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Application of Nitrogen and Carbon Stable Isotopes (δ15N and δ13C) to Quantify Food Chain Length and Trophic Structure

Matthew Perkins, Robbie A. McDonald, F. J. Frank van Veen, Simon D. Kelly, Gareth Rees, Stuart Bearhop

PLoS ONE, Volume: 9, Issue: 3, Start page: e93281

Swansea University Author: Matthew Perkins

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Abstract

Increasingly, stable isotope ratios of nitrogen (d15N) and carbon (d13C) are used to quantify trophic structure, thoughrelatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plantinvertebratefood chains spanning four trophic levels we es...

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Published in: PLoS ONE
ISSN: 1932-6203
Published: 2014
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa44817
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Abstract: Increasingly, stable isotope ratios of nitrogen (d15N) and carbon (d13C) are used to quantify trophic structure, thoughrelatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plantinvertebratefood chains spanning four trophic levels we estimated nitrogen range (NR) using d15N, and carbon range (CR)using d13C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range ofknown food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimatesof structure are robust because they were calculated using resampling procedures that propagate variance in sample meansthrough to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, weadditionally examined variation in discrimination (which is change in d15N or d13C from source to consumer) betweentrophic levels and among food chains. d15N discrimination showed significant enrichment, while variation in enrichmentwas species and system specific, ranged broadly (1.4% to 3.3%), and importantly, propagated variation to subsequentestimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though someoverlap between longer food chains infers a need for awareness of such limitations. d13C discrimination was inconsistent;generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little withincreasing food chain length, showing the potential utility of d13C as a tracer of energy pathways. This study serves as arobust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximatefour trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chainsmakes our findings relevant for a majority of ecological systems.
College: Faculty of Science and Engineering
Issue: 3
Start Page: e93281