Mugilidae fish as bioindicator for monitoring plastic pollution: Comparison between a commercial port and a fishpond (north-western Mediterranean Sea).

In the last decade, interest in monitoring and managing plastic pollution has greatly increased. This study compared levels of microplastic contamination in stomachs of Mugilidae fish, suggesting this family as a target for plastic pollution monitoring in areas with different degrees of anthropisation. Two sites characterised by low and high anthropic impact, a fishpond (S'Ena Arrubia, Italy) and a port (Genoa, Italy), respectively, were compared. This study highlighted a stronger microplastic contamination in the port, with a higher percentage of fish showing the presence of microplastics and a larger polymeric variability compared to the fishpond. The microplastic number in fish from the port was higher than in the literature, but it was not significantly different from S'Ena Arrubia in terms of the microplastic percentage found in single individuals. Biomonitoring of microplastic contamination in Mugilidae fish resulted in a valid tool for the investigation of areas differently affected by human activity.

Microplastics in the abyss: a first investigation into sediments at 2443-m depth (Toulon, France).

Plastic and microplastic pollutions are known to be widespread across the planet in all types of environments. However, relatively little about microplastic quantities in the deeper areas of the oceans is known, due to the difficulty to reach these environments. In this work, we present an investigation of microplastic (<5 mm) distribution performed in the bottom sediments of the abyssal plain off the coast and the canyon of Toulon (France). Four samples of deep-sea sediment were collected at the depth of 2443 m during the sea operations carried out by the French oceanographic cruises for the KM3NeT project. The chemical and physical characterisation of the sediment was carried out, and items were extracted from sediments by density separation and analysed by optical microscope and µRaman spectroscopy. Results show microplastics in the deep-sea sediments with a concentration of about 80 particles L-1, confirming the hypothesis of microplastics spread to abyssal sediments in the Mediterranean Sea.

Considerations on salts used for density separation in the extraction of microplastics from sediments.

Environmental contamination by plastics and microplastics is a recognised problem worldwide, and it is the focus of many research teams. In the quantification of microplastics in the environment (plastic items with dimensions between 1 µm and 5 mm), the search for shared and universally recognised protocols and methodologies is still ongoing. In this study, the use of a method for extracting microplastics from marine sediments based on density separation has been considered. Fifty studies were analysed to investigate the scenario of salts exploited during microplastic extraction. The most commonly used salts are NaCl (45.6%), ZnCl2 (19.3%) and NaI (17.5%). Considerations related to cost, availability, hazards of the salts and thus the repeatability of the related extraction method are reported. In light of the findings, NaCl remains the most readily usable, economical and effective salt for the extraction of microplastics from marine sediments.

Microplastics in seawater: sampling strategies, laboratory methodologies, and identification techniques applied to port environment.

The European Interreg Italy-France 2014-2020 Maritime Project SPlasH! (Stop to Plastics in H2O!) focused on the study of microplastics (MPs) in the marine port environment to evaluate their presence, abundance, and mechanisms of diffusion to the open sea. In the framework of this project, a worldwide review of 74 studies was carried out, providing an overview of MP investigation techniques, focusing on sampling strategies, laboratory methodologies, and identification of MPs collected in seawater, and specifically evaluating their applicability to the marine port environment. Nets were the most commonly used device for MP surface sampling, but their use can be difficult in narrow spaces within the port basins, and they must be coupled to discrete sampling devices to cover all port basins. In the laboratory, density separation (NaCl, ZnCl2, NaI, sodium lauryl sulfate (SLS)), filtration (polycarbonate, polyamide, glass, cellulose, ANOPORE inorganic membrane filters), sieving, visual sorting, and digestion methods (acidic, enzymatic, alkaline, oxidative) were used to separate MPs from seawater. Digestion becomes essential with water samples with great inorganic and organic loads as deriving from a port. Although many studies are based only on visual MP identification under a microscope, analytical identification techniques unequivocally determine the particle nature and the identity of the plastic polymers and are necessary to validate the visual sorting of MPs. Fourier-transform infrared spectroscopy (FTIR) is the most used analytical identification technique.