Toxicity of Un-ionized Ammonia and High pH to Post-larval and Juvenile Freshwater Shrimp Macrobrachium rosenbergii |
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Authors: | David L Straus H Randall Robinette John M Heinen |
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Institution: | Department of Wildlife and Fisheries, Mississippi State University, Mississippi State, Mississippi 39762 USA |
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Abstract: | Post-larval and juvenile Macrobrachium rosenbergii were exposed for 72 h at 29 C to four pH levels (8.5, 9.0, 9.5, 10.0) and four concentrations of un-ionized ammonia-nitrogen (0, 1, 2, and 3 mg/L NHj-N). Results indicated potentiation between NH3 and high pH. Juveniles were more tolerant of high pH and NH3 than post-larvae. For post-larvae, estimates of 72 h LC50 for pH were 9.43, 9.21, and 8.71 at 0, 1, and 2 mg/L NH3-N, respectively; 72 h LC50 estimates for NH3-N were 2.18 and 1.45 mg/L at pH levels of 8.5 and 9.0, respectively. For juveniles, estimates of 72 h LC50 for pH were 9.91, 9.56, 9.04, and 8.76 at 0, 1, 2, and 3 mg/L NH3-N, respectively; 72 h LC50 estimates for NH3-N were 2.02 and 0.54 mg/L at pH 9.0 and 9.5, respectively. In pond culture of M. rosenbergii , high pH levels can cause mortality at stocking. The 72 h data can be used as an indication of safe stocking levels of pH and ammonia. These data suggest that post-larvae should not be exposed to pH > 9.0 nor to NH3-N > 1 mg/L in the pH range 8.5–9.0 and juveniles should not be exposed to pH > 9.5 nor to NH3-N > 0 mg/L at pH 9.5, > 1 mg/L at pH 9.0, or > 2 mg/L at pH 8.5. |
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