Section 11
Chapter 10,968

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

Pane, E.F.; Smith, C.; Mcgeer, J.C.; Wood, C.M.

Environmental Science and Technology 37(19): 4382-4389


ISSN/ISBN: 0013-936X
PMID: 14572089
DOI: 10.1021/es034317l
Accession: 010967667

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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 [mu]g Ni L-1 as NiSO4 in moderately soft water (45 mg L-1 as CaCO3; background Ni [similar or equal to] 1 [mu]g Ni L-1) for 48 h without feeding. Chronically, adults were exposed to either control or 131 [mu]g Ni L-1 for 14 days (fed exposure). These concentrations were approximately 65% and 12%, respectively, of the measured 48-h LC50 (1068 [mu]g 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 26Mg) 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 ([overhead single dot]O2) and whole-body hemoglobin concentration ([Hb]) were conserved. Chronically, however, Ni impaired respiratory function, as both [overhead single dot]O2 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 [mu]g g-1 wetweightan 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.

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