Plastic pollution is a critical environmental concern and comprises the majority of
anthropogenic debris in the ocean, including macro, micro, and likely nano-scale (less
than 100 nm in at least one dimension) plastic particles. While the toxicity of macroplastics
and microplastics is relatively well studied, the toxicity of nanoplastics is largely
uncharacterized. Here, fluorescent polystyrene nanoparticles (PS NPs) were used to
investigate the potential toxicity of nanoplastics in developing zebrafish ( Danio
rerio ), as well as characterize the uptake and distribution of the particles within
embryos and larvae. Zebrafish embryos at 6 h post-fertilization (hpf) were exposed
to PS NPs (0.1, 1, or 10 ppm) until 120 hpf. Our results demonstrate that PS NPs accumulated
in the yolk sac as early as 24 hpf and migrated to the gastrointestinal tract, gallbladder,
liver, pancreas, heart, and brain throughout development (48 hpf-120 hpf). Accumulation
of PS NPs decreased during the depuration phase (120 hpf-168 hpf) in all organs, but
at a slower rate in the pancreas and gastrointestinal tract. Notably, exposure to
PS NPs did not induce significant mortality, deformities, or changes to mitochondrial
bioenergetics, but did decrease the heart rate. Lastly, exposure to PS NPs altered
larval behavior as evidenced by swimming hypoactivity in exposed larvae. Taken together,
these data suggest that at least some nanoplastics can penetrate the chorion of developing
zebrafish, accumulate in the tissues, and affect physiology and behavior, potentially
affecting organismal fitness in contaminated aquatic ecosystems.