Evaluation of cross-generational exposure to microplastics and co-occurring contaminants on embryonic and larval behavior in fathead minnows, <i>Pimephales promelas</i>

Microplastics (MPs) are ubiquitous in freshwater systems, and understanding their effects on aquatic organisms is increasingly important. Microplastics also have unique surface properties that allow them to act as vectors for common environmental pollutants, such as endocrine-disrupting chemicals (EDCs), and can serve as an additional route of exposure to those contaminants. However, few studies have considered the cross-generational effects of microplastics on early life-stage behaviors in aquatic vertebrates. In this study, adult fathead minnows, <i>Pimephales promelas,</i> were exposed to microplastics alone (MP_Virgin) or in association with one of two environmentally relevant concentrations of 17 <i>α</i>-ethinyl estradiol (low; MP_{EE2 10} and high; MP_{EE2 50}) for 30 days and then were allowed to spawn. Embryonic activity was assessed for F1 offspring of MP-exposed adults at 4 days post-fertilization. After hatching, half of these larvae received continued exposure to MPs for 21 days, and larvae were tested in open-field swimming trials for swimming performance and space use at 14 and 21 days post-hatch. Before hatching, MP_{EE2 10} F1 individuals showed reduced activity compared to other groups. After hatching, larvae from MP-exposed parents were more active than control larvae, but no changes in space use were observed. Evidence was limited for the effects of continued MP exposure on larvae after hatching, or combined effects of MPs and EE2. These results indicate that parental exposure to MPs induces subtle, sublethal effects on embryos and larvae that have the potential to affect individual fitness.