Application of nitrogen and carbon stable isotopes (δ15Ν and δ13C) to quantify food chain length and trophic structure

Perkins, Matthew J., McDonald, Robbie A., van Veen, F. J. Frank, Kelly, Simon D., Rees, Gareth and Bearhop, Stuart (2014) Application of nitrogen and carbon stable isotopes (δ15Ν and δ13C) to quantify food chain length and trophic structure. PLoS One, 9 (3). ISSN 1932-6203

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Increasingly, stable isotope ratios of nitrogen (delta N-15) and carbon (delta C-13) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using delta N-15, and carbon range (CR) using delta C-13, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in delta N-15 ordelta C-13 from source to consumer) between trophic levels and among food chains. delta N-15 discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. delta C-13 discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of delta C-13 as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of ecological systems.

Item Type: Article
Additional Information: © 2014 Perkins et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Faculty \ School: Faculty of Science > School of Environmental Sciences
Faculty of Science
Depositing User: Pure Connector
Date Deposited: 04 Jul 2014 12:40
Last Modified: 23 Apr 2023 00:38
DOI: 10.1371/journal.pone.0093281


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