pH与氨的交互作用对壶状臂尾轮虫(Brachionus urceolaris)种群增长、繁殖及存活的影响

Combined effect of pH and un-ionized ammonia on population growth,reproduction and survival rates of the rotifer Brachionus urceolaris

观测了pH7—10之间（间隔1）与非离子氨氮（NH3-N）浓度分别为0．5、1、2、5mgNH3-N／L和10mg NH3-N／L水质条件下壶状臂尾轮虫（Brachionus urceolaris）种群的增长、繁殖和存活率。结果表明，在没有NH3-N存在的情况下，轮虫在pH7—10之间都能存活，pH7时种群的净增殖率、内禀增长率都最高，pH8时世代时间最长。在适宜的pH条件下（pH7、8），NH3-N浓度小于2mg／L时，轮虫的存活曲线变化不大，繁殖率几乎不受影响；在NH3-N浓度达到5mg／L时，存活时间缩短，繁殖率明显下降；当NH3-N浓度达到10mg／L时，壶状臂尾轮虫在48～72h内死亡，且不产生幼体。在非适宜pH条件下加入NH3-N后，种群的内禀增长率变为负值，净增殖率明显下降，种群出现负增长。以上结果表明高pH与NH3-N的交互作用对轮虫种群的增长与存活具有严重的负影响。

The population growth, reproduction and survival rates of a rotifer （Brachionus urceolaris ） population were studied in growth media over a range of pH-values （pH 7 -10） and different concentrations of un-ionized ammonia （NH3- N ：0.5,1,2,5 and 10mg/L）. The results that in the absence of un-ionized ammonia, the rotifers could survive across the entire pH range（ pH 7 -10）. Both the population net reproductive rate and the intrinsic growth rate were highest at pH 7, but the generation time was longest at pH 8. While at a favorable range of pH （ pH 7,8 ） and at a concentration of NH3-N below 2mg/L, the age-specific survivorship curve and population growth rates similar to the control. At a concentration of 5mg NH3-N/L, the age-specific survivorship decreased and the population growth rate a lot declined. Under the 10mg NH3- N/L concentration, the individuals died in 48 -72h, carrying no egg. When exposed to un-ionized ammonia at an unfavorable pH, the population＇s intrinsic growth rate was negative, its reproductive output dropped and the population declined. The above results indicate that a combination of high pH and high concentration of un-ionized ammonia has a clear negative effect on growth and survival of the rotifer, B. urceolaris.