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题名: 两种水华蓝藻对磷的生理生化响应及竞争的研究
作者: 沈宏
答辩日期: 2007-06-18
导师: 宋立荣
授予单位: 中国科学院水生生物研究所
授予地点: 水生生物研究所
学位: 博士
关键词: 蓝藻水华 ; 磷 ; 微囊藻 ; 束丝藻 ; 生理生化响应 ; 磷吸收动力学 ; 竞争
其他题名: Studies on Physiological and Biochemical Responses to and Competition for Phosphorus in Two Bloom-forming Cyanobacteria
摘要: 微囊藻(Microcystis)和束丝藻(Aphanizomenon)是富营养水体中最常见的水华蓝藻。蓝藻水华的频繁暴发引起水生态系统结构和功能的损害并对人类健康存在潜在威胁。因此,深入认识蓝藻水华的生消机制一直以来都是科学界研究的热点。磷被认为是浮游植物生长的限制性营养元素,水体中磷的增加是引起富营养化的主要原因之一。本论文研究了两种水华蓝藻微囊藻和束丝藻对磷的生理生化响应以及对磷营养的竞争,试图揭示不同水华蓝藻对磷响应的差异,探讨磷对两种蓝藻水华成因及其竞争关系的影响。具体研究内容和结果如下: (1)在正磷酸盐充足或限制条件下,研究了不同形态的含磷物质-焦磷酸钠、三聚磷酸钠、β-甘油磷酸钠对铜绿微囊藻生长、碱性磷酸酶活性以及培养基中磷浓度的变化的影响。结果表明:在正磷酸盐充足条件下添加三种不同形态的含磷物质,对微囊藻的生长和碱性磷酸酶活性均无明显的影响,微囊藻主要以正磷酸盐作为其生长的磷源。在正磷酸盐限制条件下,添加三种不同形态的含磷物质均能明显促进微囊藻的生长,三种不同形态的含磷物质均能被微囊藻吸收利用,但利用方式不同。其中,微囊藻对β-甘油磷酸钠的吸收最快。焦磷酸钠和三聚磷酸钠的添加对微囊藻碱性磷酸酶活性无显著影响,而β-甘油磷酸钠能显著提高碱性磷酸酶活性。 (2)比较了单细胞和群体微囊藻对磷的生理生化响应。两种表型的微囊藻在磷充足条件下的生理生化特征较相似,对较低磷浓度的响应则不同。长时间的无磷培养对单细胞微囊藻的细胞造成损伤,而群体微囊藻比单细胞耐受缺磷培养的时间长。在较低的磷浓度0.2 mg/L时,单细胞微囊藻的生长、光合放氧活性、Fv/Fm、ETRmax等受到明显的抑制,碱性磷酸酶活性(APA)、胞外微囊藻毒素含量显著升高;而群体微囊藻生理生化特征无明显变化,其APA和胞外毒素含量明显低于单细胞微囊藻,而其抗氧化系酶活性(SOD、CAT)以及光合放氧活性均高于单细胞微囊藻。两种表型的微囊藻在磷吸收和积蓄方面也存在差异。单细胞微囊藻的Km值和Vmax值高于群体微囊藻,群体微囊藻对较低浓度的磷的亲和力较高,单细胞微囊藻保持其生长比群体微囊藻需要更多的磷。两种表型的微囊藻对磷响应的差异主要是由两种微囊藻形态上的差异造成的,群体微囊藻胞外的黏液在其中起了重要的作用。 (3)以BG11为基础培养基,研究了不同浓度的磷对水华束丝藻生长的影响及其磷吸收动力学。结果表明,过高和过低的磷浓度均影响水华束丝藻的生长,20-100 μM是水华束丝藻生长的最适无机磷浓度范围;无机磷浓度低于10 μM,其生长受到明显抑制。水华束丝藻的磷吸收速率与胞外磷浓度关系符合Michaelis-Menten模型,磷吸收半饱和常数和最大磷吸收速率分别为21.031±6.266 μM和1.5093±0.263×10-5 µM P • cell-1 • h-1。 (4)在磷限制连续培养条件下,研究了不同稀释率和不同搅拌速率对铜绿微囊藻和水华束丝藻生长和生理特征的影响以及其磷吸收的特征。结果表明,过高和过低的稀释率均不适合微囊藻的生长,其生长的最适稀释率范围是0.0036-0.0128 h-1;而束丝藻的比生长速率与稀释率呈正比,随着稀释率的升高而升高。微囊藻在静止的条件下比生长速率最大,其比生长速率随着搅拌速率的升高逐渐降低;搅拌速率对束丝藻的生长速率无明显影响。束丝藻的APA在各条件下均高于微囊藻。两种水华蓝藻的磷吸收速率以及比生长速率与磷浓度之间的关系可分别用Michaelis-Menten模型和Monod模型描述,微囊藻的Km和Ks值均低于束丝藻,这表明在低Pi的条件下,微囊藻对磷的竞争较束丝藻更具优势。 (5)研究了铜绿微囊藻和水华束丝藻在磷限制恒化器中的竞争规律,探讨了不同水温和磷对两种蓝藻生长和竞争的影响。结果表明,在25 ºC磷限制的连续培养中,当稀释率较低时(< 0.00736 h-1),微囊藻的生长占优势;当稀释率升高(0.01472 h-1),束丝藻能与微囊藻共存。温度能改变微囊藻和束丝藻的竞争。在较高的温度下(> 19 ºC),微囊藻的生长占优势;在较低的温度下(< 19 ºC),束丝藻的生长占优势。束丝藻的APA高于微囊藻,当在培养基中添加有机磷化合物后,能加速束丝藻的生长,使其在竞争中占优势。实验结果表明,微囊藻和束丝藻优势种群的演替是营养盐与温度协同作用的结果。生物反应器竞争实验的研究结果能部分解释水体中微囊藻和束丝藻优势度的变化和季节演替的发生原因。
英文摘要: Microcystis and Aphanizomenon are among the most dominant bloom-forming species of cyanobacteria in eutrophic waterbodies. The mechanism of their formation and disappearance in freshwater bodies has been always the focus of research due to their harmful effect on aquatic ecosystems and their potential hazard to human health. Phosphorus (P) is always considered the principal nutrient that influences phytoplankton growth in most freshwater bodies, and the oversupply of this nutrient from human sources underlies the eutrophication of water columns. In this thesis, the physiological and biochemical response to P and their competition for P were explored by means of batch culture and continuous culture. The difference in responses of Microcysti and Aphanizomenon to P was discovered. And competitive behaviors of two strains in P-limited continuous cultures condition and field condition were discussed. The main results are as followings: (1) The effects of three phosphoric chemicals in different forms (pyrophosphate sodium, polyphosphate sodium and β-glycerophosphate disodium) on the growth and alkaline phosphatase activity (APA) of Microcystis aeruginosa, and total soluble phosphorus in medium were tested at orthophosphate-repleted and orthophosphate-limited conditions. The results showed that the addition of the three different phosphoric chemicals had no significant effects on the growth rate and APA activity under orthophosphate repleted condition, indicating that orthophosphate (K2HPO4) was the major phosphorus source by M. aeruginosa for its growth. Under orthophosphate-limited condition, however, the addition of the three different phosphoric chemicals promoted the growth rate of M. aeruginosa significantly. The phosphorus in different forms could be utilized effectively by M. aeruginosa but by different utilization ways. β-glycerophosphate disodium was uptaken fast than that of pyrophosphate sodium and polyphosphate sodium by M. aeruginosa. It was demonstrated that APA was increased upon the addition of β-glycerophosphate disodium, but not for pyrophosphate sodium and polyphosphate sodium. (2) The physiological and biochemical response to P in unicellular and colonial Microcystis were compared. The two phenotype strains exhibit physiological differences mainly in terms of their response to low P concentrations. Unicellular strains were damaged when exposed to P-free medium for a long time; whereas colonial strains were endure P-free culture longer. The growth rate, the oxygen evolution rate, Fv/Fm, and ETRmax of unicellular Microcystis strains were significantly inhibited and APA, content of extracellular microcystin were significantly increased at a P concentration of 0.2 mg/L; however, that of the large colonial Microcystis strains were not significant changed. There was also exist difference in P uptake and storage between two phenotype strains. The results of phosphate uptake experiments conducted using P-starved cells indicated that the unicellular strains exhibited higher Km and Vmax values than those exhibited by the colonial strains, which indicates that the latter had a higher affinity for low levels of P. The unicellular strains consumed more P than the colonial strains. The reason for the difference in growth patterns and physiological traits under P-limited conditions may be attributed to the difference in the extracellular structure between the two phenotype strains. The better performance of the colonial strains at low Pi concentrations might be due to the role of mucilage in nutrient sequestration and processing. (3) The effects of P on the growth of Aphanizomenon flos-aquae and uptake of P kinetics were studied using BG11 as basal medium in the laboratory. The results indicated that either lack or excessiveness of P concentration would inhibit growth of A. flos-aquae. The optimal P concentrations for growth of A. flos-aquae would be 20-100 μM; and the growth were significantly inhibited when P concentration less than 10 μM. The relationship between P uptake rate of A. flos-aquae and the external phosphate concentrations can fit by Michaelis-Menten model. The half saturation constant for P uptake and maximal uptake rate was 21.031±6.266 μM and 1.5093±0.263×10-5 µM P • cell-1 • h-1, respectively. (4) The effects of dilution rates and agitation rates on the growth and physiological character of M. aeruginosa and A. flos-aquae were studied using unialgal chemostat cultures with various supply rates of culture medium where P limited algal growth. In unialgal continuous cultures, either lack or excessiveness of dilution rates was disadvantage for the growth of M. aeruginosa. The adaptable dilution rates for its growth would be 0.0036-0.0128 h-1. The growth rates of M. aeruginosa reached maximum under stable condition and decreased with the increasing of agitation rates. Comparatively, the growth rates of A. flos-aquae were correlated with dilution rate and increased with the increasing of dilution rate. There were no significant differences between growth rates of A. flos-aquae and agitation rates. The relationship between the P uptake rates and specific growth rate of two strains and extracellular P concentration in the culture vessel can fitted to Michaelis-Menten model and Monod model, respectively. The M. aeruginosa exhibited lower Km and Ks values than those exhibited by the A. flos-aquae, which implied that the former had a more competitive advantage for Pi. (5) In order to figure out the effects of different environmental factors on competition between the cyanobacteria M. aeruginosa and A. flos-aquae. The competitive interaction between two strains was studied using mixed chemostat cultures under various dilution rates and various temperatures. In P limited mixed culture at 25 ºC, M. aeruginosa was dominate at dilution rates less than 0.00736 h-1; M. aeruginosa and A. flos-aquae can coexist in mixed culture at a higher dilution rate of 0.01472 h-1. Temperature can affect their competitive interactions. M. aeruginosa dominated at higher temperature (> 19 ºC), whereas A. flos-aquae out-competed at lower temperature (< 19 ºC). The APA was greater in the A. flos-aquae than in the M. aeruginosa. Addition of organic P can accelerate the growth of A. flos-aquae, which made it out-competed. These results revealed that the succession of M. aeruginosa and A. flos-aquae was the outcome of synergistic actions of nutrients and temperature. The result from chemostat cultures explains in part the occurrence of seasonal succession of Microcystis and Aphanizomenon in Dianchi Lake.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ihb.ac.cn/handle/342005/12158
Appears in Collections:中科院水生所知识产出(2009年前)_学位论文

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Recommended Citation:
两种水华蓝藻对磷的生理生化响应及竞争的研究.沈宏[d].中国科学院水生生物研究所,2007.20-25
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