SENSITIVITY OF EARLY LIFE STAGES OF FRESHWATER MUSSELS (UNIONIDAE) TO ACUTE AND CHRONIC TOXICITY OF LEAD, CADMIUM, AND ZINC IN WATER

Toxicity of lead, cadmium, or zinc to early life stages of freshwater mussels (fatmucket, Lampsilis siliquoidea; Neosho mucket, L. rafinesqueana) was evaluated in 48-h exposures with mussel larvae (glochidia), in 96-h exposures with newly transformed (5-d-old) and two- or six-month-old juvenile mussels, or in 28-d exposures with two- or four-month-old mussels in reconstituted soft water. The 24-h median effect concentrations (EC50s) for fatmucket glochidia (>299 mu g Pb/L, >227 mu g Cd/L, 2,685 mu g Zn/L) and 96-h EC50s for two- or six-month-old fatmucket (>426 mu g Pb/L, 199 p,g Cd/L, 1,700 mu g Zn/L) were much higher than 96-h EC50s for newly transformed faunucket (142 and 298 mu g Pb/L, 16 mu g Cd/L, 151 and 175 mu g Zn/L) and Neosho mucket (188 mu g Pb/L, 20 mu g CdL, 145 mu g Zn/L). Chronic values for fatmucket were 10 mu g Pb/L, 6.0 mu g Cd/L, and 63 and 68 mu g Zn/L. When mussel data from the present study and the literature were included in updated databases for deriving U.S. Environmental Protection Agency water quality criteria, mussel genus mean acute values were in the lower percentiles of the sensitivity distribution of all freshwater species for Pb (the 26th percentile), Cd (the 15th to 29th percentile), or Zn (the 12th to 21st percentile). The mussel (Lampsilis) genus mean chronic value was the lowest value ever reported for Pb (the 9th percentile) but was near the middle of the sensitivity distribution for Cd (the 61st percentile) or Zn (the 44th percentile). These results indicate that mussels wire relatively sensitive to the acute toxicity of these three metals and to the chronic toxicity of Pb, but were moderately sensitive to the chronic toxicity of Cd or Zn compared to other freshwater species. Environ. Toxicol. Chem. 2010;29:2053-2063. (C) 2010 SETAC