Trophic versus geographic structure in stable isotope signatures of pelagic seabirds breeding in the northeast Atlantic
Baseline geographic variability and feeding ecology are two major factors shaping stable isotope signatures in marine animals, but their relative contributions are unclear. Roscales and colleagues examined δ15N and δ13C in feathers of pelagic seabirds throughout the NE Atlantic and tracked seabird movements with geolocators. Isotopic signatures from multiple localities mostly aggregated according to the species, suggesting trophic niche is the prime source of isotopic variability. Signatures were geographically unstructured within large marine regions and only differed at large spatial scales, i.e. north temperate versus tropical and subtropical regions. Therefore, stable isotopes are effective dietary tracers of marine animals at a regional scale, and can be used as intrinsic markers to trace migratory movements among distant marine regions.
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