Toxicity of sodium molybdate and sodium dichromate to Daphnia magna Strausevaluated in acute, chronic, and acetylcholinesterase inhibition tests

As a result of a widespread application in numerous industrial processes, c hromium is a contaminant of many environmental systems. Chromium and their compounds are toxic to both invertebrates and vertebrates and, for this rea son, there has been a search for suitable and less toxic alternatives. Moly bdenum compounds have been studied as alternative to chromium compounds for some industrial applications. The toxicity of chromium is well known but t he effects of molybdenum and molybdenum mining on natural populations and c ommunities of freshwater invertebrates have not often been studied. However , chromium, and molybdenum (and their compounds) are included in the same l ist (List II) of European Union dangerous substances. In this study, the ac ute and chronic effects of sodium molybdate and sodium dichromate to Daphni a magna Straus were evaluated. Furthermore, in vitro and in vivo effects of these two metals on acetylcholinesterase (AChE) activity of D. magna Strau s were investigated. LC50 values determined at 48 h were 0.29 and 2847.5 mg L-1 for chromium (as sodium dichromate) and molybdenum (as sodium molybdat e), respectively. No significant in vitro effects of both metals on AChE we re found. However, both toxicants inhibited AChE in vivo at concentrations under the respective 48-h LC50 values. Both sodium dichromate and sodium mo lybdate inhibited the reproduction and growth of D. magna, but the concentr ations inducing significant effects were different for the two chemicals. S odium molybdate had significant lower toxicity to D. magna Straus than sodi um dichromate, (C) 2000 Academic Press.