Comparative toxicities of leachates from aquaculture plastics and automobile tires in Dunaliella primolecta and Tigriopus japonicus

Abstract The chemical impacts of synthetic polymer leachates on marine ecosystems are a growing concern. This study evaluated the acute ecotoxicity of leachates from three prevalent materials in Hiroshima Bay: polyethylene (PE) pipes used as aquaculture spacers, expanded polystyrene (EPS) used as floats, and automobile tires from road runoff and ship fenders. We exposed the marine microalga Dunaliella primolecta and the copepod Tigriopus japonicus to these leachates and characterized their chemical profiles using non-target gas chromatography–mass spectrometry screening. The results showed that PE and EPS leachates exerted negligible acute toxicity on both species at the maximum tested concentration (5.4 g/L), suggesting a low ecological risk under currently projected levels. Conversely, tire leachate exhibited significant toxicity, with median effective concentration (EC 50 ) values of 2.7 g/L for D. primolecta and 0.67 g/L for T. japonicus . This fourfold higher sensitivity in the copepod suggests a potential threat to crustacean recruitment. Chemical analysis identified tire-specific constituents, such as aniline, 1,3-benzothiazole, dicyclohexylamine, and N-phenyl- p -benzoquinone imine. These compounds may contribute to toxicity by inducing physiological stress in both primary producers and consumers. Our findings demonstrate that while the tested aquaculture plastics pose lower immediate chemical risks, unweathered tire-derived chemicals represent a significant latent threat to fishery resources in productive coastal ecosystems.