Acute Toxicity of Ammonia and Nitrite to White Shrimp Penaeus setiferus Postlarvae

Penaeus setiferus postlarvae were exposed to acute levels of ammonia, nitrite, and to a mixture of both by a short‐term static method, The 24h, 48‐h and 72‐h LC50 values for un‐ionized ammonia were 1.49, 1.21 and 1.12 mg/L NH3‐N (un‐ionized ammonia as nitrogen), and 11.55, 9.38 and 8.69 mg/L ammonia‐N (un‐ionized plus ionized ammonia as nitrogen). The 24‐h, 48‐h and 72‐h LC50 values for nitrite were 268.06, 248.84 and 167.33 mg/L nitrite‐N (nitrite as nitrogen). Nitrite was much less toxic than ammonia. The joint effect of ammonia and nitrite on the postlarvae was synergistic at 48‐h exposure and antagonistic after 72 h. Postlarvae of P. setiferus may be considered as organisms sensitive to ammonia and nitrite.