低温下氨氮对淡水浮游藻生长及群落结构影响的生态模拟研究

Simulation of the effect of ammonia nitrogen on the growth and community structure of freshwater phytoplankton under low temperature

为了探讨春季藻类快速生长的机制,研究较低温度下氨氮对淡水浮游藻类生长及群落结构变化的影响,对南开大学新开湖水体藻类进行了室内生态模拟试验研究.在10℃、125μmol·m·s-1光强条件下,培养液中氨氮最终浓度设置为1.0、1.5、2.0、2.5、3.0mg·L-1和对照组(不添加氨氮),每隔1～2天加入氨氮至初始设定值,培养时间为26d.结果表明,浮游藻类在1.0mg·L-1组生长最好,最大生长密度为1.53×105cells·L-1,高于对照组;浮游藻类在高于2.0mg·L-1处理组中生长明显受到抑制,抑制作用随着氨氮浓度的增大而增大,其中3.0mg·L-1处理组的最大生物量仅为5.4×104cells·L-1.随着培养时间的进行硅藻逐渐取代绿藻而成为绝对优势藻,随着藻类的生长,粗刺四刺藻(Treubaria crassispina)在所有处理组中由优势种而逐渐消失,近缘针杆藻(Saffinis affinis)和新月藻(Closterium lunula)在培养后期逐渐成为优势种,但在不同氨氮浓度下表现出不同生长密度.除1.0mg·L-1处理组外,其它处理组中的物种多样性指数差异不显著(p>0.05).氨氮影响浮游藻类的生长,影响优势种的变化,并且对浮游藻类的群落结构变化有一定的影响.

In order to understand the mechanism of rapid growth of algae in spring and the effects of ammonia nitrogen on the growth and community structure of freshwater phytoplankton under low temperature, a laboratory ecological simulation experiment of phytoplankton from Xinkai Lake of Nankai University was conducted. The final concentrations of ammonia nitrogen were set to 1.0, 1.5, 2.0, 2.5, 3.0 mg-L t as well as the control group without addition of ammonia nitrogen, and NH3-N was added in conical flask each 1 or 2 days to keep the initial concentrations for 26 days under the condition of 10 ℃ and 125 μmol·m·s-1. The result indicated that planktonic algae had the best growth in the 1.0 mg·L - 1 group, with the maximum growth density of 1.53 × 105 cells·L-1 and higher than the control group. The growth rate of algae was significantly inhibited in groups with concentration higher than 2.0 mg·L-1 , and the inhibition for algae increased with the increase of ammonia concentration. The maximum density of algae in 3.0mg·L-1 was only 5.4 × 104 cells. L - 1. As incubation proceeded, diatoms gradually replaced the green algae and became absolute dominant species. With the growth of algae, Treubaria crassispina gradually disappeared in all treated groups, Saffinis affinis and Closterium lunula became the dominant species in the late culture stage, but they showed different densities in different concentrations of ammonia nitrogen. Except for 1.0mg·L -1 group, the species diversity index of other treated groups showed no significant difference （p 〉0.05）. Ammonia nitrogen affected the growth of phytoplankon and changed the dominant species, and also influenced the phytoplankton community structure.