Tissue-specific δC in ancient and modern tropical seabirds and flying fish in the Xisha Islands, South China Sea.

We analyzed C characteristics in samples of bird bones, feathers, eggshell carbonate and membrane from modern specimens of red-footed booby (Sula sula) as well as fish muscle, scales, and bones from its predominant food source, flying fish (Exocoetus volitans), and muscle from its secondary food source squid (Loligo chinensis), as well as in ancient sub-fossil samples of seabird and flying fish at the Xisha Islands, South China Sea. δC is tissue-specific in both seabirds and flying fish due to the variance in turn-over among the tissues and differences in the type and content of amino acids across a diverse range of tissues. The δC discrimination factors also differed significantly among the various tissues between tropical seabirds and their prey. A Suess effect, caused by fossil fuel combustion and the emission of carbon with fewer C isotopes, was observed in the bird and fish tissue from ancient to modern time. Our study provides a multiple variability index for δC in organisms along a food chain, and verifies that tissue-specific C analysis is essential to identify diet and species and thus is a valuable tool for research on tropical seabird ecology.