【作者】 蔡恒江；

【导师】 唐学玺；

【作者基本信息】 中国海洋大学 ， 生态学， 2007， 博士

【摘要】 赤潮是全球性的海洋生态灾害，具有全球性、多发性、复杂性和高危害性等特点，已经成为亟待解决的重大海洋环境问题之一。我国是赤潮灾害多发国，近年来，由于人类活动引起的近岸水体富营养化程度加剧，导致赤潮频发，对近岸水域的生态环境和沿岸水产业的可持续发展造成极大的威胁。建立切实可行的赤潮防控方法势在必行。利用存在于海洋环境中的天然生物因子，如大型海藻等进行赤潮的生物学调控已经越来越引起人们的重视。已有的研究表明，大型海藻能通过营养竞争或是克生作用来抑制赤潮微藻的生长。另一方面，臭氧层衰减而导致的UV-B（280nm~320nm）辐射增强是另一个全球性的环境问题之一，不仅能够对海洋生物体构成伤害，而且还会对海洋生态系统产生明显的影响。本文以青岛沿岸常见的大型海藻—孔石莼(Ulva pertusaKjellm)和赤潮微藻—赤潮异弯藻(Heterosigma akashiwo ( hada)hada)为材料，在实验生态条件下，把石莼和赤潮异弯藻分别分为单养（对照）、UV-B辐射处理的单养、混养和UV-B辐射处理的混养四个试验组，研究了石莼-赤潮异弯藻相互作用及其对UV-B辐射的响应。结果发现：一、石莼-赤潮异弯藻相互作用的研究（1）研究了不同起始营养盐条件和初始生物量对石莼-赤潮异弯藻种间竞争的影响，结果表明：石莼和赤潮异弯藻发生相互竞争作用时，利用性竞争和干扰性竞争并存；两种竞争方式对竞争结果都会产生影响。当赤潮异弯藻初始接种密度不变（1×1 0 4 c e l l·m L - 1），石莼初始接种重量较低时（0 . 0 5 g / 1 5 0 m L），石莼和赤潮异弯藻的生长主要受干扰性竞争的影响；石莼初始接种重量较高时（0 . 4 g / 1 5 0 m L），石莼的生长主要受到利用性竞争的影响，而此时赤潮异弯藻的生长同时受到干扰性竞争和利用性竞争的影响。当石莼初始接种重量不变（0 . 0 5 g / 1 5 0 m L），赤潮异弯藻接种初始密度较低时（0 . 5×1 0 4 c e l l·m L - 1和1 . 0×1 0 4 c e l l·m L - 1），石莼和赤潮异弯藻的生长主要受干扰性竞争的影响；赤潮异弯藻初始接种密度较高时（2. 0×1 0 4 c e l l·m L - 1和4 . 0×1 0 4 c e l l·m L - 1），二者的生长同时受到利用性竞争和干扰性竞争的共同影响。试验结果说明石莼的初始接种重量和赤潮异弯藻初始密度可能是决定二者竞争方式的主要原因。（2）对石莼和赤潮异弯藻的相互作用、培养液滤液和胞内物质的交叉培养进行研究，结果表明：石莼抑制赤潮异弯藻的生长，赤潮异弯藻亦会抑制石莼的生长，二者之间存在克生效应：石莼主要通过分泌次生物质来抑制赤潮异弯藻的生长，而赤潮异弯藻对石莼生长的抑制可能通过细胞的直接接触和分泌次生物质完成的，其抑制物存在于藻体和培养液中。二、石莼-赤潮异弯藻相互作用对UV-B辐射的响应研究（1）研究了U V - B辐射对石莼和赤潮异弯藻的生长、叶绿素a含量、脱镁叶绿素a含量和石莼孢子萌发率的影响。结果表明：在单养的条件下，UV-B辐射对石莼和赤潮异弯藻的生长都有明显的抑制作用；而在混养的条件下，UV-B辐射对石莼生长的影响并不明显，但是却能显著抑制赤潮异弯藻的生长。石莼和赤潮异弯藻的叶绿素a和脱镁叶绿素a含量对U V - B辐射和克生效应有明显的响应，而且叶绿素a和脱镁叶绿素a含量的变化有一定的相似性。在U V - B辐射条件下，单养和与赤潮异弯藻混养石莼孢子的萌发率均受到明显的抑制，但未加U V - B辐射的与赤潮异弯藻混养的石莼孢子的萌发率虽然会下降，但是不明显。（2）石莼和赤潮异弯藻的抗氧化系统活性对UV-B辐射有明显的响应。在UV-B辐射处理的单养条件下，石莼丙二醛（MDA）含量，总抗氧化能力（T-AOC）和超氧化物岐化酶（T-SOD）活性显著升高，而可溶性蛋白含量和谷胱甘肽过氧化酶（GPX）活性显著降低；赤潮异弯藻MDA含量，T-AOC和过氧化氢酶（CAT）活性显著升高，而T-SOD活性，可溶性蛋白和类胡萝卜素（Car）含量显著降低。在混养的条件下，石莼MDA含量，T-AOC，CAT和T-SOD活性显著升高，而GPX活性显著下降；赤潮异弯藻CAT活性显著上升，而MDA含量，T-AOC，T-SOD和GPX活性显著下降。在混养附加UV-B辐射处理的条件下，石莼MDA含量，T-AOC，CAT和T-SOD活性显著升高，而GPX活性和Car含量显著降低；赤潮异弯藻CAT活性显著上升，而可溶性蛋白，MDA和Car含量，T-AOC，T-SOD和GPX活性显著下降。（3）采用生化检测法和聚丙烯酰胺凝胶电泳技术（PAGE）对石莼-赤潮异弯藻的两种同功酶—过氧化物酶（PRX）和多酚氧化酶（PPO）进行检测。结果显示：在单养条件下，UV-B辐射会使石莼和赤潮异弯藻PRX和赤潮异弯藻PPO活性降低，而石莼PPO活性却显著升高。混养会使石莼PPO活性显著下降，而赤潮异弯藻PPO活性显著升高。混养的同时附加UV-B辐射的条件下，石莼PRX和赤潮异弯藻PRX和PPO活性都受到了显著的抑制。不同处理组的石莼和赤潮异弯藻PRX、PPO同功酶谱均存在差异，主要表现为条带多少和活性强弱的不同，说明UV-B辐射处理和藻间的相互作用均能够引起石莼和赤潮异弯藻PRX和PPO同功酶谱的变化。（4）对石莼和赤潮异弯藻的胞外滤液的研究结果表明：胞外微生物对石莼-赤潮异弯藻相互作用无明显影响。石莼可以分泌热敏感的胞外物质来影响赤潮异弯藻的生长。UV-B辐射并不能减少赤潮异弯藻产生的有害物质，而与石莼混养会显著的减少赤潮异弯藻所产生的有害物质。（5）N、P限制对石莼-赤潮异弯藻相互作用有明显的影响。N、P限制的条件下，石莼生长受到UV-B辐射胁迫和赤潮异弯藻的克生作用在减小；而赤潮异弯藻生长受到UV-B辐射胁迫和石莼的克生作用会增加。更多还原

【Abstract】 Globally, the problem of red tide has expanded considerably over the lastseveral decades and seriously threatens the marine sustainability. It not only causesserious destruction to marine ecosystem and the recreational activities, but also leadsto massive mortality of the wild and farmed fisheries. Various methods have beenproposed on red tide controlling or mitigation, among which biological strategies arethe most potential one. Marine macroalga, for instance, is one of the potentialcandidates in red tide mitigation. It could inhibit the red tide micrialgal growth eitherby nutrient competition ability or by allelopathy. Ozone depletion is another seriousenvironmental problem that results in UV-B (280nm~320nm) radiation enhancement,and the enhancement would seriously damage the sustainability of marineecosystem.A macroalga Ulva pertusa Kjellm and a red tide microalga Heterosigmaakashiwo (hada) hada were selected to identify their interactions under controlledlaboratory conditions with and without UV-B radiation in the present study. Resultsshowed that:1、Interaction between U. pertusa and H. akashiwo with absence of UV-B radiation(1) The interspecific competition between U. pertusa and H. akashiwo wereestimated under different initial nutrient and biomass conditions. Results showedthat: Both exploitation competition and interference competition were found in theinteraction between U. pertusa and H. akashiwo. Interference competition playdominant role in the growth of U. pertusa and H. akashiwo when the initial biomassof was set at 0.05g/150mL for U. pertusa and 1×104cell·mL-1 for H. akashiwo ;however U. pertusa was affected by exploitation competition and H. akashiwo wasaffected by both exploitation and interference competition when the initial biomass of U. pertusa increased to 0.40g/150mL. When fixed the initial biomass of U. pertusa at 0.05g/150mL and changed the intial cell density of H. akashiwo we found that H. akashiwo was affected by interference competition under lower initial cell density (0.5×104cell·mL-1 and 1.0×104cell·mL-1) while affected by both exploitation and interference competition under higher initial cell density (2.0×104cell·mL-1and 4.0×104cell·mL-1). Result suggested that the initial inoculated biomass was responsible for different interspecific competition in mixed culture.(2) The simultaneous assay on culture was carried out in mixed culture. Results showed that: U. pertusa could inhibit the growth of H. akashiwo, H. akashiwo could inhibit the growth of U. pertusa simultaneously. Results suggested an allelopathic effect between their interactions: U. pertusa could release extracellular products to inhibit the growth of H. akashiwo, while direct cell-cell contact and releasing extracellular products were responsible for inhibitory effect of H. akashiwo on U. pertusa. U. pertusa and H. akashiwo could release intracellular products into the culture medium filtrates to affect the other’s growth.2、The responses of interaction between U. pertusa and H. akashiwo to UV-B radiation(1) Effects of UV-B radiation on the growth, Chl-a contents, pheapigment-a contents and sporulation of U. pertusa and H. akashiwo were studied. Results showed that: The allelopathic effect existed between U. pertusa and H. akashiwo. UV-B radiation could inhibit the growth of U. pertusa and H. akashiwo. However, UV-B radiation exhibited inhibition that was insignificant to the growth of U. pertusa but significant to the growth of H. akashiwo. The response of UV-B radiation on Chl-a and pheapigment-a contents were significant, and the changes of Chl-a and pheapigment-a contents showed comparability. UV-B radiation could inhibit the sporulation of U. pertusa. H. akashiwo could also inhibit the sporulation of U. pertusa, but it was insignificant.(2) The antioxidant enzymatic activies of U. pertusa and H. akashiwo changed greatly when exposed to UV-B radiation. Malondine (MDA) contents, tota1 antioxide capacity (T-AOC) and total superoxide dismutase (T-SOD) activities in U. pertusa increased significantly while just the opposite changes were observed in the soluble protein contents and glutathione peroxidase (GPX) activity in U. pertusa. MDA contents, T-AOC and catalase (CAT) activities in H. akashiwo increased significantly, but its T-SOD activity, soluble protein and carotenoid (Car) contents in H. akashiwo decreased obviously when exposed to the UV-B radiation. As to mixed culture, MDA contents, T-AOC, CAT and T-SOD activities in U. pertusa increased significantly, but the GPX activity in U. pertusa decreased significantly. CAT activity in H. akashiwo increased significantly, but MDA contents, T-AOC, T-SOD and GPX activities in H. akashiwo decreased obviously in mixed culture. MDA contents, T-AOC, CAT and T-SOD activities in U. pertusa increased significantly, but GPX activity and Car contents in U. pertusa decreased significantly in mixed culture exposed to UV-B radiation. CAT activity in H. akashiwo increased significantly, but MDA and Car contents, T-AOC, T-SOD and GPX activities in H. akashiwo decreased significantly in mixed culture under UV-B radiation.(3) Furthermore, biochemical method and the vertical polyacrylamide gel electrophoresis (PAGE) were used to identify the isozymes differentiation of peroxidase (PRX) and polyphenol peroxidase (PPO) in U. pertusa and H. akashiwo. Results showed that: PRX activity in U. pertusa and H. akashiwo decreased significantly when exposed to UV-B radiation. PPO activity in U. pertusa increased obviously while just the opposite changes were observed in H. akashiwo when exposed to UV-B radiation. PPO activity in U. pertusa decreased significantly, but PPO activity in H. akashiwo increased significantly in mixed culture. PRX activity in U. pertusa and PRX and PPO activities in H. akashiwo decreased significantly in mixed culture under UV-B radiation. The isozymes of PRX and PPO in U. pertusa and H. akashiwo presented differences respectively in forms of numbers of bands and staining intensity. Therefore, UV-B radiation and the interaction between U. pertusa and H. akashiwo could result in changes of PRX and PPO isozymes.(4) The extracellular products of U. pertusa and H. akashiwo were studied. Results showed that: Effects of extracellular microbe on the interaction between U. pertusa and H. akashiwo was insignificant. The thermo-sensitive products were excreted by U. pertusa which could inhibit the growth of H. akashiwo. UV-B radiation could not alleviate the deleterious products from H. akashiwo, but the deleterious products from H. akashiwo could be alleviated in mixed culture with U. pertusa.(5) Effects of N and P limitation on the interaction between U. pertusa and H. akashiwo were significant. Effects of UV-B radiation stress and allelopathic effect from H. akashiwo on the growth of U. pertusa were decreased under the condition of N and P limitation. Nevertheless effects of UV-B radiation stress and allelopathic effect from U. pertusa on the growth of H. akashiwo were increased under the condition of N and P limitation.更多还原