Influence of water quality on silver toxicity to rainbow trout (Oncorhynchus mykiss), fathead minnows (Pimephales promelas), and water fleas (Daphniamagna)
Dj. Karen et al., Influence of water quality on silver toxicity to rainbow trout (Oncorhynchus mykiss), fathead minnows (Pimephales promelas), and water fleas (Daphniamagna), ENV TOX CH, 18(1), 1999, pp. 63-70
Toxicity bioassays were conducted to quantify water quality conditions unde
r which silver, as silver nitrate, is toxic to Oncorhynchus mykiss, Pimepha
les promelas, and Daphnia magna. Bioassays for P. promelas and D. magna wer
e conducted as static replacement tests, whereas a flow-through bioassay sy
stem was modified and used for O. mykiss. Results from 96-h toxicity bioass
ays for O. mykiss indicated that chloride, hardness, and dissolved organic
carbon (DOC) protected against silver toxicosis, with DOC affording the hig
hest protective effects. For P. promelas and D. magna, little protection wa
s provided by increased CaCO3 alone, whereas DOC had a major ameliorating i
nfluence on measured silver toxicity. Lower concentrations of chloride (<20
mg/L) had little effect on reducing silver nitrate toxicity. Dissolved org
anic carbon was more important than hardness for predicting the toxicity of
ionic silver in natural waters to O. mykiss, P. promelas, and D. magna. Si
milarly, DOC significantly reduced silver nitrate toxicity to trout, wherea
s Cl- and hardness had only a minor protective effect. However, Cl-/DOC mix
tures showed a greater-than-additive protective effect. Thus, we suggest th
at incorporating an organic carbon coefficient into the silver criterion eq
uation will enhance the criterion values for site specificity.