The ammonia effects to the habitat requirements and adaptability of Daphnia magna

摘要

In all of the pollutants in the Wenyuhe River Basin, ammonia is the most important one, which changed from 0.2 mg/L to more than 70 mg/L. In order to assess habitat requirements and adaptability to the aquatic environment, the effects of different concentration ammonia (0, 0.02, 2,10, 20 and 70 mg/L) on Daphnia magna were tested. After 48-h, the immobility rate increased to about 60% in the exposure of 70 mg/L, which suggested that the acute toxicity occurred. Therefore, the 21-d effects of ammonia on F0 D. magna and the 10-d effects of ammonia on Fl D. magna were carried out in the treatments of 0, 0.02, 2, 10, and 20 mg/L. The results suggested that the body length, the dry weight, the mean spawning number, and the mean molting frequency of F0 changed from 3.17 ±0.09 mm, 10.90 ± 0.10 mg, 125.50 ±15.60 and 2.35 ±0.11 to 2.85 ±0.13 mm, 4.90 ± 0.60 mg, 88.60 ±30.10, and 3.08 ±0.33 respectively. The intrinsic rate of natural increase (r) decreased with increasing concentrations of ammonia nitrogen especially in those animals exposed to 20 mg/L. The body length, the dry weight, the mean spawning number, and the mean molting frequency of F1 changed from 2.47 ±0.18 mm, 3.09 ± 0.13 mg, 16.50 ±3.60, and 2.13 ±0.10 to 2.64 ±0.04 mm, 2.64 ± 0.33 mg, 0.00 ± 0.00, and 3.22 ± 0.12 respectively. These results showed that higher ammonia concentration affected the habitat requirements of D. magna significantly. Meanwhile, the body length difference between F0 and F1 suggested that continuous exposure to ammonia could improve the adaptability of the offspring.