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The monitoring of microplastics pollution in freshwater environments trails behind its practice in marine ecosystems. We evaluated the use of the invasive zebra mussel (Dreissena polymorpha) as a potential bioindicator of microplastic litter in freshwater lakes. Samples were collected from three sites (Lovere, Costa Volpino, Castro) at the northern end of Lake Iseo (one of the major subalpine lakes in north Italy) and compared for water physicochemical parameters, biometrical features of zebra mussels, and microplastics items/specimens (color, shape, size, and chemical composition). We hypothesized that since a wastewater treatment plant (WWTP) on the Oglio River discharges into this area of the lake, the microplastics in D.polymorpha could be measured and compared in samples from the three sites at different distances from the WWTP. There was no difference in the physicochemical water parameters and biometric features between the samples from the three sites, whereas there was a significant difference in items/specimen between the sites in decreasing order (mean ± standard deviation): Costa Volpino (0.23 ± 0.43) > Lovere (0.07 ± 0.25) > Castro (0.03 ± 0.18). The chi-square test showed a significant difference in shape, color, and chemical composition frequency in the samples from the three sites. The chemical composition of the microplastics was polyethylene terephthalate (45%), nylon (20%), polypropylene (20%), polyamide resin (10%), and polyvinyl chloride (5%). Our data show that the amount of microplastics the zebra mussel accumulated was greater the closer the sampling site to the WWTP. Our findings suggest that the zebra mussel may provide a useful tool to monitor microplastics pollution in lakes.

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The most worrisome fraction within plastic pollution is that of microplastics (MP). A category of MP almost completely ignored is that of glitter. The objective of this study is to test the toxicity of nine types of glitter leachate (3 soak times: 3, 90 and 180 days) on model organisms in freshwater (Allivibrio fischeri, Raphidocelis subcapitata, Daphnia magna) and saltwater (Allivibrio fischeri, Phaeodactylum tricornutum, Paracentrotus lividus). An integrated approach was applied to obtain the percentage of ecotoxicological risk. The results show that (i) photosynthesizing primary producers are the most sensitive trophic level; (ii) algae transitioned from growth inhibition to biostimulation; (iii) D. magna showed higher sensitivity after 48 h compared to 24 h; (iv) A. fischeri responded more strongly in saltwater than in freshwater. The integrated data show a greater risk associated with the marine environment, with the highest risk for glitters that are hexagonal and composed of poly-methyl-methacrylate. Our multivariate analysis shows that the toxicity of plastic leaching is a complex phenomenon that depends on the sensitivity of the species, in some cases on the soaking time and on the medium, and is not clearly linked to the polymer type, the contact area or the colors of the particles.

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Cigarette butts (CBs) are among the dominant constituents of marine and beach litter. Few studies have been conducted, and the environmental effects of CBs on marine species are still poorly understood. This study aims to evaluate the ecotoxicological effects on marine organisms of both classic and electronic CBs. Three representative species of different trophic levels in marine ecosystems (Aliivibrio fischeri, bacteria; Phaeodactylum tricornutum, algae, primary producers; Paracentrotus lividus, echinoderms, consumers) were tested. The effects of natural ageing of CBs due to exposure to atmospheric conditions (natural sunlight vs. simulated rain) and for different times (1 vs. 2 weeks) were evaluated. The results were weighted together to obtain a synthetic hazard level to the environment (Class of Hazard) from Sediqualsoft®. Classic CBs (CCBs) performed the worst and posed a mild to moderate risk compared to electronic CBs (absent Class of Hazard). Smoked classic CBs posed a higher environmental risk than unsmoked. The highest risk was produced by classic CBs after one week of exposure in dry weather. Echinoderms and the body size reduction in normo-formed (72 h) plutei were shown to be the more sensitive organism and endpoint, respectively. We recommend the use of Sediqualsoft® software for risk assessment studies of sediments contaminated with contaminants of various types, especially in conjunction with a weight of evidence approach (WOE).