title: Effects of water chemistry variables on gill binding and acute toxicity of cadmium in rainbow trout (Oncorhynchus mykiss): A biotic ligand model (BLM) approach.
abstract: This study investigated the short-term (3 h) cadmium binding characteristics of the gills, as well as the influence of various water chemistry variables [calcium, magnesium, sodium, pH, alkalinity and dissolved organic carbon (DOC)] on short-term gill accumulation and acute toxicity of cadmium in juvenile freshwater rainbow trout. The cadmium binding pattern revealed two types of cadmium binding sites in the gill: (i) saturable high affinity sites operating at a low range of waterborne cadmium concentration, and (ii) non-saturable low affinity sites operating at a higher range of cadmium concentration. Among the water chemistry variables tested, only calcium and DOC significantly reduced both gill accumulation and toxicity of cadmium. Interestingly, alkalinity (15-90 mg L(-1) as CaCO(3)) did not influence the gill cadmium accumulation but a significant increase in toxicity was recorded at a higher alkalinity level (90 mg L(-1)). Affinity constants (log K) for binding of competing cations (Cd(2+) and Ca(2+)) to the biotic ligand and for binding of Cd(2+) to DOC were derived separately from the 3 h gill binding tests and the 96 h toxicity tests. In general, the values agreed well, indicating that both tests targeted the same population of high affinity binding sites, which are likely Ca(2+) uptake sites on the gills. These parameters were then incorporated into a geochemical speciation model (MINEQL+) to develop a biotic ligand model for predicting acute toxicity of cadmium in trout. The model predictions exhibited a good fit with the measured toxicity data except for high alkalinity and pH.
authors.affiliation: Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E2. som.niyogi@usask.ca
authors.forename: Som
authors.initials: S
authors.lastname: Niyogi
authors.forename: Rebecca
authors.initials: R
authors.lastname: Kent
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
mesh_terms: D000818:Animals; D001665:Binding Sites; D019256:Cadmium Chloride / Q000378:metabolism / Q000633:toxicity*; D002118:Calcium / Q000737:chemistry; D002119:Calcium Carbonate / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005618:Fresh Water / Q000737:chemistry*; D005880:Gills / Q000187:drug effects* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007928:Lethal Dose 50; D008024:Ligands; D008274:Magnesium / Q000737:chemistry; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D009930:Organic Chemicals / Q000737:chemistry; D015203:Reproducibility of Results; D012964:Sodium / Q000737:chemistry; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000633:toxicity*
chemical_list: D008024:Ligands; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D012964:Sodium; D002119:Calcium Carbonate; D008274:Magnesium; D019256:Cadmium Chloride; D002118:Calcium