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首页> 外文期刊>Environmental Science & Technology: ES&T >Mechanisms of acute and chronic waterborne nickel toxicity in the freshwater cladoceran, Daphnia magna
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Mechanisms of acute and chronic waterborne nickel toxicity in the freshwater cladoceran, Daphnia magna

机译：Mechanisms of acute and chronic waterborne nickel toxicity in the freshwater cladoceran, Daphnia magna

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We present evidence that Mg2+ antagonism is one mechanism for acute toxicity of waterborne Ni to Daphnia magna. Acutely, adult D. magna were exposed to either control or 694 mug Ni L-1 as NiSO4 in moderately soft water (45 mg L-1 as CaCO3; background Ni congruent to 1 mug Ni L-1) for 48 h without feeding. Chronically, adults were exposed to either control or 131 mug Ni L-1 for 14 days (fed exposure). These concentrations were approximately 65 and 12, respectively, of the measured 48-h LC50 (1068 mug Ni L-1) for daphnid neonates in this water quality. The clearest effect of Ni exposure was on Mg2+ homeostasis, as wholebody Mg2+ was significantly decreased both acutely and chronically by 18. Additionally, unidirectional Mg2+ uptake rate (measured with the stable isotope Mg-26) was significantly decreased both acutely and chronically by 49 and 47, respectively, strongly suggesting that Ni is toxic to D. magna due at least in part to Mg2+ antagonism. No impact was observed on the whole-body concentrations or unidirectional uptake rates of Ca2+ during either acute or chronic Ni exposure, while only minor effects were seen on Na+ and Cl- balance. No acute toxic effect was seen on respiratory parameters, as both oxygen consumption rate 002) and whole-body hemoglobin concentration (Hb) were conserved. Chronically, however, Ni impaired respiratory function, as both MO2 and Hb were significantly reduced by 31 and 68, respectively. Acutely, Ni accumulation was substantial, rising to a plateau between 24 and 48 h of approximately 15 mug g(-1) wet weight-an increase of approximately 25-fold over control concentrations. Mechanisms of acute toxicity of Ni in D. magna differ from those in fish; it is likely that such mechanistic differences also exist for other metals. References: 44

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