Effect of pH and ammonia on survival and growth of the early larval stages of Penaeus monodon Fabricius

Abstract

Lethal toxicity tests of ammonia at different pH levels (7, 7.5, 8, and 8.5) and its effect on survival and growth of the early larval stages of Penaeus monodon were determined. An increase in ammonia toxicity when the water pH increased was revealed in 96 h toxicity tests. Estimated LT50 decreased from 101.09 to 25.16 h for protozoea exposed to 8 ppm ammonia, from 115.79 to 11.26 h for mysis exposed to 24 ppm, and from 51.41 to 22.58 h for PL exposed to 52 ppm ammonia with increase in pH levels. The effect of 3 and 6 ppm ammonia levels at pH levels of 7.0, 7.5, 8.0 and 8.5 on the survival and growth of P. monodon larvae and postlarvae was also investigated in a 16-day sublethal toxicity test. Results indicated that ammonia at 3 and 6 ppm affects both survival and growth of shrimp. Survival was decreased by 27% in 3 ppm and by 48% in 6 ppm ammonia, while growth was reduced by 4.4% in 3 ppm and by 6.5% in 6 ppm ammonia. Increasing pH of the rearing water resulted in significantly lower survival in protozoea, mysis, and postlarval stages. No interactive effect of pH and ammonia was detected.