Polystyrene microplastics alleviate adverse effects of benzo[a]pyrene on tissues and cells of the marine mussel, Mytilus galloprovincialis

As two major ubiquitous pollutants, microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) coexist in the marine environment. However, the role of MPs in altering the toxicity of PAHs to marine organisms is poorly understood. We therefore investigated the accumulation and toxicity of benzo[a]pyrene (B[a]P, 0.4 nM), in the marine mussel Mytilus galloprovincialis over a 4-day of exposure with or without the presence of 10 mu m poly-styrene microplastics (PS MPs) (10 particles/mL). The presence of PS MPs significantly decreased B[a]P accu-mulation in soft tissues of M. galloprovincialis by approximately 6.7%. Single exposure of PS MPs or B[a]P decreased the mean epithelial thickness (MET) of digestive tubules and enhanced reactive oxygen species (ROS) levels in haemolymph, while upon co-exposure the adverse impacts were alleviated. Real-time q-PCR results showed that most selected genes involved in stress response (FKBP, HSP90), immune (MyD88a, NF-Kappa B) and detoxification (CYP4Y1) were induced for both single exposure and co-exposure. The co-presence of PS MPs down-regulated the mRNA expression of NF-Kappa B in gills compared with of B[a]P alone. The uptake and toxicity reductions of B[a]P might result from the decrease of its bioavailable concentrations caused by the adsorption of B[a]P by PS MPs and the strong affinity of B[a]P to PS MPs. Adverse outcomes for the co-existence of marine emerging pollutants under long-term conditions remain to be further validated.

Automated summary

The presence of microplastics (MPs) significantly reduced the accumulation of benzo[a]pyrene (B[a]P) in the soft tissues of Mytilus galloprovincialis. The adverse impacts of digestive tubule thinning and increased reactive oxygen species (ROS) levels were alleviated when the mussels were exposed to both MPs and B[a]P. The co-presence of MPs also down-regulated the mRNA expression of NF-Kappa B in gills compared to B[a]P alone.