Figure 3.

(a) Results of principal component analysis of the variability in metabolite composition of samples incubated for different periods and with different ¹³C₆–glucose concentrations. Metabolites were transformed from ¹³C₆–glucose by a natural aquatic bacterial community, using coastal seawater samples collected on 16 May 2016, 2 June 2016, and 26 April 2017. Numbers in italics beside the symbols indicate the incubation period (days). Non-addition: treatment in which the original seawater was incubated without added ¹³C₆–glucose; glucose-addition: treatment in which the seawater sample was incubated after adding ¹³C₆–glucose (50, 250, or 500 µM C). Loading values for principal components (b) 1 (PC1) and (c) 2 (PC2), showing the top and bottom 15 metabolite signals. Numbers indicate the corresponding metabolites listed in Table 1 (amino acids: red; dipeptides: orange; carboxylic acids: brown; nucleosides and nucleobases: green; carbohydrates: blue; amino alcohols: purple). Greek letters or numbers in parentheses for amino acids and nucleobases, respectively, denote the atom designation. See also Figure S2 for the compounds and chemical classes shown in (b,c). For detailed analytical settings, see Table S1.