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Title: Advances in the application of amino acid nitrogen isotopic analysis in ecological and biogeochemical studies

Author
item OHKOUCHI, NACHIKO - Japan Agency For Marine-Earth Science And Technology (JAMSTEC)
item CHIKARAISHI, YOSHITO - Japan Agency For Marine-Earth Science And Technology (JAMSTEC)
item CLOSE, HILARY - University Of Miami
item FRY, BRIAN - Griffiths University
item LARSEN, THOMAS - University Of Kiel
item MADIGAN, DANIEL - Harvard University
item MCCARTHY, MATTHEW - University Of California
item MCMAHON, KELTON - University Of California
item NAGATA, TOSHI - Research Institute For Humanity And Nature (RIHN)
item NAITO, YUICHI - Japan Agency For Marine-Earth Science And Technology (JAMSTEC)
item Steffan, Shawn

Submitted to: Organic Geochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2017
Publication Date: 8/1/2017
Publication URL: http://handle.nal.usda.gov/10113/5810276
Citation: Ohkouchi, N., Chikaraishi, Y., Close, H.G., Fry, B., Larsen, T., Madigan, D.J., McCarthy, M.D., McMahon, K.W., Nagata, T., Naito, Y.I., Steffan, S. et al. 2017. Advances in the application of amino acid nitrogen isotopic analysis in ecological and biogeochemical studies. Organic Geochemistry. 113:150-174. https://doi.org/10.1016/j.orggeochem.2017.07.009.

Interpretive Summary: This paper reviews the latest technological advances and ecological discoveries deriving from compound-specific analyses of nitrogen isotopes in amino acids. Impact: Given that isotopes encode information on the flow of matter and energy through all living and non-living things, the analysis of isotopic signatures has long represented a very cross-cutting, powerful tool in the biological and geochemical sciences. This review paper reports on major advances in isotopic analysis (particularly, amino acid-specific analysis of nitrogen isotopes). The paper will consolidate the latest information on this approach, and will establish tools and paradigms for much future scientific research.

Technical Abstract: Compound-specific isotopic analysis of amino acids (CSIA-AA) has emerged in the last decade as a powerful approach for tracing the origins and fate of nitrogen in ecological and biogeochemical studies. This approach is based on the empirical knowledge that source AAs (i.e., phenylalanine), fractionate 15N very little (<0.5‰) during trophic transfer, whereas trophic AAs (i.e., glutamic acid), are greatly (~6-8‰) enriched in 15N during each trophic step. The differential fractionation of these two AA groups can provide a valuable estimate of consumer trophic position that is internally indexed to the baseline d15N value of the integrated food web. In this paper, we critically review the analytical methods for determining the nitrogen isotopic composition of AAs by gas chromatography/isotope-ratio mass spectrometry. We also discuss methodological considerations for accurate trophic position assessment of organisms using CSIA-AA. We then discuss the advantages and challenges of the CSIA-AA approach by examining published studies including trophic position assessment in various ecosystems, reconstruction of ancient human diets, reconstruction of animal migration and environmental variability, and assessment of marine organic matter dynamics. It is clear that the CSIA-AA approach can provide unique insight into the sources, cycling, and trophic modification of organic nitrogen as it flows through systems. However, some uncertainty still exists in how biochemical, physiological, and ecological mechanisms affect isotopic fractionation of trophic AAs. We end this review with a call for continued exploration of the mechanisms of AA isotopic fractionation, through various studies to promote the evolution of the rapidly growing field of CSIA-AA.