Traditionally, bioassays are used to assess the toxicity of chemicals. Bioassays often focus on
one specific mode of action or end point and their responses offer a limited understanding of the health status and underlying
pathways of the species under consideration. Metabolomics can be used to detect hundreds of metabolites in which
each metabolite, or set of metabolites, represents short term and long term changes, indicating the status of the organism.
The effects of the herbicide diuron, one of the compounds of concern for European water bodies, on the marine microalgae
Dunaliella tertiolecta were investigated through non-target metabolomic profiling and bioassay testing. The pulse
amplitude modulation (PAM) fluorometry bioassay was employed to measure the effective photosystem II efficiency
(ϕPSII), while non-target metabolomic profiling using complementary analytical techniques characterized the metabolomic
response in the algae during diuron exposure. The use of complementary analytical techniques was necessary to
identify a broad range of metabolites. Twenty-eight compounds were identified as metabolites affected by diuron exposure,
including several amino acids, adenosine, lactic acid, and citric acid. Collectively, these metabolites indicated that
diuron negatively affects energy processes in the algae both at the citric acid cycle pathway as well as on the amino acid metabolism
at realistic environmental concentrations. In addition, dose-response relationships were found between a number of
affected metabolites and the inhibition of the ΦPSII of D. tertiolecta. Non-target metabolomic profiling using complementary
analytical techniques proved to have additional and complementary benefits to traditional toxicology tests.