Toxicity of silver sulfide-spiked sediments to the freshwater amphipod (Hyalella azteca)

Natural freshwater sediments were spiked in the laboratory with silver sulfide (Ag2S), and semistatic toxicity tests were conducted with a series of sediment silver (Ag) concentrations ranging from 1.27 to 753.3 mg/kg of sediment. Water was added to glass beakers containing either the Ag2S-amended or the control sediment. Each of the Ag2S-amended and control sediments was tested in replicates of eight. Ten juvenile Hyalella azteca were added to each beaker at test start. The overlying water was renewed twice daily. The 10-d 50% lethal concentration value for Ag as Ag2S for H. azteca was determined to be >753.3 mg/kg, the highest analyzed concentration tested. There were no statistically significant differences in survival rates of H. azreca exposed to any of the Ag2S-amended sediments when compared to the control. In addition, there were no concentration-response trends for mean survival or average dry weight data from this study, indicating that this form of silver was not bioavailable under these conditions.