Adsorption of bisphenol S onto polyethylene terephthalate microfibers and their combined effects in oysters

Microplastics are widespread in global aquatic ecosystems and have become key vectors for transporting environmental contaminants. In this study, we investigated the adsorption behavior of bisphenol S (BPS) onto polyethylene terephthalate (PET) fibers under laboratory conditions. The adsorption capacity of PET fibers for BPS was concentration-dependent and reached equilibrium after approximately 48 h. Adsorption increased with rising temperatures from 10 °C to 30 °C, and decreased with increasing salinity from 0 to 32. Both PET fibers and BPS accumulated significantly in oysters after one hour exposure. The concentration of PET fibers in oysters co-exposed to PET and BPS was significantly higher than that in oysters exposed to PET alone between 6 and 24 h of exposure. Additionally, after 168 h, BPS levels in both gills and gonads of the BPS-only group were 1.1 to 1.7 times higher than those in the multiple co-exposure groups, suggesting that combined exposures with PET fibers reduce BPS accumulation compared to BPS exposure alone. RNA-seq analysis revealed that differentially expressed genes in the combined exposure group were mainly enriched in biological processes related to oxidative stress, lipid metabolism, immune response, and energy production. Furthermore, compared to the BPS-only group, the number of differentially expressed genes associated with neurogenesis and reproduction was reduced under combined exposure. These findings suggest a potential antagonistic interaction between PET fibers and BPS in oysters.