MEPS 391:293-306 (2009)  -  DOI: https://doi.org/10.3354/meps08215

ABSTRACT: We determined the δ¹⁵N and δ¹³C values of individual amino acids (AAs) isolated from chick blood of 4 penguin species that forage in different oceanic regions (from the subtropics of the Indian Ocean to Antarctica) to test if: (1) the δ¹⁵N values of phenylalanine (δ¹⁵N _phe) revealed different foraging areas among the species; (2) the difference between glutamic acid and phenylalanine δ¹⁵N values (Δδ¹⁵N_glu-phe) accurately predicted trophic levels; and (3) the δ¹³C value of AAs could resolve species foraging locations, similar to bulk δ¹³C values. The δ¹³C values of all AAs decreased with latitude, were positively correlated with bulk δ¹³C data, and, therefore, tracked the isotopic baseline. However, we were not able to discern additional ecological information from these δ¹³C values. In contrast, the δ¹⁵N values of AAs distinguished the isotopic value of the nitrogen at the base of the food web from the trophic level of the consumer, providing new insight for the study of the trophic ecology of seabirds. The difference in the bulk δ¹⁵N values of northern and southern rockhopper penguins Eudyptes chrysocome ssp. was due to both a difference in their foraging location (different δ¹⁵N _phe) and their trophic levels (different Δδ¹⁵N_glu-phe). The δ¹⁵N _phe values of king Aptenodytes patagonicus and Adélie penguins Pygoscelis adeliae were higher than those of rockhoppers, which could reflect a foraging on mesopelagic prey for king penguins and, in the highly productive Antarctic shelf waters, for Adelie penguins. The Δδ¹⁵N_glu-phe accurately reflected the relative trophic level of penguins, but further work is required to determine the trophic enrichment factors for compound-specific isotope analysis.

KEY WORDS: δ¹⁵N · δ¹³C · Compound specific · Isotopic niche · Trophic level

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Cite this article as: Lorrain A, Graham B, Ménard F, Popp B, Bouillon S, van Breugel P, Cherel Y (2009) Nitrogen and carbon isotope values of individual amino acids: a tool to study foraging ecology of penguins in the Southern Ocean. Mar Ecol Prog Ser 391:293-306. https://doi.org/10.3354/meps08215 Export citation Share:    Facebook - - linkedIn