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Size-dependent chronic toxicity of fragmented polyethylene microplastics to Daphnia magna
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Researchers tested the long-term effects of irregularly shaped polyethylene microplastic fragments on the freshwater organism Daphnia magna over 21 days. They found that fragmented microplastics were ingested at much higher rates and caused more harm to reproduction and survival than smooth, round plastic beads of similar size, suggesting particle shape matters for toxicity.
Fragmented microplastics (MPs) are emerging contaminants in freshwater environments; however, long-term assessment of their toxicity remains limited. This study aimed to evaluate and compare the chronic toxicity (21 d) of synthesized polyethylene MP fragments and commercial polyethylene MP beads to Daphnia magna. Ingestion of small- and large-sized MP fragments (17.23 ± 3.43 and 34.43 ± 13.09 μm, respectively) by D. magna was significantly (p < 0.05) higher, by 8.3 and 5.2 times, respectively, than that of MP beads (39.54 ± 9.74 μm). The survival of D. magna exposed to small- and large-sized MP fragments (20 and 60%, respectively) was significantly (p < 0.05) lower than that of individuals exposed to MP beads (90%). In particular, small-sized MP fragments significantly (p < 0.05) reduced algal feeding (from 95% to 76%), body length (from 4.20 mm to 3.98 mm), and the number of offspring (from 109 to 74) in D. magna, when compared with MP beads, likely due to their longer retention time and greater interference in the digestive tract. These findings suggest that fragmentation of MPs into μm-scale particles can pose a significant ecological risk to aquatic organisms; moreover, further studies are required to identify the underlying toxicity mechanism.
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Researchers studied how the water flea Daphnia magna ingests and excretes polyethylene microplastics of different shapes and sizes. They found that irregular-shaped fragments were ingested differently than regular beads, and that neither type caused acute mortality at tested concentrations — but the study raises questions about chronic effects in this key freshwater species.
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Researchers systematically tested how the shape, size, and material of microplastic particles affect the water flea Daphnia magna by comparing polystyrene particles to non-plastic control particles with similar properties. They found that small polystyrene beads and fragments caused harmful effects on reproduction and body shape, while none of the non-plastic control particles caused any damage. The study suggests that the toxic effects are specific to the plastic polymer itself, not simply a result of ingesting small particles.
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Researchers studied how the shape of polystyrene microplastics affects toxicity in the water flea Daphnia magna, comparing irregular fragments to smooth beads. The study found that fragment-shaped microplastics were more toxic than spherical beads, triggered stronger reactive oxygen species production, and induced different gut microbiota changes, suggesting that particle shape is an important factor in microplastic toxicity.
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