磷浓度对小环藻、大型溞和金鱼藻三者相互作用的影响

为了解磷浓度对水生植被恢复和生物操纵效果的影响, 分别用小环藻(Cyclotella sp.)、大型溞(Daphnia magna)和金鱼藻(Ceratophyllum demersum)代表浮游植物、浮游动物和大型沉水植物建立水生微宇宙模型, 在25℃、2600 lx光强和11 mg/L氮浓度条件下, 分别研究小环藻与大型溞、小环藻与金鱼藻、小环藻-大型溞-金鱼藻共培养时4种磷浓度(0.05、0.1、0.5和2 mg/L)下小环藻、大型溞、金鱼藻的增长率以及培养液中氮磷去除率的变化。结果表明: 小环藻与大型溞、小环藻与金鱼藻两两共培养时, 磷浓度为0.05-2 mg/L时, 金鱼藻和大型溞均生长良好, 小环藻受到明显抑制, 其密度保持较小幅度的正增长。在小环藻-大型溞-金鱼藻三者共培养时, 在0.05-2 mg/L的磷浓度范围内大型溞和金鱼藻生长良好, 与两两共培养相比, 小环藻则受到了更大程度的抑制, 在磷浓度为0.05-0.1 mg/L时藻密度呈现负增长. 这说明在水生态系统中, 大型浮游动物和沉水植物对浮游藻类的联合控制效果远好于各自单独的控制效果, 该控制效果随磷浓度的提高而减弱, 以0.1 mg/L的磷浓度为最佳。在实验结束后测定氮磷去除率发现, 在最低磷浓度(0.05 mg/L),即磷限制时, 水中磷去除率最高, 在最高磷浓度(2 mg/L), 即氮限制时, 水中氮去除率最高。

EFFECTS OF PHOSPHORUS CONCENTRATION ON INTERACTIONS AMONG CYCLOTELLA SP., DAPHNIA MAGNA AND CERATOPHYLLUM DEMERSUM

In the present study, the effects of phosphorus concentration on bio-manipulation and restoration of aquatic vegetation were determined. Cyclotella sp., Daphnia magna and Ceratophyllum demersum were selected to be respectively as the representative of phytoplankton, zooplankton and submerged macrophyte to construct an aquatic microcosm system. The growth rate of Cyclotella sp., D. magna, and C. demersum and removal rate of nitrogen and phosphorus were tested in the certain conditions 25, 2600 lx illumination, 11 mg/L nitrogen concentration, four phosphorus concentration (0.05, 0.1, 0.5, 2 mg/L) and three types of co-culture operations]. Our results showed that D. magna and C. demersum grew well but Cyclotella sp. was suppressed and its consistency kept slowly positive growth at 0.05-2 mg/L phosphorus concentration in the two co-culture systems (Cyclotella sp. and D. magna co-culture system, Cyclotella sp. and C. demersum co-culture system). In the co-culture system of Cyclotella sp., D. magna and C. demersum, the growth of D. magna and C. demersum was improved, but Cyclotella sp. was suppressed greater at 0.05-2 mg/L phosphorus concentration. Cyclotella sp. showed negative growth at 0.05-0.1 mg/L phosphorus concentration. Our results illustrated that the inhibition effect of zooplankton and large aquatic plants co-culture on the algae was better than that the single zooplankton or large aquatic plants. This inhibition effect decreased with the phosphorus concentration increasing. And the best inhibition effect presented at the phosphorus concentration0.1 mg/L. The highest phosphorus removal presented in the lowest phosphorus treatment (0.05 mg/L), while the highest nitrogen removal presented in the highest concentration of nitrogen (2 mg/L) at the end of the experiment.