Low Levels of Environmental Ammonia Increase Susceptibility to Disease in Chinook Salmon Smolts

Ammonia criteria are established using data from standardized toxicity tests involving healthy animals. Both intrinsic and extrinsic environmental changes affect the immune system, but few toxicity studies consider the overall impact on this system and potential changes in resistance to infection. T...

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Bibliographic Details
Published in:Physiological and biochemical zoology 2006-07, Vol.79 (4), p.695-707
Main Authors: Ackerman, Paige A., Wicks, Beverly J., Iwama, George K., Randall, David J.
Format: Article
Language:English
Subjects:
Ammonia
Ammonia - toxicity
Animals
Blood Glucose
Blood plasma
Disease susceptibility
Dose-Response Relationship, Drug
Fish Diseases - chemically induced
Fish Diseases - etiology
Freshwater fishes
HSP70 Heat-Shock Proteins - blood
Hydrocortisone - blood
Leukocytes
Lymphocytes
Marine
Mortality
Muramidase - blood
Neutrophils
Oncorhynchus tshawytscha
Pathogens
Respiratory Burst
Risk Factors
Salmon
Saltwater
Time Factors
Vibrio anguillarum
Vibrio Infections - chemically induced
Vibrio Infections - veterinary
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Summary:Ammonia criteria are established using data from standardized toxicity tests involving healthy animals. Both intrinsic and extrinsic environmental changes affect the immune system, but few toxicity studies consider the overall impact on this system and potential changes in resistance to infection. To investigate the effects of subacute levels of ammonia in coastal waters on physiological and immunological systems of fish, juvenile Chinook salmon were maintained in seawater (10°C, pH 7.8) and exposed to two concentrations of ammonia, 2.5 and 10 mg/L total nitrogen. Both test levels resulted in increased internal levels of ammonia in the fish. Neither treatment level affected feeding rates. Over a time course of 10 d, numerous significant effects were observed. White blood cell counts changed significantly, as did respiratory burst activity, plasma lysozyme activity, and plasma glucose concentration in both treatments compared to controls. In an experimental infection withVibrio anguillarum, fish previously exposed to subacute levels of ammonia were more susceptible to pathogenic challenge. The findings of this study indicate that a more thorough investigation into the effects of environmental ammonia on fish populations in coastal waters should be undertaken and the current environmental standards reassessed.
ISSN:1522-2152
1537-5293
DOI:10.1086/504615