以沉水植物金鱼藻(Ceratophyllum demersum)为研究对象,研究了较高营养条件(N：10-30 mg/L, P：1-3 mg/L)对金鱼藻去除氮、磷能力的影响,金鱼藻的含磷量、生物量与净光合作用速率对营养负荷的响应。结果表明,金鱼藻-沉积物处理系统可有效去除氮、磷(去除率80%以上),但去除效率随水中营养盐浓度的升高而下降。试验结束时各试验组金鱼藻总磷含量达7.01-13.09 mg/g (平均9.03 mg/g),显著高于对照组(2.85-3.17 mg/g,平均3.05 mg/g),表明金鱼藻可以吸收水体中的磷。营养盐对金鱼藻生长有明显抑制,其抑制作用随营养盐浓度增高而加剧,除对照组外,各试验组金鱼藻均有叶片脱落,试验结束时金鱼藻生物量降至初始生物量的48.3%-63.3%。在较高营养水体中,金鱼藻的净光合作用速率由试验开始时-0.037-0.058 mg/(g·h)显著上升至试验结束时0.18-0.44 mg/(g·h),而对照组变化不大,这表明在试验后期,随着水体营养盐浓度降低,金鱼藻开始进行恢复性生长,说明水体营养盐浓度对金鱼藻的净光合作用速率和生长速率有明显影响。金鱼藻尚不适宜作为滇池草海生态修复的先锋物种。%Ceratophyllum demersum is a free-floating submerged angiosperm and is an important indicator of clearwater state. C. demersum can absorb nutrients from the water column and is usually used as a pioneer macrophyte in the re-storation of eutrophic lakes. The main objectives of this study were to evaluate (1) the purification ability of C. demer-sum to remove phosphorus and nitrogen at high levels of nutrient concentrations (N:10-30 mg/L,P:1-3 mg/L);(2) the ecophysiological response of C. demersum (e.g. net phosphorus uptake by plants, biomass changes and net photo-synthetic rate) under high nutrient concentrations;and (3) the potential of C. demersum used as a pioneer and construc-tive species for macrophyte recovery in hyper-eutrophic Lake Caohai (China). C. demersum samples were collected from a pond near Lake Dianchi and were pre-cultured in the experimental aquaria for 30 days before experiments. The plants were transplanted and grown in four 20 cm × 20 cm × 60 cm aquaria with the following conditions:12 cm depth of sediment and 18 L of tap water (control) and the other three with increased nitrogen and phosphorus concentrations (Level 1, N:10 mg/L, P:1 mg/L;Level 2, N:20 mg/L, P:2 mg/L;and Level 3, N:30 m/L, P:3 mg/L). The changes of nutrient concentrations, biomass of plant and periphytic algae, chlorophyll-a content of phytoplanktonic algae, net pho-tosynthetic rate of plant, phosphorus uptake and water content of plant were evaluated during culture period (n = 30 days). We observed that C. demersum and sediment system efficiently removed phosphorus and nitrogen from water column (removal rate > 80%); however, the addition of nitrogen and phosphorus decreased the efficiency. Phosphorus contents of C. demersum were significantly higher in the three treatment groups (7.01-13.09 mg/g, ave. 9.03 mg/g) compared to those in the control group (2.8-3.17 mg/g, ave. 3.05 mg/g). In addition, we found that plant growth was obviously inhibited by high nutrient levels. Except the control, plant biomass loss, (abscission of leaves) among the treatment groups decreased 48.3%-63.3%at the end of the experiment. We also observed that net photosynthetic rates of the plants in the treatment groups significantly increased from baseline [-0.037-0.058 mg/(g·h)] to the end [0.18-0.44 mg/(g·h)]; however, the change in the control group was not significant. Results indicated that some reco-very of the macrophyte may be due to the decrease of nutrient concentration at the end of culture period. We concluded that nutrient concentration significantly influenced the growth and net photosynthetic rate of C. demersum and this plant is not suitable for being used as a pioneer macrophyte in the current restoration of Lake Caohai.
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