上海滴水湖两种枝角类牧食对浮游植物群落影响的模拟研究

于2012年9月通过浮游动物添加实验,研究了大型溞(Daphnia magna)和隆腺溞(Daphnia carinata)对上海滴水湖浮游植物群落结构的影响.结果表明,实验组氨氮和可溶性活性磷浓度与空白组相比显著增加,大型溞组浮游植物密度较空白组降低了70.3％,隆腺溞组浮游植物密度较空白组降低了80.0％,叶绿素a浓度分别下降了80.4％和75.2％,叶绿素a与氨氮、可溶性活性磷呈显著相关性.浮游植物的群落结构较空白组也发生较大变化,硅藻、蓝藻和绿藻密度比例明显降低,隐藻、裸藻和甲藻在实验结束时没有检出,说明大型溞和隆线溞能有效控制水体中浮游植物密度,并能够对浮游植物群落结构产生影响.同时,附着藻类密度较空白组也有明显减少,说明大型溞和隆线溞对附着藻类也有一定的牧食作用.

Effects of Two Cladocerans Grazing on the Community of Structure of Phytoplankton in Dishui Lake in Shanghai

The grazing effects of two cladoceran species (Daphnia magna and D. carinata) on the community structure of phytoplankton of Lake Dishui in Shanghai was studied in September 2012. The results showed the concentration of NH+ 4-N, soluble reactive phosphorus (SRP) and chlorophyll-a obviously increased comparing with the control. In the group of D. magna and D. carinata, the concentration of NH+ 4-N increased 2.26-fold and 3.82-fold respectively, the concentration of SRP increased 3.41 times and 3.32 times respectively, the concentration of chlorophyll-a decreased 80.4% and 75.2% respectively. Meantime, the concentrations of NH+ 4-N and SRP showed a significant relationship with chlorophyll-a in the Daphnia treatment. The community structure of phytoplankton significantly changed when the Daphnia were added. The density of phytoplankton decreased 70.3% and 80.0% when D. magna and D. carinata were added respectively. The density of Chlorophyta , Cyanophyta and Bacillaripohyta decreased 69.61%, 64.78% and 31.38% respectively in D. magna treatment. The density of Chlorophyta , Cyanophyta and Bacillaripohyta decreased 96.41%, 62.65% and 66.84% respectively in D. carinata treatment. The Cryptophyta, Euglenophyta and Pyrrophyta were not found at the end of experimentation. The experiments showed D. magna and D. carinata can efficiently control the density and change the community structure of phytoplankton. At the same time the density of periphyton obviously decreased, which showed that D. magna and D. carinata can graze the periphyton.