Acute co-exposure to microbeads and cadmium enhances accumulation and alters plasma biochemical markers and stress indicators in Korean rockfish, Sebastes schlegeli

Microplastics (MPs), including microbeads (MBs) and heavy metals such as cadmium (Cd), are persistent marine pollutants that can interact synergistically, with MPs facilitating metal adsorption and transportation. Korean rockfish, an important commercial species, inhabits coastal waters and is susceptible to various external pollutants. In this study, we aimed to assess the effects of co-exposure to MBs and Cd on the accumulation of these contaminants and physiological stress responses in Korean rockfish. Juvenile Korean rockfish were exposed to either a control, single treatments of MBs (5 beads/L [MB5] or 50 beads/L [MB50]) or Cd (0.2 mg/L [Cd0.2] or 0.4 mg/L [Cd0.4]), or their combined treatments (MB5 + Cd0.2, MB5 + Cd0.4, MB50 + Cd0.2, and MB50 + Cd0.4) for 5 days. After exposure, MBs and Cd accumulations in the gill and intestine were significantly higher in the MB50 + Cd0.4 than those in the other combined-exposure groups at all time points (p < 0.05 for all). Compared with the control treatment, the combined treatments significantly increased the levels of plasma glucose, aspartate transaminase, and alanine transaminase, and mRNA expression of heat shock protein 70 and metallothionein in the liver (p < 0.05 for all), with the MB50 + Cd0.4 treatment exhibiting the highest values for most parameters. Comet assays also showed significantly increased DNA damage in combined-exposure groups compared with those in single-exposure groups (p < 0.05 for all). These findings highlight that co-exposure to MBs and Cd enhances Cd bioaccumulation, toxicity, and DNA damage, underscoring the risks associated with marine pollutant mixtures and their implications for environmental monitoring and coastal management.