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TROPHIC RELATIONSHIPS AND THE NITROGEN ISOTOPIC COMPOSITION OF AMINO ACIDS IN PLANKTON
Author(s) -
McClelland J. W.,
Montoya J. P.
Publication year - 2002
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/0012-9658(2002)083[2173:tratni]2.0.co;2
Subject(s) - trophic level , food web , amino acid , plankton , isotopes of nitrogen , phenylalanine , isotope analysis , chemistry , nitrogen , ecosystem , food chain , ecology , environmental chemistry , biology , biochemistry , organic chemistry
Stable nitrogen isotope ratios of whole organisms and tissues are routinely used in studies of trophic relationships and nitrogen flow through ecosystems, yet changes underlying increases in δ 15 N from food source to consumer are not completely understood. In this study, the δ 15 N of 16 amino acids in marine planktonic consumers and their food sources were examined using gas chromatography/combustion/isotope ratio mass spectrometry of their N‐pivaloyl‐i‐propyl‐amino acid ester derivatives. Moderate increases in bulk δ 15 N with trophic position reflect an averaging of large increases in the δ 15 N of some amino acids, and little or no change in others. Amino acids showing consistently large increases (e.g., glutamic acid changes by ∼7‰ between food and consumer) provide greater scope for defining trophic position than the smaller isotopic changes in bulk material. In contrast, amino acids like phenylalanine show no change in δ 15 N with trophic position and therefore preserve information about nitrogen sources at the base of the food web. The ability to acquire information about both trophic level and nitrogen sources at the base of the food web from single samples of consumer tissues offers a powerful new tool for elucidating pathways of N transfer through food webs.