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Estuaries in NSW

Estuarine Water Quality

Ammonia

Ammonia is a highly soluble gas which is present in water as ammonium ions (NH₄⁺) and as free ammonia (NH₃).

High concentrations of ammonia are acutely toxic to fishes, and may cause loss of equilibrium, hyper-excitability, increased rates of breathing, cardiac output and oxygen uptake, and in extreme cases, convulsions, coma and death. At lower concentrations, ammonia has many ill-effects on fishes, including a reduction in hatching success, reductions in growth rate and morphological development, and pathologic changes in gill, liver and kidney tissue.

Acute ammonia toxicity is modified by several factors which include DO concentration, temperature, pH, previous acclimation to ammonia, fluctuating or intermittent exposure, carbon dioxide concentration, salinity and the presence of other toxicants. The acute and chronic toxicity of ammonia has been shown to increase as pH increases. Data on temperature effects on acute ammonia toxicity are limited and somewhat variable, but indicate that ammonia toxicity to fish increases as temperatures fall.

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