藻华聚集的环境效应:对漂浮植物水葫芦光合作用的影响

Environmental Effects of Algae Bloom Cluster: Impact on the Floating Plant Water Hyacinth Photosynthesis

利用适应性强、生物量大的水生植物来净化污染水体,已成为目前水体生态修复的一种快捷有效的方法.然而,在夏季蓝藻水华严重聚集的水体,藻华聚集后对水生植物的生理生态影响及其环境效应,尚缺乏系统研究.本研究以水葫芦为代表,模拟在高温阶段(水温WT>25℃)、水华严重聚集时,对水葫芦的光合作用的影响进行研究,以揭示蓝藻水华聚集后造成的浅水生态系统中水生植物消亡的深层机制,并为减轻藻华聚集对水生植物的不良影响、充分发挥水生植物的水体净化功能提供理论依据.结果表明,藻华聚集会很快消耗掉水生植物根区内的溶氧,呈现缺氧状态(DO<0.2 mg·L-1);植物根区内ORP出现明显下降现象,实验进行1 d后低于-100 m V,实验结束时达-200 m V,水体呈现强还原环境.与对照相比,根区内p H值低0.7个单位.藻华细胞在死亡、分解后释放大量的无机营养盐于水体中,植物根区内的NH+4-N含量比对照实验中高102倍;较高的NH+4-N含量(平均为45.6 mg·L-1)加之缺氧的协迫作用,导致植物机体受到破坏,植物的光合作用能力严重下降.叶片的平均净光合速率仅为对照的0.6倍,实验结束时其光合速率Pn为3.96μmol·(m2·s)-1,而同期对照实验的叶片净光合速率Pn为22.0μmol·(m2·s)-1;叶片蒸腾速率仅为对照的0.55倍,至实验结束时其蒸腾速率为1.38 mmol·(m2·s)-1,同期对照实验的叶片蒸腾速率为7.61 mmol·(m2·s)-1,表明藻华长期的聚集对植物产生了不可逆的伤害作用.在实际生产中,要避免蓝藻的严重堆积和快速消亡,以减轻藻华暴发对植物的伤害,充分发挥植物的水体净化功能.

It is an efficient and effective ecological restoration method by using the adaptability,large biomass of aquatic plants to purify the polluted water at present. However,there is a lack of systematic research on the impact on the physiological ecology of aquatic plants and its environmental effects of algae blooms cluster in summer. The aim of this paper is to reveal the mechanism of macrophytes demise in a shallow ecosystem by studying the influence on photosynthesis of water hyacinth caused by the cynaobacterial blooms gathered,and also to provide the theoretical basis for full effects of purification function of macrophytes to reduce the negative effects on the aquatic plants after algae blooms gathered during the higher temperature( not lower 25℃) through simulating experiments. Results showed the dissolved oxygen quickly consumed in root zone of aquatic plants after algae blooms gathered and showed a lack of oxygen( DO < 0. 2 mg·L- 1); and the ORP was lower than- 100 m V after 1 d,and it declined to- 200 m V at the end of the experiment,and p H declined 0. 7unit compared with that of control group( CK). There were lots of nutrients releasing to the water after the algae cell died and the NH+4-N concentration was 102 times higher than that of the control group root zone. And the macrophytes photosynthesis reduced quickly and the plant body damaged with the intimidation of higher NH+4-N concentration( average content was 45. 6 mg·L- 1) and hypoxia after algae cell decomposed. The average net photosynthesis rate,leaf transpiration rate were0. 6 times,0. 55 times of the control group,and they reduced to 3. 96 μmol·( m2·s)- 1,1. 38 mmol·( m2·s)- 1,respectively. At the end of the experiment,they were 22. 0 μmol·( m2·s)- 1and 7. 61 mmol·( m2·s)- 1for the control group. Results also showed the algae bloom together had the irreversible damage to the aquatic plants. So in the practice of ecological restoration,it should avoid the harm to the plant after the algae bloom cells gathered and decomposed so as to play the purification function of the plant in the ecological rehabilitation project.