MEPS 434:1-13 (2011)  -  DOI:

Trophic versus geographic structure in stable isotope signatures of pelagic seabirds breeding in the northeast Atlantic

Jose Luis Roscales1,2,*, Elena Gómez-Díaz1,3, Verónica Neves4, Jacob González-Solís1

1Institut de Recerca de la Biodiversitat and Dept. Biologia Animal, Universitat de Barcelona, Av. Diagonal 645,
08028 Barcelona, Spain
2Dept. of Instrumental Analysis and Environmental Chemistry, Institute of Organic Chemistry, Spanish National Research Council (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain
3Institute of Evolutionary Biology (CSIC-UPF), Passeig Maritim de la Barceloneta 37-49, 08003 Barcelona, Spain
4Instituto do Mar, Cais de Santa Cruz, 9901-862 Horta, Açores, Portugal

ABSTRACT: Feeding ecology and geographic location are 2 major factors influencing animal stable isotope signatures, but their relative contributions are poorly understood, which limits the usefulness of stable isotope analysis in the study of animal ecology. To improve our knowledge of the main sources of isotopic variability at sea, we determined δ15N and δ13C signatures in the first primary feather of adult birds from 11 Procellariiform species (n = 609) across 16 northeast Atlantic localities, from Cape Verde (20°N) to Iceland (60°N). Post-breeding areas (where the studied feather is thought to be grown) were determined using light-level geolocation for 6 of the 11 species. Isotopic variability was geographically unstructured within the mid-northeast Atlantic (Macaronesian archipelagos), but trophically structured according to species and regardless of the breeding location, presumably as a result of trophic segregation among species. Indeed, the interspecific isotopic overlap resulting from combining δ15N and δ13C signatures of seabirds was low, which suggests that most species exploited exclusive trophic resources consistently across their geographic range. Species breeding in north temperate regions (Iceland, Scotland and Northern Ireland) showed enriched δ15N compared to the same or similar species breeding in tropical and subtropical regions, suggesting some differences in baseline levels between these regions. The present study illustrates a noticeable trophic segregation of northeast Atlantic Procellariiformes. Our results show that the isotopic approach has limited applicability for the study of animal movements in the northeast Atlantic at a regional scale, but is potentially useful for the study of long-distance migrations between large marine systems.

KEY WORDS: Feeding ecology · Marine isoscapes · Migratory movements · Procellariiformes · Trophic niche

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Cite this article as: Roscales JL, Gómez-Díaz E, Neves V, González-Solís J (2011) Trophic versus geographic structure in stable isotope signatures of pelagic seabirds breeding in the northeast Atlantic. Mar Ecol Prog Ser 434:1-13.

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