Abstract Environmental pollutants can profoundly influence host-associated microbiomes, with cascading effects on host health and susceptibility to disease. Here, we investigated whether nanoplastic particles (NPs), a pervasive contaminant, influence host-parasite interaction by altering the microbiome of the water flea Daphnia magna. Microbiomes from NP-exposed and control Daphnia donors were transplanted to axenic Daphnia recipients, which were subsequently challenged with the fungal parasite Australozyma monospora sp. nov. Host and parasite fitness were then compared across treatments. NP exposure induced marked shifts in bacterial community structure and increased microbial diversity in donor microbiomes. These shifts persisted after transplantation, with recipient microbiomes remaining distinct from controls throughout the host lifespan, despite the absence of direct NP exposure. Microbiome shifts associated with NP exposure corresponded to elevated parasite reproduction and reduced host fecundity, while host survival was unaffected. Our findings demonstrate that NP pollution can indirectly compromise host health by reshaping microbial communities, highlighting microbiome-mediated pathways as important mechanisms through which emerging pollutants may shape ecological and evolutionary dynamics.
Villegas et al. (Sat,) studied this question.