Effects of bioplastics and their leachates on marine bacterial communities

Biobased biodegradable plastics (bioplastics) are promising alternatives to non-degradable, fuel-based plastics. However, they often contain chemical additives that can leach into seawater, potentially impacting marine biota, though the extent of these effect is not yet fully understood. To evaluate the leaching behaviour of bioplastics in seawater and its impact on coastal surface marine bacterial communities, a 2 months microcosm experiment was conducted using seawater amended with non-aged pellets of polylactic acid (PLA), poly-hydroxybutyrate (PHB), and biodegradable commercial products: a PLA Knife and a biodegradable PLA&PHB Bag, under biotic and abiotic conditions. Chemical analysis was performed by means of Liquid Chromatography coupled to High Resolution Mass Spectrometry (LC-HRMS) in Electrospray Ionization mode in both positive and negative conditions. During the experiment, 177 compounds were tentatively identified in all samples, including PLA- and PHB-related products and plastic additives, such as plasticizers, UV-filters, flame retardants, etc., and were detected in similar proportions under abiotic and biotic processes. At the end of the experiment, bacterial production was higher in PLA treatment. Significant differences were observed in microbial community composition, with PLA degraders identified in the different plastispheres. Leachates affected differently microbial communities in the free-living, particle-attached and plastisphere, indicating a taxa-specific response. To the best of our knowledge this is the first study providing further insights into the influence of bioplastics and their leachates on marine microbial communities, contributing to our understanding of bioplastics' effects on the global oceans.