Seasonal variation in the stomach microbiota of two sympatrically breeding Pygoscelis penguin species at Signy Island, South Orkney Islands

Abstract

The gut microbiomes of Antarctic penguins are important for the fitness of the host birds and their chicks. The compositions of microbial communities in Antarctic penguin guts are strongly associated with the birds' diet, physiological adaptation and phylogeny. Whilst seasonal changes in food resources, distribution and population parameters of Antarctic penguins have been well addressed, little research is available on the stability or variability of penguin stomach microbiomes over time. Here, we focused on two Pygoscelis penguin species breeding sympatrically in the maritime Antarctic and analysed their stomach contents to assess whether penguin gut microbiota differed over three austral summer breeding seasons. We used a high-throughput DNA sequencing approach to study bacterial diversity in stomach regurgitates of Adélie (Pygoscelis adeliae) and chinstrap (Pygoscelis antarctica) penguins that have a similar foraging regime on Signy Island (South Orkney Islands). Our data revealed significant differences in bacterial alpha and beta diversity between the study seasons. We also identified bacterial genera that were significantly associated with specific breeding seasons, diet compositions, chick-rearing stages and sampling events. This study provides a baseline for establishing future monitoring of penguin gut microbiomes in a rapidly changing environment.

Keywords: Antarctic krill; diet; microbiome; penguins; sea ice; seasonal variation.

Fig. 1.. Relative abundances of the frequently encountered bacterial (a) phyla and (b) genera in the stomach regurgitates of Adélie and chinstrap penguins collected at each sampling event across the three penguin breeding seasons.

Fig. 2.. Comparison of alpha diversity values between (a) Adélie and chinstrap penguins, (b) different breeding seasons of Adélie penguins and (c) different diet compositions of Adélie penguins.

Fig. 3.. Comparison of beta diversity values between (a) Adélie and chinstrap penguins, (b) different sampling events of both penguin species, (c) different breeding seasons of Adélie penguins and (d) different chick-rearing stages of chinstrap penguins in the breeding season 2011/2012.

Fig. 4.. LEfSe shows bacterial genera that were significantly associated with the different (a) sampling events, (b) breeding seasons, (c) chick-rearing stages and (d) diet compositions. The genera are ranked in increasing order of LDA scores as shown on the X-axis, whilst the heatmap at the right of the plot indicates whether the abundance of a genus was higher (towards red) or lower (towards blue).