Distribution and Effects of Model Palladium-Doped Nanoplastics in the Marine Mussel Mytilus galloprovincialis

While nanoplastics (NPs, <1 µm) concentration is anticipated to increase in the marine environment, the analytical tools for NP quantification and data on their impacts are still scarce. This work aimed to expand knowledge regarding bioaccumulation and effects of NPs on the sentinel organism Mytilus galloprovincialis. For this, mussels were dietarily exposed for 7 days to model palladium-doped-polystyrene NPs (Pd-PS NPs) of 142.6 ± 1.0 nm at 1 × 10⁹ Pd-PS NPs/mL. ICP-MS analysis on water samples showed that after one day of exposure no Pd was detected suggesting that mussels cleared the NPs. After 7 days of exposure, 14% of the Pd introduced in the tanks was found in feces. Less than 0.02% passed into the hemolymph of mussels and consequently, no responses were observed on hemocytes. Approximately 1% of the Pd was found in soft tissues. This could be linked to the significantly higher prevalence of digestive tubule atrophy observed in exposed mussels in comparison to controls. No effects were observed at the whole organism level. In conclusion, mussels were able to uptake and to eliminate Pd-PS NPs through feces. Whether longer exposures could cause a significant accumulation of NPs and produce associated biological effects remains to be studied.