The sub-lethal impact of plastic and tire rubber leachates on the Mediterranean mussel Mytilus galloprovincialis

Ocean contamination by synthetic polymers can represent a risk for the fitness of marine species due to the leaching of chemical additives. This study evaluated the sub-lethal effects of plastic and rubber leachates on the mussel Mytilus galloprovincialis through a battery of biomarkers encompassing lysosomal endpoints, oxidative stress/detoxification parameters, and specific responses to metals/neurotoxicants. Mussels were exposed for 7 days to leachates from car tire rubber (CTR), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC), containing organic additives and metals in the ng-μg/L range. The leachate exposure affected general stress parameters, including the neutral lipid content (all leachates), the lysosomal membrane stability (PS, PP, PVC and CTR leachates) and lysosomal volume (PP, PVC and TR leachates). An increased content of the lipid peroxidation products malondialdehyde and lipofuscin was observed in mussels exposed to PET, PS and PP leachates, and PP, PVC and CTR leachates, respectively. PET and PP leachates increased the activity of the phase-II metabolism enzyme glutathione S-transferase, while a decreased acetylcholinesterase activity was induced by PVC leachates. Data were integrated in the mussel expert system (MES), which categorizes the organisms’ health status based on biomarker responses. The MES assigned healthy status to mussels exposed to PET leachates, low stress to PS leachates, and moderate stress to PP, CTR and PVC leachates. This study shows that additives leached from selected plastic/rubber polymers cause sub-lethal effects in mussels and that the magnitude of these effects may be higher for CTR, PVC and PP due to a higher content and release of metals and organic compounds.