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151.
生活于珊瑚礁区的大型海藻可以与珊瑚一起为礁栖生物提供食物和栖息地, 它们在维护珊瑚礁生态系统生物多样性中起着极为重要的作用。本论文比较研究了生活于我国南海中沙大环礁区4种优势海藻的生化组分、光合特征及其对海水升温的生理响应,其中厚膜藻(Grateloupia ellipitica)和粉枝藻(Liagora samaensis)为红藻, 钙扇藻(Udotea flabellum)和仙掌藻(Halimeda discoidea)为绿藻。结果显示, 与绿藻相比, 红藻藻体叶绿素(Chl a)和类胡萝卜素含量更低且含有藻胆素, 红藻的光补偿点(EC)和呼吸速率(Rd)均显著低于绿藻。海水升温提高了4种海藻的光能利用效率(α)、EC、Rd和日净光合固碳量; 同时, 升温还降低红藻的饱和光强(EK)、提高绿藻的最大光合放氧速率(Pmax)。结果还显示, 海水升温在光强较低时提高红藻的光合放氧速率, 光强较高时则降低其放氧速率; 升温也提高绿藻的光合放氧速率, 但光强变化对升温效应的影响不显著。基于4种海藻的光生理特征以及升温效应的种间差异性可见, 短时间升温(~4℃)有利于中沙大环礁区海藻的光合作用; 与绿藻相比, 该升温效应更有利于红藻。 相似文献
152.
海底管道一旦受到坠物撞击损伤,会造成严重的环境污染及经济损失,为保证管道在运行期间的安全性,常对其进行埋深处理。对于有埋深的海底管道,坠物的撞击会造成管道上覆土体的大变形,在数值模拟中会导致网格畸变,甚至无法收敛。耦合欧拉-拉格朗日法(CEL法)可有效处理土体大变形问题,本文基于此方法建立了坠物-管道-土体有限元模型,分析了坠物撞击速度、质量、形状、海床土体性质(弹性模量、内摩擦角、黏聚力)、埋深对海底管道塑性变形的影响。结果表明,管道的凹痕深度随坠物撞击速度和质量的增加而增加;坠物与海床土体及管道接触面积越小,管道的凹痕深度越大;管道的埋置深度及海床土体的性质对吸收坠物的撞击能量有直接关系:海床土体的强度越高、埋深越大,管道所受到的损伤程度越小。分析结果可为管道的设计与防护工作提供科学依据,且与现行规范比较,本文方法更加经济、合理。 相似文献
153.
为促进我国海洋渔业的可持续发展,文章基于面板数据回归模型,分析海洋渔业产业结构的优化。研究结果表明:我国海洋渔业发展趋势较好,但受政策和资源等因素的制约,亟须优化产业结构;海洋渔业产业结构优化与海水养殖与海洋捕捞的增加值之比存在正相关关系,与海水养殖与海洋渔业的从业人员数量之比存在负相关关系;应提高海水养殖增加值,促进养殖企业形成最佳规模,同时重视先进科技的支撑作用。 相似文献
154.
ZHAO Mingliang WEI Xianfeng LIU Xuemeng DONG Xueyang YU Rilei WAN Shengbiao JIANG Tao 《中国海洋大学学报(英文版)》2018,(3)
Due to their structural diversity and variety of biological activities, marine natural products have been the subject of extensive study. These compounds, especially phospholipid polycyclic aromatic hydrocarbons, have a wide range of pharmacological applications, including embedded DNA and central nervous system, anti-tumor, anti-virus, anti-parasite, anti-bacterial, and antithrombotic effects. Unfortunately, the insufficient drug sources have limited the development of these compounds. In this study, we isolated salinpostin compounds from a fermentation solution of marine-derived Salinospora sp., which has a common bicyclic enol-phosphotriester core framework, as well as potent and selective antimalarial activities against P. falciparum with EC_(50)=50 nmolL~(-1). The chemical synthesis of these compounds in greater quantities is necessary for their use in bioactivity studies. Thus we explored a short route with high yields and mild reaction conditions, which can generate combinatorial libraries for drug discovery and lead optimization. We developed a new total synthesis method for six cyclic enol-phosphotriester salinipotin compounds and their diastereomers. For the total synthesis of cyclipostin P, we prepared cyclic enol-phosphotriester salinipostin compounds in 10 steps from a readily accessible starting material, 1,3-dihydroxyacetone, and obtained an overall yield of 1.29%. We fully characterized these compounds by proton nuclear magnetic resonance(~1H-NMR), carbon-13 NMR(~(13)C-NMR), and high-resolution mass spectrometry(HRMS) analyses, and found they coincide absolutely with the same compounds reported previously. 相似文献
155.
XIA Shaohong CAO Jinghe SUN Jinlong LV Jinshui XU Huilong ZHANG Xiang WAN Kuiyuan FAN Chaoyan ZHOU Pengxiang 《中国海洋大学学报(英文版)》2018,(1)
The northern margin of the South China Sea, as a typical extensional continental margin, has relatively strong intraplate seismicity. Compared with the active zones of Nanao Island, Yangjiang, and Heyuan, seismicity in the Pearl River Estuary is relatively low. However, a ML4.0 earthquake in 2006 occurred near Dangan Island(DI) offshore Hong Kong, and this site was adjacent to the source of the historical M5.8 earthquake in 1874. To reveal the seismogenic mechanism of intraplate earthquakes in DI, we systematically analyzed the structural characteristics in the source area of the 2006 DI earthquake using integrated 24-channel seismic profiles, onshore–offshore wide-angle seismic tomography, and natural earthquake parameters. We ascertained the locations of NW-and NE-trending faults in the DI sea and found that the NE-trending DI fault mainly dipped southeast at a high angle and cut through the crust with an obvious low-velocity anomaly. The NW-trending fault dipped southwest with a similar high angle. The 2006 DI earthquake was adjacent to the intersection of the NE-and NW-trending faults, which suggested that the intersection of the two faults with different strikes could provide a favorable condition for the generation and triggering of intraplate earthquakes. Crustal velocity model showed that the high-velocity anomaly was imaged in the west of DI, but a distinct entity with low-velocity anomaly in the upper crust and high-velocity anomaly in the lower crust was found in the south of DI. Both the 1874 and 2006 DI earthquakes occurred along the edge of the distinct entity. Two vertical cross-sections nearly perpendicular to the strikes of the intersecting faults revealed good spatial correlations between the 2006 DI earthquake and the low to high speed transition in the distinct entity. This result indicated that the transitional zone might be a weakly structural body that can store strain energy and release it as a brittle failure, resulting in an earthquake-prone area. 相似文献
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159.
碱性玄武岩形成的时限及其地质意义 总被引:4,自引:0,他引:4
中国华北克拉通及邻区的早前寒武纪不存在碱性玄武岩。全球范围内碱性玄武岩的形成也存在时限性,它们在中新生代以来相对大量的出现。碱性玄武岩可划分为钾质碱性玄武岩和钠质碱性玄武岩两大类,后者还可作进一步划分。它们在同位素组成和元素组成上存在相互过渡的变化,这与地幔源区外来加入物质的种类和比例不同有关。高压和低程度熔融是所有碱性玄武岩形成的必要条件。研究表明,碱性玄武岩形成具时限性主要与地球热状态从热向冷的历史演化有关。碱性玄武岩的形成需要地幔俯冲作用,可达到相当深度的地幔俯冲作用只是到了太古宙以后才发生,并在中新生代以来达到高潮。 相似文献
160.