INTERACTION OF IONIZED AND UN-IONIZED AMMONIA ON SHORT-TERM SURVIVAL AND GROWTH OF PRAWN LARVAE, MACROBRACHIUM...

Area of Science:

• Aquatic toxicology
• Crustacean aquaculture
• Environmental chemistry

Background:

• Ammonia is a common toxicant in aquaculture systems.
• Understanding ammonia's impact on aquatic organisms is crucial for sustainable practices.

Purpose of the Study:

• To investigate the toxicity of ammonia to Macrobrachium larvae across different pH levels.
• To elucidate the mechanisms underlying ammonia toxicity at varying pH.
• To assess the impact of sublethal ammonia concentrations on larval growth.

Main Methods:

• Testing ammonia toxicity to Macrobrachium larvae at three pH levels (6.83, 7.60, 8.34).
• Determining 144-hour LC50 values for ammonia at each pH.
• Evaluating the effects of sublethal ammonia exposure on larval growth.

Main Results:

• LC50 values decreased significantly with increasing pH (80, 44, 14 mg/L at pH 6.83, 7.60, 8.34 respectively).
• Ammonia toxicity is influenced by both NH3 and NH4+ ions, with NH4+ inhibition increasing at lower pH.
• Sublethal ammonia exposure (at pH 6.8 and 7.6) resulted in a 26% reduction in average dry weight compared to controls.

Conclusions:

• Ammonia toxicity mechanisms differ with pH: NH3 diffusion at high pH and NH4+ transport inhibition at low pH.
• Ammonia is unlikely to be a significant threat in properly managed crustacean aquaculture systems.
• Findings are relevant for optimizing water quality management in shrimp farming.