ANZECC/ARMCANZ (2000) guideline value of 910 lg total NH3/L.The corresponding PC90 value for chronic effects in a disturbed environment was 750 lg total NH3–N/L. For acute effects, as might occur over a short time frame, a PC95 value of 1.55 mg total NH3–N/L was calculated (based on acute NOECs calculated by dividing the acute LC50 data by 5). The corresponding acute PC90 value was 2.26 mg total NH3–N/L.