金鱼藻(Ceratophyllum demersum)调控浮游植物捕获磷与生长的策略

水体浮游植物具有捕获利用磷的能力以及沉水植物能够显著抑制水体中藻类生长已得到国内外广泛共识,但相应的潜在机制尚缺乏深入了解.本研究选取金鱼藻(Ceratophyllum demersum)为研究对象,基于室内模拟实验,探讨了沉水植物调控浮游植物捕获磷与过度生长的机制.结果显示,尽管未种植金鱼藻的对照组上覆水中总磷、总溶解态磷和可溶性活性磷的平均浓度均显著高于种植金鱼藻的实验组(约4倍),但是两个系统中这3种磷浓度随时间的变化趋势均符合S形的对数曲线.实验组藻类密度、有效光量子产量、总碱性磷酸酶活性(TAPA)以及细颗粒碱性磷酸酶活性(细颗粒APA)也远低于对照组.此外,对照组中粗颗粒碱性磷酸酶活性(粗颗粒APA)占TAPA的44.7%,显著高于细颗粒APA.结构方程模型结果表明,对照组水体藻类密度对TAPA具有直接的正向作用,而金鱼藻的生长显著弱化了不同形态磷与APA、藻类密度、细菌动力以及光量子产量之间的相互作用.这说明沉水植物对水体浮游植物生长的调控具有多种策略.

Strategies of Ceratophyllum demersum to govern algal phosphorus-acquisition and algal proliferation

Phosphorus acquisition by algae and the algal growth inhibition governed by submerged macrophytes have been long-term observed, but the general underlying mechanism is not clear. Here, we assembled mesocosms and subjected them to two treatment regimes, one planted with Ceratophyllum demersum and the other unplanted control, to address the causal mechanisms. The results showed that the average concentration of total phosphorus, total dissolved phosphorus and soluble reactive phosphorus in the unplanted control were significantly higher (about 4 folds) than those in system with macrophyte control, but all their observed values changed with time following S-shaped Logistic curves. Additionally, significantly higher values of algal density, quantum yield, total alkaline phosphatase (APA) and bacterial APA were also detected in the control. And the algal alkaline phosphatase, as the predominant component accounted for up to 44.7% of the total APA, was significantly higher than that of bacterial APA. Structural equation modeling indicated that significant positive influence on total APA only occurred in the unplanted control, and C. demersum growth had a significant decoupling effect on the relationship between different forms of phosphorus and APA, algal density, bacteria dynamic and quantum yield. These results suggested that submerged macrophytes have different tactics to govern algal proliferation.