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The importance of quantifying inherent variability when interpreting stable isotope field data
Carolyn Barnes1, Simon Jennings, Nicholas V C Polunin
1Marine Science and Technology, University of Newcastle upon Tyne, Newcastle, NE1 7RU, UK. carolyn.barnes@hotmail.co.uk
Oecologia
|November 14, 2007
Summary
Inherent variability in stable isotopes (delta(15)N and delta(13)C) significantly impacts diet assessments in fish. Quantifying this individual variation is crucial for accurate ecological and dietary studies.
Area of Science:
- Ecology
- Marine Biology
- Stable Isotope Ecology
Background:
- Stable isotope analysis (delta(15)N and delta(13)C) is widely used to infer diet, trophic position, and niche width.
- Existing studies often overlook or assume inherent individual variability in isotopic signatures, focusing primarily on diet and habitat influences.
Purpose of the Study:
- To quantify the inherent variability of delta(15)N and delta(13)C in European sea bass (Dicentrarchus labrax) under controlled conditions.
- To compare this inherent variability with isotopic variation observed in wild populations.
- To determine the relative contributions of diet versus inherent variability to observed isotopic differences.
Main Methods:
- Rearing European sea bass in a controlled environment with a constant isotopic composition diet.
- Measuring delta(15)N and delta(13)C in individuals from the controlled environment.
- Comparing these measurements with isotopic data from wild European sea bass populations.
Main Results:
- Inherent variability in delta(15)N and delta(13)C among fish on a controlled diet was substantial.
- This inherent variability accounted for a significant portion of the isotopic variation observed in wild populations.
- The contribution of inherent variability was comparable to or even exceeded that of diet variation in some cases.
Conclusions:
- Inherent biological variability is a critical, often underestimated, factor in stable isotope studies of diet.
- Baseline inherent variability must be quantified for specific species, life stages, and environments before interpreting isotopic data from wild populations.
- Accurate dietary assessments using stable isotopes require accounting for individual-level physiological and genetic variations.
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