Influences of different functional groups on the toxicity of pyrene derivatives to Skeletonema costatum: Interactive...

Polycyclic aromatic hydrocarbons (PAHs) and microplastics, as persistent contaminants in the marine environment, have attracted significant attention for their potential risks. However, the toxicology of substituted PAHs (S-PAHs) in marine microalgae and the modulation of their toxicity by microplastics remain underexplored. Here, the toxicity of pyrene (Pyr) and derivatives of pyrene (S-Pyr), including 1-methylpyrene (P-CH₃), 1-hydroxypyrene (P-OH), 1-aminopyrene (P-NH₂), 1-pyrenecarboxylic acid (P-COOH) on the marine diatom Skeletonema costatum, both in the absence and presence of polystyrene microplastics (micro-PS) was investigated. Compared to Pyr, the P-CH₃, P-OH, and P-NH₂ derivatives showed higher toxicity, whereas P-COOH exerted lower toxicity, as revealed by multiple physiological indices including growth inhibition rate, photosynthetic activity, and superoxide dismutase activity, and malondialdehyde content. Micro-PS could alleviate the toxicity of Pyr/S-Pyr toward S. costatum to varying degrees. Transcriptome analysis revealed a larger number of differentially expressed genes in the micro-PS combined with PAH treatment than in the corresponding PAH single treatment after 96 h of exposure. Furthermore, although Pyr/S-Pyr and micro-PS stress affect S. costatum to different degrees at the molecular level, genes related to metabolic pathways were primarily affected. This study provides valuable insights into the potential toxicity of S-PAHs and microplastics to marine microalgae, thereby enhancing our understanding of their environmental risks in marine ecosystems.