EFFECTS OF CHRONIC WATERBORNE NICKEL EXPOSURE ON TWO SUCCESSIVE GENERATIONS OF DAPHNIA MAGNA

摘要

In a 21-d chronic toxicity test in which an F_0 generation of Daphnia magna were exposed to waterborne Ni, the no-observable-effect concentration (for survival, reproduction, and growth) was 42 μg Ni L~(-1), or 58% of the measured 21-d median lethal concentration (LC50) of 71.9 μg Ni L~(-1) (95% confidence interval, 56.5-95.0). Chronic exposure to 85 μg Ni L~(-1) caused marked decreases in survival, reproduction, and growth in F_0 animals. In the F_1 generation (daphnids born of mothers from the chronically exposed F_0 generation), animals chronically exposed to 42 μg Ni L~(-1) for 11 d weighed significantly less (20%) than controls, indicating increased sensitivity of F_1 animals. Additionally, in this successive generation, significant decreases in whole-body levels of metabolites occurred following exposure to both 42 μg Ni L~(-1) (decreased glycogen and adenosine triphosphate [ATP]) and 21 μg Ni L~(-1) (decreased ATP). No significant changes were observed in whole-body total lipid, total protein, and lactate levels at any concentration. Whereas F_1 neonates with mothers that were exposed to 21 μg Ni L~(-1) showed increased resistance to acute Ni challenge, as measured by a significant (83%) increase in the acute (48-h) LC50, F_1 neonates with mothers that were exposed to 42 μg Ni L~(-1) were no more tolerant of acute Ni challenge than control animals were. Nickel accumulations in F_1 animals chronically exposed to 21 and 42 μg 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.