【作者】 李春雷；

【导师】 唐学玺；

【作者基本信息】 中国海洋大学 ， 生态学， 2009， 博士

【摘要】 大气CO₂的浓度以前所未有的速度稳步增加是全球性的重大环境问题之一。CO₂等温室气体的增加导致全球气温的上升即“温室效应”的加剧,随之而来的是海平面的上升、生物多样性的丧失和沙漠化的加剧等等,这已影响到整个地面生态系统的变化。全球CO₂浓度升高对生态系统中的绿色植物将产生直接的影响,进而使生物从生态系统、群落、种群、个体、细胞以及分子各个层次水平上发生变化。在整个海洋食物网中,海洋微藻是CO₂加富最直接的响应者,它不仅驱动着整个海洋生态系统的能流和物流,直接和间接地养育着几亿吨的海洋动物,而且对调节全球变化起着重要的作用。本文采用实验生态学的方法从种间、种群、生理生化和分子水平研究了6种海洋微藻:小球藻（Chlorella.sp）、亚心形扁藻（Platymanas subcordiformis）、金藻8701（Isochrysisgalbana Parke 8701）、中肋骨条藻（ Skeletonema costatum ）、盐藻（Dunaliella salina）和赤潮异弯藻（Heterosigma akashiwo）对大气CO₂浓度升高的响应。研究结果如下:1.海洋微藻种群增长对CO₂加富的响应6种海洋微藻的种群增长对CO₂加富都作出了一定的响应,即CO₂加富（5000μl/L）能够显著促进6种海洋微藻:小球藻、盐藻、金藻8701、中肋骨条藻、亚心形扁藻和赤潮异弯藻的种群增长。使其种群增长进入静止期的时间缩短,种群达到的最大细胞密度显著提高（p < 0.05）。6种海洋微藻的种群增长对CO₂加富（5000μl/L）响应的敏感性存在一定的差异,按敏感性由低到高的顺序依次为:小球藻<盐藻<金藻8701<中肋骨条藻<亚心形扁藻<赤潮异弯藻,赤潮异弯藻对CO₂加富最敏感,而小球藻对CO₂加富最不感。2.双藻共培养条件下海洋微藻种群竞争对CO₂加富的响应以赤潮异弯藻和中肋骨条藻为目标微藻,在共培养条件下研究了二者的竞争作用及其对CO₂加富的响应变化。结果发现:起始接种密度对赤潮异弯藻和中肋骨条藻的种群增长有明显的影响。即随着接种密度的提高,2种赤潮微藻种群增长进入指数生长期的时间都相应地提前,进入静止期的时间同样都相应地提前,而种群增长所达到的最大细胞密度均相应地降低。共培养条件下,中肋骨条藻在与赤潮异弯藻的竞争中始终占优势,且随着中肋骨条藻相对起始接种密度的提高,其种群竞争生长的优势越加明显,对赤潮异弯藻种群生长的抑制作用愈加显著。CO₂加富处理可改变赤潮异弯藻和中肋骨条藻种群竞争的关系,使赤潮异弯藻种群竞争能力降低,中肋骨条藻种群竞争能力大大提高。3.多藻共培养条件下海洋微藻种群竞争对CO₂加富的响应选用3种海洋微藻--亚心形扁藻、中肋骨条藻和金藻8701为实验藻种,研究了多藻共培养条件下微藻竞争性平衡以及对CO₂加富的响应变化。结果表明:在正常条件（通空气）下,金藻8701的种群增长动态表现为弱竞争型,中肋骨条藻的种群增长动态为强竞争型,亚心形扁藻种群增长动态为增长型。因此,在多藻共培养体系中,种群竞争向有利于中肋骨条藻种群增长的方向发展,使中肋骨条藻最终成为优势种,而亚心形扁藻则成为亚优势种,金藻8701成为劣势种。CO₂加富（通含5000μl/L CO₂的空气）处理改变了3种海洋微藻的种群增长动态,同时引起了种群竞争平衡的变化。CO₂加富条件下,中肋骨条藻的种群增长动态表现为为增长型,而亚心形扁藻种群增长动态表现为强竞争型,而金藻8701种群增长动态仍然表现为弱竞争型。因此,在多藻共培养体系中,种群竞争向有利于亚心形扁藻种群增长的方向发展,使亚心形扁藻由正常条件下的亚优势变化为CO₂加富条件下的优势种,而中肋骨条藻则由正常条件下的优势种变化为CO₂加富条件下的亚优势种。4.海洋微藻大分子物质合成动态对CO₂加富的响应选用3种海洋微藻--中肋骨条藻、赤潮异弯藻和小球藻探讨CO₂浓度升高对海洋微藻大分子物质合成动态的影响。结果表明:3种海洋微藻DNA合成动态对CO₂加富显示出类似的响应,表现在DNA合成速度加快,DNA合成量增加。3种海洋微藻相比,赤潮异弯藻的DNA的合成对CO₂加富最敏感,其次是中肋骨条藻,而小球藻的DNA的合成对CO₂加富最不敏感。3种海洋微藻RNA合成动态对CO₂加富同样显示出类似的响应,表现在RNA合成速度加快,RNA合成量增加。3种海洋微藻相比,中肋骨条藻的RNA的合成对CO₂加富最敏感,其次是赤潮异弯藻,而小球藻RNA的合成对CO₂加富最不敏感。3种海洋微藻蛋白质合成动态对CO₂加富显示出不同的响应,赤潮异弯藻蛋白质合成对CO₂加富最敏感,表现在蛋白质合成速度加快,蛋白质合成量显著增加。中肋骨条藻蛋白质的合成对CO₂加富相对不敏感,而小球藻蛋白质的合成对CO₂加富没有显示出响应性变化。5.海洋微藻对CO₂加富的生理生化响应选用中肋骨条藻、赤潮异弯藻和小球藻为实验藻种,从生理生化层次继续研究其对CO₂加富的响应变化,结果发现:3种海洋微藻的光合速率、光合固碳速率和碳酸酐酶活对CO₂加富都作出了明显的响应变化,与对照组相比差异显著（p< 0.05）。说明CO₂加富处理刺激了3种海洋微藻的碳酸酐酶活性,从而提高了它们的光合速率和光合固碳速率,这将对其生长产生间接的促进作用。三种海洋微藻相比,赤潮异弯藻的响应最明显,其次是中肋骨条藻,小球藻的响应相对最不明显。3种海洋微藻的硝酸还原酶活性和对N、P的吸收速率对CO₂加富都作出了明显的响应变化,与对照组相比差异极显著（p<0.01）。指示CO₂加富处理刺激了3种海洋微藻的硝酸还原酶活性,从而提高了它们对N、P的吸收速率,这将对其生长产生间接的促进作用。三种海洋微藻对P吸收速率的响应敏感性顺序是赤潮异弯藻>中肋骨条藻>小球藻,对N吸收速率的敏感性顺序是中肋骨条藻>赤潮异弯藻>小球藻,而硝酸还原酶活性对CO₂加富响应敏感性顺序是赤潮异弯藻>小球藻>中肋骨条藻。3种海洋微藻叶绿素a含量对CO₂加富处理都没有作出明显的响应（p> 0.05）。在CO₂加富条件下,其叶绿素a含量与对照组相比无显著差异（p> 0.05）。更多还原

【Abstract】 The steady enrichment of CO₂ at unprecedented speed is one of the seriously global environment problems. The enrichment of greenhouse gas, such as CO₂, has led to an increase in global temperature, and consequent sea level rising, biodiversity loss and desertification aggravation. All these things described above have obviously influenced terrestrial ecosystem. CO₂ enrichment will directly affect green plants in ecosystem, and then caused changes in different levels of organization including ecosystem, community, population, individual, cell and molecule. In the entire marine food web, marine microalgae are the most direct responders to CO₂ enrichment. They not only drive the energy flow and matter cycle in marine ecosystem, fostering million tons of marine animals, but also play an important role in regulating global changes. In present study, experimental ecology studies were conducted on responses of six species of marine microalgae （Chlorella sp., Platymanas subcordiformis, Isochrysisgalbana Parke 8701, Skeletonema costatum, Dunaliella salina, Heterosigma akashiwo） to CO₂ enrichment with respect to interspecies, population, biochemical, physiological, molecule levels. Results showed that:1. Response of population growth of marine microalgae to CO₂ enrichmentAll the six species of microalgae represent responses to CO₂ enrichment. CO₂ enrichment （5000μl/L） could significantly promote population growth of marine microalgae （Chlorella sp., P. subcordiformis, I. galbana, S. costatum, D. salina and H. akashiwo）, and shorten the time of entering the stationary phase. And maximum population densities increased remarkably （p < 0.05）.Differences in sensitivity of microalgal population growth to CO₂ enrichment （5000μl/L） were observed among different microalgae, and the sensitivity was Chlorella sp. < D. salina < I. galbana < S. costatum < P. subcordiformis < H. akashiwo. H. akashiwo was the most sensitive, while Chlorella sp. was the most insensitive.2. Response of interspecies competition to CO₂ enrichment between microalgae in co-culture systemsCo-cultured H. akashiwo and S. costatum were researched to investigate the effect of CO₂ enrichment on interspecies between these. Results showed that the initiative inoculum density had significant effects on population growth of H. akashiwo and S. costatum. And time advances of entering exponential growth phase and stationary phase were observed with increasing in inoculum density for both microalgae. Correspondingly, the maximum population density decreased obviously.In co-culture system, S. costatum was always in predominance in the competition. And the dominance was promoted by increasing inoculum density. CO₂ enrichment could change the relationship of competition between H. akashiwo and S. costatum, and resulted in a reduction of competitive ability of H. akashiwo, while remarkably promoted the competition dominance of S. costatum.3. The responses of population competition to CO₂ enrichment in co-culture systemsCo-cultured P. subcordiformis, S. costatum and I. galbana were researched to investigate competitive balance among these and the effect of CO₂ enrichment on it. Results showed that under normal condition （air inflation）, I. galbana was weak in competition and S. costatum was strong in competition, while P. subcordiformi showed a constant increase in population density. Therefore, in co-culture system, S. costatum took an advantage in competition, and finally became the dominant species. While P. subcordiformi became subdominant species and I. galbana were taken at a disadvantage.CO₂ enrichment treatment （5000μl/L CO₂ inflation） influenced the population dynamics of these three microalgae, and simultaneously influenced the competitive balance. Under CO₂ enrichment conditions, S. costatum showed a constant increase in population density and P. subcordiformi was strong in competition, while I. galbana was weak in competition. Therefore, in co-culture system, P. subcordiformi took an advantage in competition, and finally became the dominant species. While S. costatum became subdominant species and I. galbana were taken at a disadvantage.4. The response of macromolecular substance synthesis in marine microalgae to CO₂ enrichmentCo-cultured P. subcordiformis, Heterosigma akashiwo and Chlorella sp. were researched to investigate the effect of CO₂ enrichment on macromolecular substance synthesis. Results showed that the DNA synthesis represented the response to CO₂ enrichment representing as increase in synthesis speed and content of DNA. For these three microalgae, DNA synthesis in H. akashiwo was the most sensitive to CO₂ enrichment, and it more sensitive in P. subcordiformis than that in Chlorella sp.RNA synthesis represented a similar response to CO₂ enrichment. Protein synthesis in P. subcordiformis was the most sensitive to CO₂ enrichment representing as increase in synthesis speed and content of RNA. And RNA synthesis in H. akashiwo was more sensitive than that in Chlorella sp.Protein synthesis in microalgae showed different response to CO₂ enrichment. Protein synthesis in H. akashiwo was the most sensitive to CO₂ enrichment representing as increase in synthesis speed and content of protein. And protein synthesis in S. costatum was less sensitive to CO₂ enrichment, while that in Chlorella sp. had no obvious response.5. The biochemical and physiological responses of microalgae to CO₂ enrichmentCo-cultured S. costatum, H. akashiwo and Chlorella sp. were researched to investigate the effect of CO₂ enrichment on responses of physiological and biochemical activity. Results showed that photosynthetic rate, carbon fixation and carbonic anhydrase activity represented obvious response to CO₂ enrichment, compared with control groups （p < 0.05）. CO₂ enrichment stimulated an increase in the activity of carbonic anhydrase, so increased the photosynthetic carbon fixation and photosynthetic efficiency and therefore indirectly promoted the increase of microalgae. The response of H. akashiwo was the most sensitive to CO₂ enrichment, and S. costatum was more sensitive than Chlorella sp.Nitrate reductase activity and absorption rate of N, P in microalgae represented obvious response to CO₂ enrichment, and were significantly different compared to control （p< 0.01）. CO₂ enrichment stimulated an increase in the activity of nitrate reductase, so increased the N, P-absorption rate and therefore indirectly promoted the increase of microalgae. The sensitivity of P absorption rate was: H. akashiwo > S. costatum > Chlorella sp. And the sensitivity of N absorption rate was: S. costatum > Chlorella sp. > H. akashiwo. The sensitivity of nitrate reductase was: H. akashiwo > Chlorella sp. > S. costatum.Chlorophyll a contents in microalgae did not represent significant response to CO₂ enrichment （p > 0.05）. Under CO₂ enrichment conditions, the content of chlorophyll showed no obvious difference compared with control groups （p > 0.05）.更多还原