Polylactic Acid Bioplastics (PLA BPs): A Threat to the Reproductive Health of the Mediterranean Mussel Mytilus galloprovincialis

In the context of the global transition towards a more sustainable economy, the use of bioplastics (BPs) is rapidly increasing across several sectors, including industry, medicine and cosmetics. Among BPs, polylactic acid (PLA) is the “polymer of the 21st century”. Because of its wide use and slow degradation capacity, it can be found in various aquatic matrices, causing potential health concerns for biota. This work evaluated the influence of environmental concentrations (0.5 µg/mL) of PLA BPs on the reproductive health of the Mediterranean mussel Mytilus galloprovincialis, following a short-term exposure of 7 days. This resulted in an early spawning event from the gonads of both sexes, accompanied by an intense hemocyte recall, suggesting the onset of a pro-inflammatory condition. Alterations in the bioenergetic pathway affecting glycogen reserves as an adaptive strategy were revealed in both sexes by proton Nuclear Magnetic Resonance (1H NMR)-based metabolomics, in addition to disorders in the redox balance. This latter was more evident in males, as confirmed by the increased activity of antioxidant (catalase) and detoxifying (glutathione S-transferase) enzymes, while no lipid peroxidation occurred. Overall, this study highlights the threat of PLA BPs on the reproductive system of non-target organisms, raising further questions on the reproductive fitness and survival of a species with high ecological and economic value.