【作者】 于娟；

【导师】 唐学玺；

【作者基本信息】 中国海洋大学 ， 生态学， 2004， 博士

【摘要】 大气CO₂水平在21世纪将倍增。随着工业化的发展，除了CO₂，氯氟代烃（CFCs），CH₄和N₂O也将增多，这些气体的增多将使臭氧层减薄，使到达地球表面的UV-B辐射呈增强趋势，CO₂和UV-B将随着未来全球气候的变化而同时增加。UV-B辐射对藻类有明显的伤害作用，其损伤的主要目标是蛋白质、DNA和光合色素等，CO₂浓度升高对海洋微藻的生物量、光合作用有促进作用，而UV-B辐射与CO₂加富共同作用对海洋微藻的研究还未见报道。本文以几种海洋微藻为实验对象，通过研究其对UV-B辐射增强与CO₂加富单独以及复合响应，探讨UV-B辐射增强与CO₂加富对海洋微藻的生理生态学、细胞学的影响机制，以期为全球气候变化对水生生态系统的影响提供科学依据。通过实验，我们得到以下结果： 1．UV-B辐射对海洋微藻的生长具有抑制作用，并且随着辐射剂量的不断增大而抑制作用增强。在单养的情况下，短期内（48h）8种藻对UV-B的敏感性顺序为骨条藻＜塔胞藻＜盐藻＜小球藻＜角毛藻＜亚心形扁藻＜小新月菱形藻＜金藻8701。 高浓度CO₂（5000μl／L）能够促进海洋微藻的生长，且随时间的延长，增长幅度越大。高浓度CO₂（5000μl／L）对6种藻生长影响的敏感性依次为：小球藻＜盐藻＜金藻8701＜小新月菱形藻＜亚心形扁藻＜塔胞藻。 2．研究了在三种UV-B辐射剂量（0，2.88 J／m²和5.76 J／m²）对三种藻混养的竞争性平衡的影响。本实验的两个UV-B辐射剂量（2.88 J／m²和5.76 J／m²）使三种藻的总生物量都大幅降低，竞争平衡也发生了变化。实验表明，UV-B对三种藻的敏感性顺序为金藻＞小新月菱形藻＞亚心形扁藻；增强的UV-B使对UV-B具有高耐受力的亚心形扁藻提供了竞争优势，使种间竞争平衡向着有利于亚心形扁藻的方向发展。海洋微藻对Uv-B辐射增强与CO:加富共同作用的复合响应 与低浓度COZ相比，高浓度COZ促进三种藻的生长，并且混养与单养相比较，高浓度CO:对三种藻的敏感性发生了变化，通气培养到第21天时，高浓度CO:的优势种、亚优势种、劣势种并未发生变化。 增强UV一B+高COZ与对照（空气）相比，三种藻的细胞密度显著降低。所以，尽管COZ浓度升高能够促进藻的生长，但并不能抵消UV一B辐射对海洋微藻生物量的影响，而且增强UV一B十高CO:与对照（空气）相比，种间竞争和优势种发生了很大变化。 3.采用透射电镜对微藻的超微结构进行研究射增强（未通气）使盐藻叶绿体结构受到破坏。研究发现，UV一B辐线粒体内晴局部溶解，穿入到蛋白核内的类囊体发生缺失或断裂，累积许多小的淀粉粒和脂肪小球，液泡异常增大，数量增加，内含物减少，高尔基体则变为排列松弛的储泡，醋泡的外围顶端并没有特别膨大，表明Uv一B辐射增强对盐藻细胞结构的变化是盐藻适应外界环境UV一B辐射的一种反应。 UV一B辐射增强（通空气）使盐藻细胞的线粒体数目增多，但个别线粒体的内靖溶解，类囊体溶解，叶绿体被膜部分皱缩，高尔基体有一个排列松弛的滞泡，储泡的外围顶端并没有特别膨大，核膜部分溶解。 经uv一B辐射剂量为8.8)/mZ处理后的小球藻（未通气），类囊体片层缺失、溶解，类囊体中的含有光合色素的小体被漂白;线粒体内蜡部分溶解;有的小球藻开始出现轻微的质壁分离现象;经UV一B辐射剂量为13.SJ/mZ处理后的小球藻（未通气），类囊体排列错乱、崩解，出现质壁分离的现象，有的细胞壁开始脱落，线粒体严重变形，内峭大部分溶解;细胞内基质电子密度比较高;细胞内出现大量空白区，叶绿体中的含有光合色素的小体被漂白且可见几个含有光合色素的小体的空壁。由此可见，随着UV一B辐射剂量的增大，小球藻的细胞结构被破坏的程度越大。 盐藻细胞在低浓度C02（360 p l/L）培养下细胞内有一个发育良好的、由淀粉盘包围的蛋白核，而在高浓度CO:（5000 p I/L）培养的细胞内没有发现蛋白核或蛋白核不明显，高尔基体排列紧密，类囊体排列整齐，片层清晰，线粒体内晴清晰。 增强UV一B+高CO:处理的细胞内形成许多小块的淀粉粒，有的细胞海洋微藻对UV-B辐射增强与CO:加富共同作用的复合响应核膜已经溶解，类囊体部分溶解;在质膜和叶绿体膜之间有许多线粒体，但线粒体的内峭己经溶解。蛋白核外围的淀粉鞘断裂成几个不连续的大小不一的淀粉粒。高尔基体排列松弛。结果表明，CO:加富并不能完全抵消UV一B辐射对盐藻细胞结构的破坏。 4.UV一B辐射对两种海洋微藻的生理生化的研究表明:（1） UV一B辐射能抑制微藻的生长并且抑制微藻光合作用;相对较低剂量的UV一B辐射刺激小球藻的光合色素（叶绿素a（Chl一a）和类胡萝卜素（Car）），较高的Uv一B辐射剂量抑制chl一a和Ca:含量;（2）非变性聚丙烯酞胺凝胶电泳方法对蛋白质组成分析的结果表明，较低剂量的UV一B辐射处理可以升高可溶性蛋白质的含量，随着UV一B辐射剂量的加大，蛋白质含量明显降低;（3）UV一B辐射使活性氧（过氧化氢（HZOZ）和超氧阴离子自由基（02’一））含量升高，且UV一B辐射时间延长，升高幅度增大;另外，小球藻和亚心形扁藻之间存在差异，且随着UV一B辐射时间延长，藻种间的差异更趋明显:（4）随着Uv一B辐射时间更多还原

【Abstract】 Atmospheric levels of CO2 are expected to double during the 21st century. In addition to CO2, chlorofluorocarbons (CFCs), CH4 and N2O are also increasing with industrialization. The increase of these trace gases is expected to deplete the stratospheric ozone column with a subsequent increase in the amount of solar UV-B radiation reaching the earth. Both CO2 and UV-B radiation are expected to increase simultaneously with future changes in global climate. UV-B radiation can significantly damage microalgae. The main targets are protein, DNA and photosynthetic pigments, and so on. Elevated CO2 concentration can promote the biomass, photosynthesis of microalgae, while combined effects of UV-B radiation and enriched CO2 on marine microalgae have not been reported. In this article, we take several species of marine microalgae as experimental objectives, and discuss the mechanisms of enhanced UV-B radiation and enriched CO2 on the physiological ecology and cytology of marine microalgae by studying enhanced UV-B radiation, elevated CO2 singlely and CO2 /UV-B radiation in combination, to supply experimental base for aquatic ecosystem with changes in global climate. Through experiments, we get results as follows:1. UV-B radiation inhibited the growth of marine microalgae, and the inhibiting action increased as increasing UV-B radiation dosage. Under the condition of solitary cultivation, the sensitivity of short-term (2d) UV-B radiation on solitary cultivated eight species of microalgae was Skeletonema costatum Greville < Platymanas sp. < Dunaliella salina < Chlorella.sp< Chaetoceros miielleri Lemmermann < Platymonas subcordiformis < Nitzschia clostertium< Isochrysis galbama Park 8701.Elevated CO2 can promote the growth of marine microalgae, and as the time was prolonged, the increase amplitude was greater. The sensitivity of six species of algae to elevated €62 was Chlorella. s p < Dunaliella salina< Isochrysis galbama Park 8701 < Nitzschia clostertium< Platymonas subcordiformis< Platymanas sp.2. The effects of three UV-B radiation doses (0, 2.88 J/m2, 5.76 J/m2) on competitivebalance of three species of algae under the condition of mixed cultivation were examined. The total biomass of three species of microalgae under the UV-B dosage of 2.88 J/m2, 5.76 J/m2 was greatly reduced, and the competitive balance changed also. The experiment showed that, the sensitivity of UV-B radiation on three species of microalgae was Isochrysis galbama Park 8701>Nitzschia clostertium >Platymonas subcordiformis. So enhanced UV-B radiation provide competitive dominance for Platymonas subcordiformis, which has high tolerance to UV-B, and in general, the effect of UV-B was in favor of Platymonas subcordiformis. On the 21st day, in the treated groups of UV-B radiation (2.88 J/m2, 5.76 J/m2), Platymonas subcordiformis became the dominant algae.Compared with low concentration COi, elevated COi promoted the growth of three algae, and elevated COa changed the sensitivity of three species of algae under the condition of mixed cultivation, comparing to under the condition of solitary cultivation. On the 21st day of the experiment, the dominant algae, subdominant algae and rogue algae were not changed.Compared with control (air), enhanced UV-B + elevated CO2 greatly decreased cell densities of three species of algae. Therefore, although elevated CO2 can promote the growth of algae, it can not counteract the effect of UV-B radiation on biomass of marine microalgae. Compared with control (air), enhanced UV-B + elevated COa changed the interspecific comptition and dominant algae.3. Effects of enhanced UV-B radiation (not bubbling) on the ultrastructure of Dunaliella salina were examined. After exposure to enhanced UV-B radiation, dramatic ultrastructual changes occurred in the chloroplast of D. salina; some cristae of mitochondria were disintegrated; the thylakoid penetrating into the pyrenoid was lost or broken. After exposure to enhanced UV-B radiation, enhanced UV-B radiation caused the accumulation of starch grains and lipid globu更多还原