Different effects of polyethylene microplastic and benzophenone-3 additive on interspecific competition of Daphnia magna and Daphnia pulex

Most ecotoxicity studies on microplastics (MPs) have focused on the single species testing, however environmentally relevant risk assessment of MPs requires different approach. The present study conducted an interspecific competition experiment between Daphnia magna and Daphnia pulex under MP fragments (MP) or MP fragments with UV filter benzophenone-3 (MP/BP-3) exposure. In MP exposure, smaller sized D. pulex was more advantageous, showing a significantly (p < 0.05) lower MP uptake and a higher population growth rate. On the other hand, in MP/BP-3 exposure, larger sized D. magna was more advantageous with a significantly (p < 0.05) lower BP-3 bioconcentration and a higher population growth rate. Transcriptomic analysis showed that expression levels of genes related to energy metabolism were significantly (p < 0.05) increased in D. pulex but significantly (p < 0.05) decreased in D. magna under MP exposure. For MP/BP-3 exposure, defense-related genes were significantly (p < 0.05) upregulated in D. magna but significantly (p < 0.05) downregulated in D. pulex. This study highlights different effects of MPs and plastic additives on interspecific interaction in the zooplankton community.