磷浓度对铜绿微囊藻、大型溞和金鱼藻三者相互作用的影响

Influences of phosphorus concentration on interactions among Microcystis aeruginosa,Daphnia magna and Ceratophyllum demersum

为了解磷浓度对生物操纵和水生植被恢复效果的影响,以铜绿微囊藻、大型溞和金鱼藻分别作为浮游植物、浮游动物和大型沉水植物的代表,在25℃、2000—3000lx光强和11mg/L氮浓度条件下,研究两者和三者共培养时4种磷浓度(0.2、0.5、1.0、1.5 mg/L)下各自的增长率和培养液中氮磷去除率的变化。结果表明:两者共培养时,磷浓度不大于0.2mg/L时,有利于大型溞的繁殖和金鱼藻的生长;磷浓度介于0.5—1.5mg/L时,铜绿微囊藻呈正增长趋势,而金鱼藻的生长则明显受抑制。三者共培养时,所有磷浓度下的大型溞数量及金鱼藻生物量均不同程度的升高,且铜绿微囊藻的生长得到了有效抑制,以磷浓度为0.2—0.5mg/L时效果最佳;N/P比值对藻、溞、草间的相互作用有重要影响,在藻-溞系统中,大型沉水植物的加入可以大大提高抑藻效果,减小N/P比值波动带来的不利影响。磷浓度为0.5mg/L时的水体氮磷去除效果好于其他磷浓度梯度。

In this study, Microcystis aeruginosa, Daphnia magna and Ceratophyllum demersum were selected to be respectively as the representative of phytoplankton, zooplankton and submerged macrophyte to evaluate the influence of phosphorus concentration on biomanipulation and aquatic vegetation restoration. When two or three of them were cultured together, with 4 kinds of phosphorus concentration（0.2,0.5,1.0,1.5 mg/L）, 25℃, 2000-3000lx illumination and 11mg/L nitrogen concentration, the changes of growth rate and rate of removing nitrogen and phosphorus were studied. The results indicated that it was advantageous to D. magna multiplication and C. demersum growth when two of the three organisms were cultured together and the phosphorus concentration was no more than 0.2 mg/L in pairwise culture. M. aeruginosa was keeping multiplication fast, but C. demersum biomass decreased obviously when phosphorus concentration range was 0.5 to 1.5mg/L. When all organisms were cultured together, both D. magna density and C. demersum quantity increased, but M. aeruginosa density declined markedly, and the effect was best when phosphorus concentration range was 0.2 to 0.5mg/L. The ratio of N/P could obviously influence their interactions of M. aeruginosa, D. magna and C. demersum. In the co-culture system of M. aeruginosa and D. magna, addition of submerged macrophyte could enhance the effect of algal control, and lowered the negative effect that was triggered by the wave of N/P ratio. When phosphorus concentration was 0.5mg/L, there was better elimination effect on the nitrogen and phosphorus than other phosphorus concentration gradient.