fish consumption by both species changed in relation to the prey availability, which is influenced by seasonal sea ice dynamics, and according to the penguin life cycle phases. The results highlight a strong trophic plasticity in the Adélie Penguin, whose dietary variability has been already recognized, and in the Emperor Penguin, which had not previously reported. Our findings can help understand how these species might react to resource variation due to climate change or anthropogenic overexploitation. Furthermore, data provides useful basis for future comparisons in the Ross Sea MPA and for planning conservation actions.
Highlights
The Ross Sea is one of the most biologically productive regions of the Antarctic continent (Arrigo et al 2002)
These penguin species are extensively studied due to their considerable ecological and conservation importance, studies related to their trophic ecology are limited to specific periods of the year, such as the chick-rearing period that corresponds to summer for Adélie Penguin and spring for Emperor Penguin (Tierney et al 2008; Juáres et al 2016)
For the Adélie Penguin there is a paucity of diet information in spring, and for the Emperor Penguin little is known about its trophic ecology in summer (Cherel 2008)
Summary
The Ross Sea is one of the most biologically productive regions of the Antarctic continent (Arrigo et al 2002) It is characterized by high biodiversity (Laffoley et al 2019) and since October 2016 it is the largest marine protected area in the world (Brooks et al, 2020). It has a diet based mainly on fish and, to a lesser extent, on crustaceans These penguin species are extensively studied due to their considerable ecological and conservation importance, studies related to their trophic ecology are limited to specific periods of the year, such as the chick-rearing period that corresponds to summer for Adélie Penguin and spring for Emperor Penguin (Tierney et al 2008; Juáres et al 2016). Very few data are available on the winter diet of both species (Wienecke and Robertson 1997; Burns and Kooyman 2001)
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