The importance of quantifying inherent variability when interpreting stable isotope field data |
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Authors: | Carolyn Barnes Simon Jennings Nicholas V C Polunin John E Lancaster |
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Institution: | (1) Marine Science and Technology, University of Newcastle upon Tyne, Newcastle, NE1 7RU, UK;(2) Ecosystem Interactions, Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, Suffolk, NR33 0HT, UK;(3) School of the Environment and Society, University of Wales, Singleton Park, Swansea, SA2 8PP, UK |
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Abstract: | Stable isotope data are often used to assess diet, trophic level, trophic niche width and the extent of omnivory. Notwithstanding
ongoing discussions about the value of these approaches, variations in isotopic signatures among individuals depend on inherent
variability as well as differences in feeding habitats. Remarkably, the relative contributions of diet variation and inherent
variability to differences in δ15N and δ13C among individuals have not been quantified for the same species at the same life history stages, and inherent variability
has been ignored or assumed. We quantified inherent variability in δ13C and δ15N among individuals of a marine fish (the European sea bass, Dicentrarchus labrax) reared in a controlled environment on a diet of constant isotopic composition and compared it with variability in δ13C and δ15N among individuals from wild bass populations. The analysis showed that inherent variability among reared individuals on
a controlled diet was equivalent to a large proportion of the observed variability among wild individuals and, therefore,
that inherent variability should be measured to establish baseline variability in wild populations before any assumptions
are made about the influence of diet. Given that inherent variability is known to be dependent on species, life history stage
and the environment, our results show that it should be quantified on a case-by-case basis if diet studies are intended to
provide absolute assessments of dietary habits. |
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Keywords: | Carbon Feeding Food chain Food web Nitrogen Stable isotopes |
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