title: Effects of acclimation on the toxicity of stream water contaminated with zinc and cadmium to juvenile cutthroat trout.
abstract: We investigated the influence of acclimation on results of in situ bioassays with cutthroat trout in metal-contaminated streams. Cutthroat trout (Oncorhynchus clarki) were held for 21 days (1) in live containers at a reference or "clean" site having dissolved metals near detection limits (0.01 microg/L cadmium [Cd] and 2.8 microg/L zinc [Zn]; hardness 32 mg/L as CaCO(3)) and (2) at a site in a mining-impacted watershed having moderately increased metals (0.07 microg/L Cd and 38 to 40 microg/L Zn; hardness 50 mg/L as CaCO(3)). The 96-hour survival of each treatment group was then tested in situ at five sites from September 5 to 9, 2002, and each group exhibited a range of metal concentrations (0.44 to 39 microg/L arsenic [As], 0.01 to 2.2 microg/L Cd, and 0.49 to 856 microg/L Zn). Survival was 100% at three sites for both treatments. However, a higher percentage of metal-acclimated fish survived at the site with the second highest concentrations of Cd and Zn (0.90 and 238 microg/L, respectively) compared with fish acclimated at the reference site (100% vs. 55%, respectively). Survival was 65% for acclimated fish and 0% for metal-naïve fish at the site with the largest metal concentrations (2.2 microg/L Cd and 856 microg/L Zn). Water collected from the site with the largest concentrations of dissolved metals (on October 30, 2002) was used in a laboratory serial dilution to determine 96-hour LC(50) values. The 96-hour LC(50) estimates of naïve fish during the in situ and laboratory experiments were similar (0.60 mug Cd/L and 226 microg Zn/L for in situ and 0.64 microg Cd/L and 201 microg Zn/L for laboratory serial dilutions). However, mortality of naïve cutthroat trout tested under laboratory conditions was more rapid in dilutions of 100%, 75%, and 38% site water than in situ experiments.
authors.affiliation: Jackson Field Research Station, Columbia Environmental Research Center, United States Geological Survey, PO Box 1089, Jackson, WY 83001, USA. david_harper@usgs.gov
authors.forename: D D
authors.initials: DD
authors.lastname: Harper
authors.forename: A M
authors.initials: AM
authors.lastname: Farag
authors.forename: W G
authors.initials: WG
authors.lastname: Brumbaugh
mesh_terms: D000064:Acclimatization; D000818:Animals; D001681:Biological Assay; D019187:Cadmium Compounds / Q000032:analysis / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005618:Fresh Water / Q000032:analysis*; D008018:Life Cycle Stages / Q000187:drug effects / Q000502:physiology; D008136:Longevity / Q000187:drug effects; D017683:Oncorhynchus; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D017967:Zinc Compounds / Q000032:analysis / Q000633:toxicity*
chemical_list: D019187:Cadmium Compounds; D014874:Water Pollutants, Chemical; D017967:Zinc Compounds