To better understand the potential ecotoxicological impacts of silver nanoparticles (AgNPs) released into freshwater environments, the Daphnia magna 48‐hour immobilization test was used. The toxicities of silver nitrate, two types of colloidal AgNPs, and a suspension of AgNPs were assessed and compared using standard OECD guidelines. Also, the swimming behavior and visible uptake of the nanoparticles by Daphnia were investigated and compared. The particle suspension and colloids used in the toxicity tests were well‐characterized. The results obtained from the exposure studies showed that the toxicity of all the silver species tested was dose and composition dependent. Plus, the AgNP powder subsequently suspended in the exposure water was much less toxic than the previously prepared AgNP colloids, whereas the colloidal AgNPs and AgNO3 were almost similar in terms of mortality. The AgNPs were ingested by the Daphnia and accumulated under the carapace, on the external body surface, and connected to the appendages. All the silver species in this study caused abnormal swimming by the D. magna. Thus, according to the present results, AgNPs should be classified according to GHS (Globally Harmonized System of classification and labeling of chemicals) as “category cute 1” to Daphnia neonates, suggesting that the release of nanosilver into the environment should be carefully considered.
