Physiological effects of chronic copper exposure to rainbow trout (Oncorhynchus mykiss) in hard and soft water: evaluation of chronic indicators

• Published in: Environmental toxicology and chemistry 2000-09, Vol.19 (9), p.2298-2308
• Main Authors: Taylor, Lisa N., McGeer, James C., Wood, Chris M., McDonald, D. Gordon
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Copper; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on vertebrates; Fundamental and applied biological sciences. Psychology; Oncorhynchus mykiss; Rainbow trout; Toxicity
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1002/etc.5620190920

Effects of chronic copper exposure on a suite of indicators were examined: acute toxicity, acclimation, growth, sprint performance, whole-body electrolytes, tissue residues, and gill copper binding characteristics. Juvenile rainbow trout were exposed for 30 d to waterborne copper in hand water (hardness = 120 mg/L as CaCO3, pH = 8.0, Cu = 20 and 60 microgram/L) and soft water (hardness = 20 mg/L as CaCO3, pH = 7.2, Cu = 1 and 2 microgram/L). Significant acclimation to the metal occurred only in fish exposed to 60 microgram/L, as seen by an approx. twofold increase in 96-h LC50 (153 vs 91 microgram Cu/L). Chronic copper exposure had little or no effect on survival, growth, or swimming performance in either water hardness, nor was there any initial whole-body electrolyte loss (Na+ and Cl-). The present data suggest that the availability of food (3% wet body weight/day, distributed as three 1% meals) prevented growth inhibition and initial ion losses that usually result from Cu exposure. Elevated metal burdens in the gills and livers of exposed fish were measures of chronic copper exposure but not of effect. Initial gill binding experiments revealed the necessity of using radiolabeled Cu (64Cu) to detect newly accumulated Cu against gill background levels. Using this method, we verified the presence of saturable Cu-binding sites in the gills of juvenile rainbow trout and were able to make estimates of copper-binding affinity (log K(gill) = Cu) and capacity (Bmax). Furthermore, we showed that both chronic exposure to Cu and to low water calcium had important effects on the Cu-binding characteristics of the gills.