Highlights
- OA reduces TiO₂ NPs aggregation/sedimentation, increasing NP bioaccumulation
- NPs preferentially accumulate in liver, inducing hepatotoxicity via oxidative stress
- Size effect outweighs biological resistance as primary NP toxicity driver under OA
- Combined OA-NPs suppress hepatic genes, activate senescence and cell death pathways
- First evidence quantifying hydrodynamic size dominance in OA-enhanced NP toxicity
ABSTRACT
Ocean acidification (OA) and engineered nanoparticles (NPs) pollution represent two critical global environmental challenges. Marine organisms are suffering from their combined stress. However, few studies address their combined effects, and the toxicity mechanisms of NPs under OA are largely unresolved. In this study, we investigated the responses of the marine medaka Oryzias melastigma to environmentally relevant concentration of TiO2 NPs (1.0 mg/L) under OA (pH 7.40). We found that OA alleviated the aggregation and sedimentation of NPs, and decreased the resistance ability of the marine medaka to NPs stress, leading to elevated bioaccumulation of TiO2 NPs. Notably, NPs preferentially accumulated in the liver, inducing hepatotoxicity through oxidative stress and histopathological and ultrastructural damage. Critically, an integrated biomarker approach quantified the relative contributions of size effects (58%) and biological resistance (42%) to NP toxicity under OA, demonstrating that hydrodynamic size dominates toxicity outcomes. Transcriptomic analysis further revealed suppressed hepatic gene transcription and translation, alongside activated cellular senescence and programmed cell death pathways under combined exposure. These findings provide critical insight into the combined toxicity mechanisms of NPs and OA, significantly advancing our understanding of the profound risks that NPs pose to marine ecosystems under OA conditions.
Zhu L., Zou L., Nie M., Xia B., Zhao J., Sui Q., Sun X. & Xing B., 2025. Ocean acidification enhances TiO2 nanoparticle toxicity in Oryzias melastigma: dominant role of size effects in driving bioaccumulation and hepatotoxicity. Water Research 289 (Part A): 124822. doi: 10.1016/j.watres.2025.124822. Article (restricted access).
