Polystyrene nanoplastics modify phenanthrene-associated metabolic responses in the marine clam Mactra veneriformis

Phenanthrene (Phe) and plastic particles can co-occur in coastal waters, but their combined metabolic effects in marine bivalves remain uncertain. We exposed Mactra veneriformis to nominal Phe concentrations of 20, 50, or 100 μg L^-1, 1 mg L^-1 polystyrene nanoplastics (PS-NPs), or their combinations for 8 d. Non-targeted LC-MS data were reanalyzed using the aquarium as the independent experimental unit, yielding three aquarium-level profiles per treatment. Of 543 MS/MS-annotated metabolites, 36, 118, 164, and 139 met prespecified effect-size and Welch-FDR criteria in the PS-NP versus control and the three solvent-matched Phe-plus-PS-NP versus Phe comparisons, respectively. Sixteen metabolites met these criteria in all four comparisons. Exact permutation tests of the supervised models gave P = 0.10, and no KEGG pathway remained significant after FDR correction. Dynamic light scattering showed that nominal 80 nm PS-NPs formed polydisperse aggregates in artificial seawater, reaching 1664 ± 511 nm after 24 h in the highest-Phe medium. These results show that PS-NPs were associated with changes in Phe-related metabolomic response patterns under the tested suspension conditions, but they do not identify a carrier-mediated mechanism or establish environmentally representative effects.