Effects of chronic waterborne nickel exposure on two successive generations of Daphnia magna.

In a 21-d chronic toxicity test in which an F0 generation of Daphnia magna were exposed to waterborne Ni, the no-observable-effect concentration (for survival, reproduction, and growth) was 42 microg Ni L(-1), or 58% of the measured 21-d median lethal concentration (LC50) of 71.9 microg Ni L(-1) (95% confidence interval, 56.5-95.0). Chronic exposure to 85 microg Ni L(-1) caused marked decreases in survival, reproduction, and growth in F0 animals. In the F1 generation (daphnids born of mothers from the chronically exposed F0 generation), animals chronically exposed to 42 microg Ni L(-1) for 11 d weighed significantly less (20%) than controls, indicating increased sensitivity of F1 animals. Additionally, in this successive generation, significant decreases in whole-body levels of metabolites occurred following exposure to both 42 microg Ni L(-1) (decreased glycogen and adenosine triphosphate [ATP]) and 21 microg Ni L(-1) (decreased ATP). No significant changes were observed in whole-body total lipid, total protein, and lactate levels at any concentration. Whereas F1 neonates with mothers that were exposed to 21 microg Ni L(-1) showed increased resistance to acute Ni challenge, as measured by a significant (83%) increase in the acute (48-h) LC50, F1 neonates with mothers that were exposed to 42 microg Ni L(-1) were no more tolerant of acute Ni challenge than control animals were. Nickel accumulations in F1 animals chronically exposed to 21 and 42 microg Ni L(-1) were 11- and 18-fold, respectively, above control counterparts. The data presented suggest that chronic Ni exposure to two successive generations of D. magna lowered the overall energy state in the second generation. Whereas the quantity of neonates produced was not affected, the quality was; thus, environmentally meaningful criteria for regulating waterborne Ni concentrations in freshwater require consideration of possible multigenerational effects.