title: An enriched stable-isotope approach to determine the gill-zinc binding properties of juvenile rainbow trout (Oncorhynchus mykiss) during acute zinc exposures in hard and soft waters.
abstract: The objective of the present study was to employ an enriched stable-isotope approach to characterize Zn uptake in the gills of rainbow trout (Oncorhynchus mykiss) during acute Zn exposures in hard water (approximately 140 mg/L as CaCO3) and soft water (approximately 30 mg/L as CaCO3). Juvenile rainbow trout were acclimated to the test hardnesses and then exposed for up to 72 h in static exposures to a range of Zn concentrations in hard water (0-1000 microg/L) and soft water (0-250 microg/L). To facilitate detection of new gill Zn from endogenous gill Zn, the exposure media was significantly enriched with 67Zn stable isotope (89.60% vs. 4.1% natural abundance). Additionally, acute Zn toxicity thresholds (96-h median lethal concentration [LC50]) were determined experimentally through traditional, flow-through toxicity tests in hard water (580 microg/L) and soft water (110 microg/L). Following short-term (< or =3 h) exposures, significant differences in gill accumulation of Zn between hard and soft water treatments were observed at the three common concentrations (75, 150, and 250 microg/L), with soft water gills accumulating more Zn than hard water gills. Short-term gill Zn accumulation at hard and soft water LCS0s (45-min median lethal accumulation) was similar (0.27 and 0.20 microg/g wet wt, respectively). Finally, comparison of experimental gill Zn accumulation, with accumulation predicted by the biotic ligand model, demonstrated that model output reflected short-term (<1 h) experimental gill Zn accumulation and predicted observed differences in accumulation between hard and soft water rainbow trout gills. Our results indicate that measurable differences exist in short-term gill Zn accumulation following acclimation and exposure in different water hardnesses and that short-term Zn accumulation appears to be predictive of Zn acute toxicity thresholds (96-h LC50s).
authors.affiliation: U.S. Geological Survey, Box 25046, MS 964, Denver, Colorado 80225, USA. atodd@usgs.gov
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Todd
authors.forename: Stephen
authors.initials: S
authors.lastname: Brinkman
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Wolf
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Lamothe
authors.forename: Kathleen S
authors.initials: KS
authors.lastname: Smith
authors.forename: James E
authors.initials: JE
authors.lastname: Ranville
mesh_terms: D000818:Animals; D005880:Gills / Q000187:drug effects / Q000378:metabolism*; D013058:Mass Spectrometry; D008962:Models, Theoretical; D017686:Oncorhynchus mykiss; D014874:Water Pollutants, Chemical / Q000378:metabolism* / Q000633:toxicity; D015032:Zinc / Q000378:metabolism* / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D015032:Zinc