Fig. 5
Possible classification of amino acids: a source-essential, b trophic-essential, and c trophic-nonessential on the cross-plot of the Δδ15N and Δδ13C values
Fig. 5 | Progress in Earth and Planetary Science
Possible classification of amino acids: a source-essential, b trophic-essential, and c trophic-nonessential on the cross-plot of the Δδ15N and Δδ13C values