Pollution by anthropogenic microfibers in North-West Mediterranean Sea and efficiency of microfiber removal by a wastewater treatment plant.

The widespread pollution from the release of microfibers is an emerging concern as they are a potential threat to the environment. Their identification in samples in terms of quantity and pathways remain a challenge as contamination can be a major source of error. A systematic study of synthetic microfibers (MFs) has been carried out in different environmental compartments of an urban area and in the surface waters of the northwestern Mediterranean. The quantity, size and type of polymer of MFs were recorded in air, in waste water from a domestic washing machine, at the inlet and outlet of the Haliotis urban wastewater treatment plant (WWTP) in Nice (Provence Alpes Côte-d'Azur, France) and in a variety of coastal and offshore areas. The results showed that MFs released by clothes during washing (on average of 13 × 106 MFs per m3) are an important emitter of microplastics. Despite its high removal efficiency (87.5% to 98.5%) by Haliotis, a large number of MFs, estimated at 4.3 billion, enter the marine environment daily from the treatment plant. The attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterization of the raw materials showed that 14 to 50% of fibers are synthetic, mostly polyester and polyamide, the remaining 35 to 72% being natural polymers (cotton, wool) or manufactured by processing natural polymers (especially cellulose). MFs were found in all environmental compartments studied and appear to be widespread in coastal and offshore surface waters with concentrations varying from 2.6 × 103 to 3.70 × 104 m-3. The sources of MFs in the marine environment are multiple, with laundry fibers discharges from WWTP and the atmospheric transport of urban fibers are among the main pathways.

Evidence of niche partitioning among bacteria living on plastics, organic particles and surrounding seawaters.

Plastic pollution is widespread in ocean ecosystems worldwide, but it is unknown if plastic offers a unique habitat for bacteria compared to communities in the water column and attached to naturally-occurring organic particles. The large set of samples taken during the Tara-Mediterranean expedition revealed for the first time a clear niche partitioning between free-living (FL), organic particle-attached (PA) and the recently introduced plastic marine debris (PMD). Bacterial counts in PMD presented higher cell enrichment factors than generally observed for PA fraction, when compared to FL bacteria in the surrounding waters. Taxonomic diversity was also higher in the PMD communities, where higher evenness indicated a favorable environment for a very large number of species. Cyanobacteria were particularly overrepresented in PMD, together with essential functions for biofilm formation and maturation. The community distinction between the three habitats was consistent across the large-scale sampling in the Western Mediterranean basin. 'Plastic specific bacteria' recovered only on the PMD represented half of the OTUs, thus forming a distinct habitat that should be further considered for understanding microbial biodiversity in changing marine ecosystems.