Contaminant Sensitivity of Freshwater Mussels INTRA- AND INTERLABORATORY VARIABILITY IN ACUTE TOXICITY TESTS WITH GLOCHIDIA AND JUVENILES OF FRESHWATER MUSSELS (UNIONIDAE)

Abstract —The present study evaluated the performance and variability in acute toxicity tests with glochidia and newly transformedjuvenile mussels using the standard methods outlined in American Society for Testing and Materials (ASTM). Multiple 48-h toxicitytests with glochidia and 96-h tests with juvenile mussels were conducted within a single laboratory and among five laboratories.All tests met the test acceptability requirements (e.g., 90% control survival). Intralaboratory tests were conducted over twoconsecutive mussel-spawning seasons with mucket ( Actinonaias ligamentina ) or fatmucket ( Lampsilis siliquoidea ) using copper,ammonia, or chlorine as a toxicant. For the glochidia of both species, the variability of intralaboratorymedianeffectiveconcentrations(EC50s) for the three toxicants, expressed as the coefficient of variation (CV), ranged from 14 to 27% in 24-h exposures and from13 to 36% in 48-h exposures. The intralaboratory CV of copper EC50s for juvenile fatmucket was 24% in 48-h exposures and13% in 96-h exposures. Interlaboratory tests were conducted with fatmucket glochidia and juveniles by five laboratories usingcopper as a toxicant. The interlaboratory CV of copper EC50s for glochidia was 13% in 24-h exposures and 24% in 48-h exposures,and the interlaboratory CV for juveniles was 22% in 48-h exposures and 42% in 96-h exposures. The high completion success andthe overall low variability in test results indicate that the test methods have acceptable precision and can be performed routinely.