The effect of unionized ammonia on the survival and reproductivity of freshwater cladoceran Moina macrocopa

Abstract

Moina macrocopa were exposed to different concentrations of unionized ammonia at pH 7.0±0.43 and temperature of 25.3±0.38 °C in this study. Results show that mortality increased with increasing unionized ammonia concentration. Complete mortality was recorded at 3.6 X 10·1 mg NH3 L- 1 • The 24-hour LC50 and 48-hour LC50 values were 0.077 and 0.070 mg NH3 L- 1 respectively. As for chronic test, four concentrations were experimented; control, environmental concentration (6.92 X 10-4 mg NH3 L- 1 ), nonobserved effective concentration (2.09 X 10·3 mg NH3 L- 1 ) and 48-hour LC 10 (1.18 X 10·2 mg NH3 L- 1 ). Average longevity, lethal time that causes 50% mortality (LT50), net reproductive (Ro) and intrinsic rate of population increase (r) were reduced with the increased concentration of test solutions. Mean generation time (T) at 6.92 X 10-4 mg NH3 L- 1 was higher compared to control treatment and the value gradually decreased with higher concentrations. These results suggest that toxicity of unionized ammonia will cause negative impact to the present population of Moina macrocopa