Defining the Baseline and Oxidant Perturbed Lipidomic Profiles of Daphnia magna.

Recent technological advancement has enabled the emergence of lipidomics as an important tool for assessing molecular stress, one which has yet to be assessed fully as an approach in an environmental toxicological context. Here we have applied a high-resolution, non-targeted, nanoelectrospray ionisation (nESI) direct infusion mass spectrometry (DIMS) technique to assess the effects of oxidative stress to both in vitro (air exposure of daphniid extracts) and in vivo (Cu exposure). Multivariate and univariate statistical analyses were used to distinguish any perturbations including oxidation to the baseline lipidome. This approach enabled the putative annotation of the baseline lipidome of with 65% of the lipid species discovered previously not reported. In vitro exposure of lipid extracts to air, primarily to test the methodology, revealed a significant perturbation to this baseline lipidome with detectable oxidation of peaks, in most cases attributed to single oxygen addition. Exposure of to Cu in vivo also caused a significant perturbation to the lipidome at an environmentally relevant concentration of 20 µg/L. This nESI DIMS approach has successfully identified perturbations and oxidative modifications to the lipidome in a high-throughput manner, highlighting its suitability for environmental lipidomic studies.