滇池控藻围隔中水生植物和浮游藻类对不同形态铁浓度的影响

Effects of Aquatic Plant and Phytoplankton on Concentrations of Size-fractionated Iron in Algal Controlling Enclosures

运用围隔试验来研究围隔生态系统内浮游藻类的组成和数量以及水生植物变化对不同形态铁浓度的影响,再反过来探讨微量元素铁在蓝藻水华暴发过程中对水生植物和浮游藻类生态生理的作用,从而为探索治理蓝藻水华的新途径提供基础证据。从2003年6月至10月,定期采样测定了控藻围隔水体中的亚铁、颗粒态铁(>0.22μm)、小胶体态铁(0.22～0.025μm)、溶解态铁(<0.025μm)的浓度和叶绿素a的浓度,同时对浮游藻类进行了组成鉴定和细胞计数。结果表明,不同形态的铁之间是可以相互转化的,胶体态铁比颗粒态铁活跃,是溶解态铁的一个储备库;亚铁与黄藻门细胞数存在显著正相关(r=0.858P=0.0004,N=20),其他形态的铁都与叶绿素a存在显著正相关(r=0.630,P=0.003,N=20);亚铁是浮游藻类和水生植物可以直接吸收利用的形态。围隔系统内浮游藻类的变化还不足以显著地改变铁的浓度,试验围隔内铁浓度的变化主要是因为水生植物的大量消耗。

Iron is essential for aquatic plant and algal growth and plays an important role in their physiology and ecology. In this experiment, enclosures were used to study effects of algae and aquatic plant on the dynamic changes of size-fractionated iron concentrations in four enclosures. In turn, we may discuss the ecophysiological function of iron during the formation and disappearance of cyanobacterial bloom, and also provide some evidences for exploring the treatment of cyanobacterial blooms through this study. The experiments were conducted near the shore of Lake Dianchi. From June to October 2003, water samples were collected periodically from the four enclosures to measure concentra- tions of ferrous iron, particulate iron （〉0.22 pLm）, small colloidal iron （0.22 μm-0.025 μm）, soluble iron （〈0.025μm） and chlorophyll a. The composition of algae was also identified and the number of phytoplankton was counted in the four enclosures. The results showed that particulate iron, small colloidal iron and soluble iron could transform each other. Significant correlations were obtained between ferrous concentration and the number of algae in Xanthophyta （r=0.858, P=0.000 4, N=20）, and significant correlations were also found between different iron forms and chlorophyll a except for ferrous （r=0.630, P=0.003, N=20）. Ferrous iron was a direct uptake form by aquatic plant and algae. Changes of algal composition and number had no marked effect on the concentrations of different iron forms.