Responses of oxygen consumption, ammonia-N excretion and urea-N excretion of Penaeus chinensis exposed to ambient ammonia at different salinity and pH levels

Abstract

Oxygen consumption (O-2 mg g(-1) h(-1)) of Penaeus chinensis juveniles (0.76 +/- 0.05 g) increased with increased concentration of ambient ammonia-N in the range of 0-10 mg 1(-1), but decreased with increased salinity level in the range of 10-30 p.s.u. (practical salinity units) and pH level in the range of 7.0-8.5. Urea-N excretion and nitrite-N excretion of shrimp increased with increased salinity, pH and ambient ammonia-N levels. Whereas, ammonia-N excretion of shrimp decreased with increased salinity, pH and ambient ammonia-N levels. Ammonia-N uptake occurred when shrimp were exposed to ambient ammonia-N at 5 mg 1(-1) or greater at every salinity and pH level tested. Shrimp at an increased salinity level, and at an increased concentration of ambient ammonia-N enhanced their urea-N excretion, an effect that was more pronounced at high pH than at low pH.