Transcriptomic responses in Daphnia magna exposed to PLA, PBAT, and PET microplastics: Insights into different...

Microplastics are increasingly recognized as persistent pollution in freshwater ecosystems, yet their early molecular mechanism on aquatic invertebrates remains poorly characterized. In this study, we investigated the acute transcriptomic response of Daphnia magna following a 70-hour exposure to three microplastic types: polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polyethylene terephthalate (PET). Despite relatively modest numbers of differentially expressed genes, clear polymer-dependent and shared responses emerged. All three microplastics elicited a common core signature involving modulation of lipid transport, extracellular structural components, and amino acid metabolic processes, suggesting modulation of pathways linked to metabolic functions. Polymer-specific responses were also evident. Polylactic acid and PBAT jointly affected tetrapyrrole and heme biosynthetic processes, indicating potential influence on oxygen-related metabolism, while PBAT and PET shared suppression of cuticle-associated genes, consistent with modulation of structural maintenance pathways. Polylactic acid additionally affected circadian and oxidative stress-related processes, whereas PET modulated immune-related signalling, including toll-like receptor pathways. These findings demonstrate that polymer type influences distinct biological processes in D. magna, highlighting the importance of polymer chemistry in shaping organismal responses to microplastic exposure. This study also accentuates the value of transcriptomic profiling for identifying pathway-level responses that may not be captured by conventional endpoints.