MEPS 391:293-306 (2009)  -  DOI:

Nitrogen and carbon isotope values of individual amino acids: a tool to study foraging ecology of penguins in the Southern Ocean

Anne Lorrain1,*, Brittany Graham2,3, Frédéric Ménard4, Brian Popp5, Steven Bouillon6,7,8, Peter van Breugel6, Yves Cherel9

1IRD/LEMAR, Centre IRD de Brest, BP 70, 29280 Plouzané, France
2Department of Oceanography, University of Hawaii, Honolulu, Hawaii 96822, USA
3SINLAB, Canadian Rivers Institute, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada
4IRD, UMR 212 EME, Centre de Recherche Halieutique (CRH), Avenue Jean Monnet, BP 171, 34203 Sète Cedex, France
5Department of Geology and Geophysics, University of Hawaii, 1680 East-West Rd., Honolulu, Hawaii 96822, USA
6Centre for Estuarine and Marine Ecology, Netherlands Institute of Ecology (NIOO-KNAW), PO Box 140, 4400 AC Yerseke, The Netherlands
7Dept. of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
8Dept. of Earth & Environmental Sciences, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium
9CEBC, UPR 1934 du CNRS, BP 14, 79360 Villiers-en-Bois, France

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 (Δδ15Nglu-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 Δδ15Nglu-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 Δδ15Nglu-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.

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