Molecular diet analysis of Pygoscelis adeliae in the Ross Sea using fecal DNAs

As the most abundant penguin species, the diet of Adélie penguin, Pygoscelis adeliae, would be one of the most important indicators for the ecosystem conditions where they inhabit. The diet of seven Adélie penguin populations in the Ross Sea was studied using both metabarcoding and quantitative PCR (qPCR) analyses. 18Sv9 and miniFish primers provided the overall diet compositions and accurate fish species names, respectively. Based on the metabarcoding analysis, main prey items for Adélie penguin were notothenioid fish, Euphausia superba, and Euphausia crystallorophias varies from small fishes. Among the notothenioid fish, three species, including Pleuragramma antarctica, Pagothenia borchgrevinki, and Trematomus spp. were most abundant. qPCR analysis showed a significant geographical difference in the ratio between krill and notothenioids. Populations inhabiting inbound parts of Ross Sea (Edmonson Point and Inexpressible island) showed higher proportions of fish taxa without E. superba, while the other five populations exhibited a higher krill ratio to fish taxa with two krill. The ratio of krill to fish taxa was highly variable for three-year of study and showed annual synchronous patterns in observed populations, suggesting the long-term study for the penguin’s diet should be conducted to understand the relationship between the populations of Adélie penguin and their marine ecosystem in the Ross Sea.