Abstract
The widespread ocean contamination by plastic materials is cause of increasing concerns on the potential detrimental consequences they might produce on marine ecosystems. Although many recent studies addressed ingestion and effects of micro/nanoplastics on most marine taxa, the risks posed by leached chemical additives have so far been overlooked. This study aimed at assessing the impact of aqueous leachates from car tire rubber (CTR), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC) on the Mediterranean mussel Mytilus galloprovincialis. Endpoints encompassed early life stages parameters and cellular / physiological biomarkers measured following in vitro and in vivo assays. The exposure of mussel gametes to concentrations ranging from 0.6 to 100% of all tested leachates resulted in a dose-dependent and significant (p < 0.05 vs. control) decrease of the fertilization success, with CTR leachate leading to the lowest effective concentration (EC50) of 36.4%. Highly significant effects were also induced by all leachates on the mussel embryo-larval development, with effects ranked as CTR > PVC > PP > PS > PET and EC50 values in the range of 2.2 (CTR) - 96.8% (PET). Among tested leachates, only those from CTR and PVC were found to significantly affect the motility and survival of mussel D-shaped larvae, with EC50 values comprised in the range of 18-25% and 55- 59%, respectively. Leachates also affected cellular endpoints of general stress, as the lysosomal membrane stability in adult mussel hemocytes, which decreased significantly following the in vitro exposure to PS, PP, PVC and CTR leachates and the (7-day) in vivo exposure to PP, PVC and CTR leachates. To screen for potential relationships between the leachates toxicity and chemical composition, all leachates were analyzed through GC-MS, which revealed the occurrence of plasticizers, antioxidants, antimicrobials, lubricants, vulcanizers and metals at concentrations spanning from hundreds of ng/L to thousands of μg/L depending on the tested polymers. Overall, this study provides clear evidence of toxicity of plastic leachates on the mussel ontogeny and cellular fitness, urging the need for a better understanding of their overall impact on marine ecosystems.