浮游动物调控对浮游藻类的影响

The effects of zooplankton removal on planktonic algae

浮游动物可以通过牧食作用来抑制浮游藻类的增长,同时浮游动物排泄的营养盐又可以促进浮游藻类的增长,二者的强弱是浮游动物控制浮游藻类的关键。通过人为去除处理组水体中的浮游动物,研究浮游动物生物量和群落结构的不同对富营养水体中浮游藻类的影响。研究结果显示处理组浮游动物总生物量低于空白组,且缺乏大型枝角类溞属(Daphnia sp.);去除浮游动物显著降低了水体中的总氮和总磷浓度以及浮游藻类生物量(叶绿素a),同时增加了附着藻的生物量;并且影响了浮游藻类群落结构:对照组是空星藻(Coelastrum sp.)为优势种而处理组则为湖丝藻(Limnothrix sp.)和四集藻(Palmella sp.)。结果表明浮游动物排泄营养盐产生的上行效应大于牧食作用产生的下行效应。

The growth of planktonic algae can be prohibited by zooplankton grazing. However, the nutrient excretion of the zooplankton enhances the growth of the plantonic algae. The intensity of the two effects is the key factor for zooplankton to coritrol of plantonic algae. In order to investigate the effect of zooplankton biomass and community structure on planktonic algal in eutrophic shallow aquatic system, we conducted an experiment with two treatments： one with zooplankton removal by artificial as treatment group and the other without zooplankton removal as control. The result of zooplankton removal was the total biomass of zooplankton lower and fewer of Daphnia sp. than control. The results showed that zooplankton removal significantly reduced the total nitrogen （TN）, total phosphorus （TP） and planktonic algal biomass （Chl a）; meanwhile it increased the biomass of periphyton. Besides the community structure of planktonic algal was different： the dominant species of control was Coelastrum sp. and the other was Limnothrix sp. and Palmella sp. The present study indicates that bottom-up control by nutrients from zooplankton excretion is greater than top-down control by zooplankton grazing.