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Discrimination of stable isotopes in fin whale tissues and application to diet assessment in cetaceans
Author(s) -
Borrell A.,
AbadOliva N.,
GómezCampos E.,
Giménez J.,
Aguilar A.
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6267
Subject(s) - krill , whale , baleen , isotope , chemistry , trophic level , stable isotope ratio , δ13c , population , isotope analysis , zoology , biology , fishery , ecology , physics , demography , sociology , quantum mechanics
RATIONALE In stable isotope research, the use of accurate, species‐specific diet‐tissue discrimination factors (i.e., Δ 13 C and Δ 15 N) is central to the estimation of trophic position relative to primary consumers and to the identification of the dietary sources of an individual. Previous research suggested that the diet of fin whales from the waters off northwestern Spain is overwhelmingly based on krill, thus permitting reliable calculation of discrimination values in this wild population. METHODS After confirming that the stable isotope ratios (δ 13 C and δ 15 N values) in muscle from 65 aged fin whales remained constant through age classes (4–65 years), the signatures were determined in muscle, bone protein, skin, liver, kidney, baleen plates and brain, as well as food (krill), from a subset of individuals to calculate discrimination factors. Signatures were determined by means of elemental analysis isotope ratio mass spectrometry (EA‐IRMS) using a ThermoFinnigan Flash 1112. RESULTS The isotopic values remained constant regardless of age. The mean Δ 15 N values between krill and whale tissues ranged from 2.04 in bone protein to 4.27‰ in brain, and those of Δ 13 C ranged from 1.28 in skin to 3.11‰ in bone protein. This variation was consistent with that found in other groups of mammals, and is attributed to variation in tissue composition and physiology. CONCLUSIONS Because discrimination factors are relatively constant between taxonomically close species, the results here obtained may be reliably extrapolated to other cetaceans to improve dietary reconstructions. The skin discrimination factors are of particular relevance to monitoring diet through biopsies or other non‐destructive sampling methods. The large difference in bone protein discrimination factors from those of other tissues should be taken into consideration when bone collagen is used to determine trophic level or to assess diet in paleodietary isotopic reconstructions. Copyright © 2012 John Wiley & Sons, Ltd.