【作者】 邢伟；

【导师】 刘永定；

【作者基本信息】 中国科学院研究生院（水生生物研究所） ， 环境科学， 2007， 博士

【摘要】 随着水体富营养化的加剧,蓝藻水华发生的频率和幅度也日益增加。大规模的蓝藻水华降低了水资源利用效能,引起严重的生态破坏及巨大的经济损失,而蓝藻毒素的产生也给公众健康带来极大的隐患。清楚地认识到这些问题的严重性之后,围绕蓝藻水华的治理工作就陆续展开,但焦点大都集中在水体中的氮、磷等常量营养元素,很少有人研究水体中的微量元素在蓝藻水华形成和消亡过程中所起的作用。本论文按照“以微量营养盐的加富或缺乏作为防止和辅助防止水华的一种手段”的科学设想（hypothesis）,分别从三个不同尺度――滇池试验区6.01 km²,滇池岸边的围隔100 m²,实验室100-500 mL三角烧瓶,研究了微量元素铁对水华蓝藻的生态生理学效应。主要结果如下:1.从2003年3月到2004年2月,在大尺度――滇池6.01 km²试验区,研究了铁元素的分布、形态、浓度、迁移转化及其与蓝藻物种组成变成的关系。结果表明,铁、相关的理化因子和蓝藻物种组成是随季节变化而变化的;颗粒态铁和溶解态铁占总铁的比例相近,均为40⁵0%,而胶体态铁只占总铁的5⁹%;三种不同形态铁之间是可以相互转化的,适应浮游植物及水生植物的不同需要;铁在这种大尺度试验区对蓝藻水华的形成与消亡没有显著影响,蓝藻物种的变化是由多个因子决定的;通过典型相关分析（CCA）得知,铜绿微囊藻（Microcystis aeruginosa）的生物量和优势度主要受硝酸盐氮、亚硝酸盐氮、总磷、溶解氧、和水温的影响,而水华束丝藻（Aphanizomenon flos-aquae）的生物量和优势度主要受氨氮的影响。2.把尺度缩小到滇池岸边的100 m²围隔,从2003年6月到10月,在蓝藻水华暴发期间,继续研究不同形态铁对水华蓝藻的生态生理学影响。结果表明,蓝藻水华优势种M. aeruginosa和惠氏微囊藻（Microcystis wesenbergii）在pH7⁹和水温20 oC左右的条件下生长旺盛,消耗大量的亚铁,使亚铁浓度大幅度下降;溶解氧和磷酸盐对亚铁浓度无显著影响;在水华蓝藻严重发生的条件下,水体中的总铁和其它不同形态铁的浓度无显著意义的变化,而亚铁浓度变化与水华蓝藻的种群密度和叶绿素a的变化呈显著负相关。在淡水富营养型湖泊中,总铁不构成限制性因子,而铁的生物可利用性则是与水华消长直接相关的重要因素。3.继续缩小尺度至室内实验的100⁵00 mL三角烧瓶中,期望能用水华蓝藻的生理学结果解释和阐明水华蓝藻的生态学问题及现象。（1）用不同浓度的[Fe³⁺]处理从滇池分离得到的优势水华蓝藻--M. aerugi- nosa和M. wesenbergii,研究了它们的生长,叶绿素a,PSII的光合活性以及铁限制条件下铁载体（siderophore）产量的变化。结果表明:它们只能在一定范围的[Fe³⁺]内（0.01-100μM）生长;铁限制严重抑制藻类的生长,损害光合器官,降低光合活性;藻类自身能产生抵抗铁缺失、铁限制或铁富足的物质（如siderophore等）。M. aeruginosa与M. wesenbergii相比,在铁限制条件下,其产出的铁载体量多,说明其需要更多的铁盐来满足生理代谢活动的需要,但其对高铁胁迫的耐受性却比M. wesenbergii差。（2）以滇池优势藻株M. wesenbergii为材料,研究铁限制和补铁实验对M. wesenbergii的生长,叶绿素a,酸/碱性磷酸酶,硝酸还原酶及类囊体膜上的H⁺-ATP酶,Mg²⁺-ATP酶和Ca²⁺-ATP酶的影响。结果表明:缺铁造成膜通透性改变,离子浓度严重失衡,酶被激活,活性升高,但长时间的缺乏强烈抑制了生长和叶绿素a的增加;补铁后这些酶的活性都急剧增长,但其生长（OD665）和叶绿素a的升高幅度不显著。（3）以滇池优势藻株M. aeruginosa为材料,研究了不同环境因子（温度、光照、不同氮源）对其生长特性、光合作用和磷吸收的影响。结果表明:在铁限制条件下,温度、光照、氮源对M. aeruginosa的生长无显著影响,光合活性快速降低;而铁富足条件下,30 oC温度,30μmol quanta·m^-2·s^-1光照,硝态氮是其生长最好的环境条件,此条件下藻细胞对磷的吸收速率也较快。更多还原

【Abstract】 Cyanobacterial blooms due to the increasing eutrophication have been a worldwide serious environmental problem in water. Severe cyanobacterial blooms reduced the availability of water resource, causing serious ecological damage and gigantic economic losing, further more, the cyanotoxins biosynthesized from bloom-forming cyanobacteria may pose the major health concerns to humans, as well as to the wildlife. Efforts for cyanobacterial bloom control have been made since people are clearly aware of these serious problems. For eutrophication control, most of the past work has been focused on reducing macronutrients, such as nitrogen, phosphorus, little have been done about the effects of micronutrient on the formation and disappearance of cyanobacterial blooms. According to a hypothesis of that,“regarding the micronutrient enrichment, or deficiency, as a measure or an assistant method in the formation of cyanobacterial blooms”, this paper reported the results from experiments in different scales, they were, 6.01 km² experimental area in Lake Dianchi, 100 m² enclosures near Lake Dianchi and 100-500 mL conical flasks in laboratory. Ecophysiological effects of iron on the bloom-forming cyanobacteria were studied. The main results are as followings:1. Experiments were conducted in the northeastern part of the shallow, hypertrophic lake Dianchi from March 2003 to February 2004. The experimental area was 6.01 km², in a relatively large scale. Iron concentrations were measured for three size fractions: particulate iron （φ>0.22μm）, colloidal iron （φ: 0.025-0.22μm） and soluble iron （φ<0.025μm）, and the main environmental factors were also synchronously analyzed. Results showed that size-fractionated iron, related physico- chemical factors and cyanobacterial species composition all varied with seasonal changes; colloidal iron accounted for only 5⁹%, while particulate iron and soluble iron accounted for 40⁵0% of total iron respectively; size-fractionated iron can transform into each other, thus, it could satisfy the growth requirements of phyto- plankton and aquatic plants. Significant linear correlations were found among the size-fractioned iron, and significant correlations were also obtained between chlorophyll a and environmental factors, such as TN, TP and secchi depth data; but no obvious correlation was found between iron and chlorophyll a in this larger scale experimental area. In addition, cyanobacterial species composition was decided by many factors; results of CCA analysis suggest, the abundance and dominance of M. aeruginosa were influenced by TP, NO₃^--N, NO₂^--N, DO and WT, and the abundance and dominance of A. flos-aquae are influenced by NH₄⁺-N.2. Secondly, experiments were done in 100 m2 enclosures closely nearby lake Dianchi from June to October 2003, scale was much smaller than the above-mentioned experiment area. Results showed that, under the conditions of pH 7⁹ and water temperature 17.5²0.5 oC, photoplankton thrived and absorbed ferrous iron, so the concentrations of ferrous iron decreased highly; DO, phosphate and dissolved total phosphate had no strong influences on the concentrations of different forms of iron; ferrous has significant correlations with population density and chlorophyll a content of phytoplankton. Under serious cyanobacterial bloom, total iron is not a limiting factor in eutrophic freshwater lakes, but iron bioavailability played an important role in waterbloom formation and disappearrance.3. With smaller scale further, experiments were carried out in 100⁵00 mL conical flasks in laboratory under certain conditions. Physiological results in these cases would be helpful to elucidate some ecological phenomena of cyanobacterial bloom formation.（1） After M. aeruginosa and M. wesenbergii, the two dominant species in lake Dianchi, were treated with different iron （III） concentrations, variances of growth rate, chlorophyll a, PSII photochemical efficiency and siderophore production were observed and determined. Results showed that, these algae grew only in a certain range of iron （III） (0.01¹00μM [Fe³⁺]); under iron-limited condition, growths was inhibited, pigments and photosynthetic apparatuses were damaged, so as to caused the yield, ETRmax and Ik all declined sharply. By the way, the algae produced some protective substances under stress conditions, such as siderophore et al., and showed small differences of Iron requirement, as M. aeruginosa required higher iron concentration as compared with M. wesenbergii.（2） Changes in growth rate, chlorophyll a, activities of ACP/ALP, NR, and Mg²⁺, Ca²⁺, H⁺-ATPase on thylakoid membrane of M. wesenbergi were studied under iron limitation and iron addition conditions. Results showed that all these parameters decreased under iron-limited condition and increased markedly after iron enrichments.（3） Complex effects of temperature, light, different nitrogen sources and iron on growth, PSII photochemical efficiency and phosphorus uptake of M. aeruginosa were studied. Results showed that under optimal temperature, light and nitrogen, iron limitation inhibited the growth and decreased the PSII efficiency of M. aeruginosa. Under an iron-replete condition, the optimal growth conditions were temperature 30 oC, light intensity 30μmol quanta·m^-2·s^-1 and nitrate-nitrogen, In this case, the phosphorus uptake rates were highly fast.更多还原