【作者】 李娜；

【导师】 高大文；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 硕士

【摘要】 水华暴发是一个多因素综合作用的结果,如温度、光照、氮磷营养盐、微量元素、CO₂等。其中CO₂作为藻类光合作用的底物,对藻类生长和水华暴发影响重大。大量化石燃料的燃烧及森林绿地面积的锐减,在增加大气中CO₂来源的同时减少了CO₂的吸收源,导致大气中CO₂浓度剧增,有人预计到21世纪末,CO₂浓度将倍增。大气CO₂浓度的增加对藻类光合作用及水华暴发的影响令人关注。本试验以普遍存在于我国各地水体中的水华优势种铜绿微囊藻为材料,设置了7个CO₂浓度,研究CO₂浓度变化对铜绿微囊藻生长及光合活性的影响。试验结果显示,随着CO₂浓度增加,铜绿微囊藻的生物量及叶绿素a浓度呈现出先升高后降低的趋势。CO₂浓度在400～6400μL/L范围内,藻的生长得到促进,浓度继续升高则会对生长产生抑制作用,铜绿微囊藻生长的最适CO₂浓度在800μL/L左右。不同浓度CO₂条件下生长的铜绿微囊藻叶绿素荧光活性和光合放氧速率都存在显著性差异（P<0.05）。高浓度（25600μL/L）CO₂环境为光合作用提供了充足的碳源,藻类碳浓缩机制CCMs下调,固碳所需能量减少,饱和光强降低。铜绿微囊藻受极高浓度CO₂胁迫,叶绿素合成受阻,光能的吸收、传递,尤其是转化受限,影响藻细胞内的电子传递过程,最大电子传递速率ETRmax降低。此外,高浓度CO₂条件下,铜绿微囊藻的暗呼吸速率增强,维持细胞基本生理活动所需能量增加,光合作用合成的能量仅有很少一部分用于细胞生长繁殖和叶绿素合成,能量不足可能是铜绿微囊藻光合色素合成受阻及生长被抑制的原因之一。透射电镜扫描结果显示,高浓度CO₂条件下生长的铜绿微囊藻与对照组（400μL/L）相比,外部结构没有显著变化,但细胞内类囊体数目减少,且出现不规则排列,与正常细胞差异显著,表明藻细胞的光合机构受到损伤。CO₂浓度的适当增加会促进藻类生长,浓度过高反而会产生抑制作用。高浓度CO₂对铜绿微囊藻的抑制作用主要是由于细胞光合机构受损,叶绿素合成受阻所致。更多还原

【Abstract】 Water bloom, which occurred frequently and strongly, has been seriously affected people’s life and its occurring mechanism & treatment methods were paid more attention by scholars in the world. Water bloom is a combined result of multiple factors such as temperature, light, nutrients, trace element, carbon dioxide, etc. As a substrate, carbon dioxide （CO₂） plays an important role in algae’s photosynthesis. Atmospheric CO₂ has risen dramatically as a result of human activities such as fossil fuel burning and deforestation, it was estimated that the concentration of CO₂ in atmosphere will be doubled at the end of 21st century. Effects of elevated CO₂ on algae’s photosynthesis were worth to be concerned.Seven different CO₂ concentrations were set in this experiment to study the effects of CO₂ on Microcystis aeruginosa’s growth and physiological activity. Results showed that biomass and chlorophyll a content of Microcystis aeruginosa increased firstly and then decreased with the increase of atmospheric CO₂. Algal growth was promoted at the range of 400～6400μL/L CO₂ concentration, the optimum CO₂ concentration for growth of Microcystis aeruginosa was about 800μL/L. Under different CO₂ concentration, Microcystis aerugonisa’s biomass, chlorophyll fluorescence and oxygen evolution rate were significantly different （P<0.05）. High CO₂ provided sufficient carbon soure for algal photosynthesis, the carbon-concentrating mechanism （CCMs） weak down and energy required reduced so that the saturated light intensity decreased. By stress of high ,synthesis of chlorophyll a was blocked and limited light absorption, transmission & transformation especially, which would influence the electron-transfer process, leading to the lower of the maximum electron transport rate ETRmax. In addition, under high CO₂ condition, Microcytis aeruginosa’s dark respiration rate increased, then energy needed to maintain algal physiological activity increased and there was little erergy used for cell growth and reproduction. Lack of energy maybe the main reseason for block of the biosynthesis of chlorophyll a. Compared with the control , Microcystis aeruginosa, which was under high CO₂ （25600μL/L） condition, its external structure has not changed, but inner structure of cell were significantly different from the control cells, the number of thylakoid reduced and arranged irregularly. It indicated that algal photosynthetic apparatus has been damaged.Appropriate increase of atmospheric CO₂ will promote algae growth, in contrast, excessively high CO₂ will cause inhibition. Effects of high CO₂ inhibited the growth of Microcystis aeruginosa mainly due to the damage of photosynthetic apparatus and block of chlorophyll a synthesis. The optimal CO₂ concentration （800μL/L） to the growth of Microcystis aeruginosa would be helpful to understanding the occurring mechanism of Microcystis aeruginosa bloom.更多还原