No abstract

Pcnaeus monodon juveniles (35.4 ± 2.2 mm TL) were exposed to seawater (20 ppt) having different concentrations of total ammonia (NH3+ NH,+) and nitrite. Median lethal concentration (LC50) was determined with static‐renewal tests. The LC50, of total ammonia‐N, NH3‐N and niMte‐N on shrimps decreased with increase of exposure time. The 24, 48, 72, % and 120 h LC50 were 94.96, 61.09, 47.47 45.58 and 38.00 mg/L total ammonia‐N (2.68, 1.73, 135, 1.29 and 1.08 mg/L NH3‐N) and 215.85, 185.33, 88.54, 54.76 and 37.97 mg/L nitrite‐N, respectively. The 144h LC50 of total ammonia‐N and NH3‐N was 36.71 mg/L and 1.04 mgL. The “threshold” of ammonia and nitrite was found at 144h and 120h respectively, from the toxicity curve approaching asymptote. A “safe value” was 3.7 mg/L total ammonia‐N, 0.1 mg/L NH3‐N (20 ppt, pH 7.70, 27C) and 3.8 mg/L nitrite‐N for P. monodon juvenile.