Influence of time-dependent sampling on the plasma metabolome and exposome of fish collected from an effluent-dependent pond

Metabolomics is increasingly recognized as a useful approach to characterize environmental pollution gradients. While the performance of analytical procedures must be validated and documented, many studies only briefly describe sampling and sample storage. Here we advance our recent study on the influences of sampling delay and holding media on contaminants of emerging concern in fish plasma by targeted analysis. We specifically examined the metabolome and exposome of common carp under three conditions: plasma sampled immediately after field collection (t = 0 h) and then after 3 h (t = 3 h) or 20 h (t = 20 h) of holding fish in lab water. Plasma samples were analyzed using reversed-phase and HILIC chromatography with mass spectrometric detection. 6143 of the 12,904 compounds (after clustering features) varied among the groups. We observed different metabolite variation patterns depending on the sample collection time. We also identified several xenobiotics (2-Ethylhexyl sulfate, 6-Chloro-5-methyl-1H-benzotriazole) at concentrations generally found at the highest levels in plasma sampled immediately after field collection (t = 0 h). Both the metabolome and the exposome changed rapidly in fish plasma with a time lag, which indicates that obtaining relevant results is complicated by fish-holding conditions. We further identified that non-lethal, relatively low-volume blood sample collection was sufficient with this species, which presents ethical and practical advantages.