苦草光合作用日变化对水质的影响

通过静态模拟试验研究晴天时苦草(Vallisneria asiatica)的光合作用日变化对水质的影响. 分别采用水下饱和脉冲荧光仪(Diving-PAM)和多参数水质监测仪(YSI)在线监测苦草叶绿素荧光参数与水质，并定时采样测定水中营养盐的浓度. 结果表明，苦草叶片光合作用的相对电子传递速率(rETR)日变化与叶片表面的光合有效辐射(PAR)和温度同步，呈单峰曲线；光系统Ⅱ(PSⅡ)实际量子产量(Y)的日变化呈“W”型；水体的pH和ρ(DO)的日变化与苦草光合作用趋势一致，也呈单峰曲线，而电导率和浊度与光合作用没有相关性；水体中ρ(TN)一直保持稳定，ρ(TP)在23:00时出现峰值.苦草的光合作用能引起水体pH，ρ(DO)和ρ(TP)的改变；且pH和ρ(DO)对底泥磷释放的影响可能是一个动态平衡的过程. 

Effects of Diel Variation of Vallisneria asiatica Photosynthesis on Water Quality

Influence on water quality of diel variationof Vallisneria asiatica photosynthesis on a sunny day was investigated in a static simulative experiment. The chlorophyll fluorescence parameters of Vallisneria asiatica and water quality were monitored in situ by Diving-PAM and YSI, respectively. Hourly nutrient concentrations were also measured during the 24 hour experiment. The results showed the diel variation of relative electron transport rate (rETR) of leaf photosynthesis changed synchronously with the photosynthetic active radiation (PAR) on the leaves and temperature as a single-peak curve. The actual quanta output of PSⅡin the light showed as “W”. Water pH and dissolved oxygen (DO) mass concentration also presented a single-peak curve affected by photosynthesis.Neither electrical conductance nor turbidity changed linearly with the photosynthesis. Total nitrogen (TN) mass concentration remained stable during the 24 hourexperiment, while total phosphorus (TP) mass concentration reached a peak valueat 23:00. The results indicated that photosynthesis was a key factor controlling water pH, DO and phosphorus mass concentration. It also indicated that the diel variations of pH and DO mass concentrations caused by macrophyte photosynthesis may cause dynamic balance of phosphorus release from sediments.