Microplastic pollution affect sediment microbial communities structure: evidences from Volturno River (Southern Italy)

For the first time, we explored sources, abundance, and ecological implications of microplastics (MPs) pollution in the one of the main river of Southern Italy (Volturno) by investigating MPs concentration levels of sediments collected along the watercourse. Samples were analysed by the Polymer Identification and Specific Analysis (PISA) protocol to quantify the total mass of individual polymer types: after sieving at <2 mm the sediments were sequentially extracted with selective organic solvents and the polymer classes polystyrene (PS), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polycarbonates (PC), Nylon 6 (PA6) and Nylon 6,6 (PA66) were quantified by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and HPLC. This method enables an accurate and specific quantification of micron and submicron scale polymers. Furthermore, in the light of current evaluations about the impact produced by anthropogenic activities in natural habitats through the study of their microbial diversity, we investigated the 16S metagenomics of Volturno river using next generation sequencing in Ion Torrent™, to explore bacterial taxonomy and ecological dynamics of sediment samples. We detected MPs in all samples taken from the study area. Total MPs concentration ranged from 1.05 to 14.55 ppm and identify two distinct data population: high-MPs contaminated and low-MPs contaminated sediments. Overall PP and PET were the dominant polymer types. According to the Polymer Hazard Index (PHI), the risk of MPs pollution of the analysed sediments was categorized as Hazard level III/IV (corresponding to Danger category). Metagenomic data revealed that the presence of MPs significantly affects bacterial taxa abundance, evidencing Flavobacteraceae and Nocardiaceae, known to degrade polymeric substances in high-MPs contaminated sediments. This study provide new insights of ecological relevance related to MPs pollution and suggests priorities for the management of one of the main Southern Italy’s river. In addition, the study advise that monitoring programs of river ecosystems should address also bacterial communities.