Aquatic ecosystems are the main final destinations of the released nanomaterials into the environment. These materials may have harmful effects on the aquatic organisms and so, the study of these effects is of great importance. Aquatic nanotoxicology is the assessment of toxic effects of nanomaterials on aquatic organisms. In addition to toxic effects of nanomaterials themselves, different chemical precursors which are usually used in bottom-up or chemical approaches for production of nanomaterials may have secondary toxic effects in living organisms. In contrast, less use of chemicals in top-down or physical approaches may reduce these secondary effects. To test this hypothesis, toxic effects of two types of silver nanoparticles (AgNPs) produced by physical (top-down) and chemical (bottom-up) methods were investigated and compared on tadpole Rana ridibunda survival. The estimated 48 hour LC50 values of AgNPs produced by chemical and physical methods for tadpoles were 0.055± 0.004 and 0.296±0.085 mg/L, respectively. No observed effect concentration, lowest observed effect concentration, maximum acceptable toxicant concentration and median lethal concentration of AgNPs produced by chemical method were respectively 3.42, 4.50, 4.84 and 5.38 times less than ones produced by physical method. Therefore, the hypothesis was approved and it was revealed that AgNPs produced by chemical method are more toxic than ones generated by physical method. However, it generally seems that AgNPs regardless of the method used for their production, have toxic effects on aquatic organisms and so, inhibiting their accidental or intentional entrance into the aquatic ecosystems should be more considered.
