Effect of UV-weathering on chronic toxicity of biodegradable mulch film microplastics to Daphnia magna: Particle versus extract exposure

초록

Biodegradable mulch films are increasingly applied as sustainable alternatives to conventional plastics. However, their ecological hazards following environmental fragmentation and aging remain insufficiently understood. In particular, how ultraviolet (UV) weathering alters particle-associated and chemically mediated toxicity of biodegradable mulch films microplastics is unclear. Here, we investigated the chronic effects (16 days) of pristine and UV-weathered mulch film microplastics (PMF and UMF, respectively) and their corresponding methanol extracts (EXP and EXU, respectively) on Daphnia magna. By integrating life-history traits, biochemical energy reserves, and transcriptional responses, we disentangled particle and extract exposure. Particle exposure was associated with mortality and broader life-history impairment in D. magna, whereas extract exposure primarily affected somatic growth and reproduction without affecting survival. UV-weathering reduced particle size and increased internal particle burden; however, UMF exposure was associated with comparatively reduced organism-level impairment relative to PMF. Under extract exposure, organism-level responses were broadly comparable between EXP and EXU, whereas EXU exhibited comparatively stronger transcriptional responses related to mitochondrial and carbohydrate metabolism-associated genes. Overall, the effects of UV-weathering were endpoint-dependent rather than reflecting a uniform increase or decrease in toxicity. Instead, UV-weathering modified biological responses differently between particle and extract exposure conditions. These findings highlight the importance of exposure-specific assessment when evaluating the environmental hazards of biodegradable microplastics

키워드