The aim of this study was to determine and compare the toxicity of silver nanoparticles (AgNPs) and silver ions (derived from AgNO3) in two different larval stages of brine shrimp. For this purpose the instar I and II stages of Artemia salina were acutely exposed to Ag ions or NPs for 48 hours and their immobilization rates were assessed according to ISO TS 20787. AgNPs were well characterized with TEM, DLS, and UV-Vis spectrometer. Potassium dichromate (K2Cr2O7) was selected as positive control. All experiments were conducted in 10 mL artificial sea water (ASW) poured to 6-well plates, under photoperiod of 16 h light:8 h dark, temperature of 30 °C and salinity of 35 ‰. According to the results, a concentration-dependent effect of silver ions and NPs was observed on immobilization rate of A. salina (instar I and II). In general, the toxic effect of different concentrations of Ag ions and NPs on second naupliar stage was significantly higher than first naupliar stage (P<0.05). This is while sensitivity of both naupliar stages to the positive control was approximately the same. The median effective concentrations (EC50s) of AgNPs, Ag ions and Cr ions were calculated as 47.06±9.76, 102.88±3.45, and 9.56±0.12 for instar stage I and 9.79±0.52, 3.32±0.89, and 10.91±0.81 for instar II, respectively. This results show that toxicity of silver ions to instar I is less than AgNPs, while in the case of instar II, silver ions were more toxic than silver nanoparticles.
