Sublethal impacts of fragmented polyethylene nanoplastics on Daphnia magna following chronic exposure

Abstract

Polyethylene (PE) and fragment-shaped particles are among the most prevalent polymer types and morphologies in aquatic environments. However, chronic effects of fragmented PE nanoplastics (NPs) on aquatic organisms remain largely unexplored. We evaluated the chronic toxicity (27 days) of PE NP fragments in Daphnia magna at 0.2 mg C L⁻¹ food level. Although D. magna ingested NP fragments, no significant changes in mortality were observed. However, high concentrations (10 and 100 µg mL⁻¹) of NP fragments statistically decreased the number of offspring and reduced their body length. In addition, the proportions of males and stillborn offspring were statistically increased at 10 and 100 µg mL⁻¹ of NP fragments without changing the body length of those offspring. The population growth rate of D. magna exposed to NP fragments at 1, 10, and 100 µg mL⁻¹ was statistically lower than the control. It should be noted that the concentrations tested, particularly 10 and 100 µg mL⁻¹, substantially exceed currently reported environmental NP concentrations. These findings provide chronic toxicity data for PE NP fragments that may contribute to NP risk assessment frameworks.