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DIET‐TISSUE FRACTIONATION OF STABLE CARBON AND NITROGEN ISOTOPES IN PHOCID SEALS
Author(s) -
Lesage VÉRONIQUE,
Hammill Mike O.,
Kovacs Kit M.
Publication year - 2002
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/j.1748-7692.2002.tb01027.x
Subject(s) - fractionation , trophic level , biology , isotopes of nitrogen , isotope analysis , δ13c , stable isotope ratio , isotope , δ15n , zoology , nitrogen , chemistry , ecology , chromatography , physics , organic chemistry , quantum mechanics
A bstract Diet‐tissue isotopic fractionation of carbon (C) and nitrogen (N) isotopes in short‐ and longer‐term diet integrators of diet ( i. e. , blood serum and red cells), that involve non‐invasive sampling techniques was examined using three species of phocid seals (harbor seals, gray seals, and harp seals) fed a known diet. Variability in diet‐tissue fractionation values within and between species was also scrutinized to determine the legitimacy of using values obtained from one species to explore trophic positions and diets of other related species. All captive seals raised on a constant diet had tissues enriched in 13 C and 15 N relative to their diet. Diet‐tissue isotopic fractionation values were generally consistent among conspecifics and among phocid species for a given tissue. Trophic isotopic enrichment in 13 C was significantly higher in red blood cells (+1.5%±) than in blood serum (+0.8%±), whereas the reverse was observed for nitrogen isotopes (+1.7%± in red cells vs . +3.1%± in serum). However, 13 C‐depleted lipids were not extracted from blood tissues in this study. This results in a downward bias in the diet‐tissue fractionation factors for carbon for both red cells and blood serum, particularly the latter because of their significantly higher lipid contents ( x̄ ± SD = 14.6 ± 2.3%; n = 20; red blood cells 3.8 ± 0.9%±; n = 50, muscle 7.7 ± 2.0; n = 21) in marine mammals.