Collection of delta-15 N values of specific amino acids in oceanic samples

Nitrogen stable isotope analysis in specific amino acids (δ15N AA-CSIA) is a technique widely used to estimate the trophic position of an organism. The difference between the δ15N of a “trophic” amino acid, typically glutamic acid/glutamine (Glx), and a “source” amino acid, typically phenylalanine (Phe), is a trophic index that, combined with the isotopic discrimination caused by the primary producers (β) and by the trophic steps (TDF), is used to estimate the trophic position. The TDF between Glu and Phe, however, is not as universal as originally thought, and the calculated TPs were underestimated in high trophic level species. This database metanalysis combine data from 92 studies and has been used to investigate other possible amino acid combinations to estimate the trophic position.