Effect of acute and chronic ammonia and nitrite exposure on oxygen consumption and growth of juvenile big bellied seahorse

Juvenile big bellied seahorse Hippocampus abdominalis were exposed acutely and chronically to elevated ammonia and nitrite {24 h exposure: 0·01, 5·0, 10·1, 14·8 and 19·9 mg l−1 total ammonia‐nitrogen [TA‐N] and <0·001, 74·4, 99·2 and 123·6 mg l−1 [NO2‐N] nitrite‐nitrogen and 35 days exposure: 0·11, 0·55, 1·67 and 3·07 mg l−1 TAN and <0·001, 0·92, 4·67 and 9·10 mg NO2‐N l−1}. Significant (P<0·001) increases in oxygen consumption rate and ventilation frequency occurred at 14·8, 19·9 mg l−1 TA‐N and 99·2, 123·6 mg l−1 NO2‐N for acutely exposed fish. Oxygen consumption rate was significantly (P<0·05) elevated at 1·67 and 3·07 mg l−1 TA‐N in chronically treated fish and ventilation frequency increased significantly (P<0·05) at 0·55, 1·67, 3·07 mg l−1 TA‐N and 4·59, 9·10 mg l−1 NO2‐N. There were no significant differences in growth between controls and ammonia exposed fish. Mortalities occurred at 14·8, 19·9 mg l−1 TA‐N.