秦皇岛近海浮游植物群落结构变化及其组学研究

	秦皇岛近海浮游植物群落结构变化及其组学研究
	许歆
学位类型	博士
导师	俞志明 ; 宋秀贤
	2017-05
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	环境科学
关键词	秦皇岛近海浮游植物群落生态特征宏基因组学宏转录组学
其他摘要	秦皇岛地处渤海西部，与渤海海峡口相对，是享誉国内外的著名旅游城市。然而，近年来受渤海整体生态环境不断恶化的影响，秦皇岛近海藻华发生情况日趋严重。尤其自2009年开始，连年暴发的抑食金球藻（Aureococcus anophagefferens）褐潮给当地的扇贝养殖业和滨海旅游业带来巨大的经济损失，但目前对其暴发的环境特点和科学机制了解不足。为了探索该海域浮游植物群落演替的内在和外在驱动因子，更深入地了解该海域有害藻华的形成特点与机制，本研究于2013年3月~2014年1月期间在秦皇岛褐潮发生海域进行了综合调查，通过现场调查和室内实验，采用形态学鉴定、叶绿素a（chlorophyll a，Chl-a）浓度测定、流式细胞仪计数、宏基因组学和宏转录组学等技术，对该海域浮游植物群落的结构特点、变化特征以及对环境的响应等方面进行了研究。显微镜检共鉴定浮游植物56属123种。其中，硅藻39属87种，甲藻16属33种，金藻、裸藻、绿藻各1种。浮游植物优势种群呈现从微型链状硅藻到甲藻（春季），到小型硅藻（夏季），再到微型链状硅藻（秋季和冬季）的季节性变化现象。典范对应分析的结果显示，调查期间该海域硅藻和甲藻的细胞丰度分别对营养盐浓度和水温的变化比较敏感。为了更好地了解浮游植物群落的粒级结构，本论文通过分级Chl-a浓度测定和流式细胞仪计数的方法进行了分析。分级Chl-a浓度的测定结果表明，浮游植物的粒级生物量主要由微型和小型浮游植物贡献。流式细胞仪计数的结果显示，10 μm以下的浮游植物在调查期间细胞丰度较高（>10⁸ cells/L），是显微镜检结果的10000倍，说明10 μm以下的浮游植物主要由显微镜检难以观察到的微微型浮游植物组成。抑食金球藻的细胞丰度在8、9月份最高，但总体上在10 μm以下浮游植物类群中占的比例较小（3.83~22.90%）。 18S rDNA测序技术从分子生物学角度分析了真核浮游植物群落（包括微微型浮游植物）的物种组成和相对丰度。结果共鉴别出71种藻，其中有34种之前未曾在渤海报道过。鉴别出的藻种中有36种有害藻华种，且其中11种为渤海新纪录种。此外，在属和种水平上的分析结果均显示，具有较高序列丰度的藻类大部分为微型或者微微型浮游植物。为了了解秦皇岛近海浮游植物群落演替及藻华形成过程中的功能反应，本研究采用宏转录组学技术进行了分析。结果显示，10 μm以下的浮游植物是藻类基因表达的主要贡献者。在不同时期，不同浮游植物光合作用（Photosynthesis）、光合作用-天线蛋白（Photosynthesis-antenna proteins）、吞噬体（Phagosome）及溶酶体（Lysosome）通路的基因表达有差异。浮游植物编码磷酸盐转运蛋白和碱性磷酸酶的基因具有多样性和物种特异性。此外，大多数基础代谢通路在藻华发展与消亡过程中的表达水平高于藻华发生期间。综上所述，本论文利用多种技术手段，综合研究了秦皇岛近海以微微型浮游植物为优势种群的群落结构特点，发现了大量渤海新纪录藻种，拓宽了对渤海真核浮游植物群落结构、组成和生物量的认识，阐释了秦皇岛近海真核浮游植物群落的演替特点，为揭示该海域的生态系统演变和藻华形成机理提供科学依据。 ; Qinhuangdao, located along the western boundary of the Bohai Sea and opposite to the Bohai Strait, is a tourist city that is well known both within China and abroad. In recent years, due to the deterioration of the ecological environment in the Bohai Sea, harmful algal blooms have become more and more serious. Since 2009, the newly recorded species Aureococcus anophagefferens has successively induced brown tides in the Qinhuangdao coastal waters, causing significant damage to the local shellfish industry and coastal tourism. However, studies about the outbreak mechanism of brown tides and environmental characteristics of the Qinhuangdao coastal waters have rarely been reported. Here, in order to explore the internal and external factors driving community succession and to provide a scientific basis for the further explanation of the outbreak mechanism of harmful algal blooms, we conducted a series of studies about the characteristics of the phytoplankton community and its responses to environmental changes from March 2013 to January 2014, using microscopy techniques, chlorophyll a (Chl-a) analyses, flow cytometry, 18S rDNA sequencing and metatranscriptome sequencing. In total, 123 species of phytoplankton belonging to 56 genera were identified via microscopy, including 87 species of diatom belonging to 39 genera, 33 species of dinoflagellate belonging to 16 genera, and 1 species each of chlorophyte, euglenophyte and chrysophyte. The phytoplankton community underwent succession from nano-celled chained diatoms to dinoflagellates in the spring and summer, followed by succession to micro-celled diatoms and nano-celled chained diatoms as the most prominent groups in the subsequent autumn and winter. Canonical correspondence analysis revealed that changes in the abundance of diatoms were related to nutrient availability, whereas water temperature was the crucial factor influencing the abundance of dinoflagellates. To better study the size-fractionated composition of the phytoplankton community, Chl-a analyses and flow cytometry were applied. Analyses of the size-fractionated Chl-a concentration showed that micro- and nanophytoplankton represented the majority of total Chl-a. During the study period, phytoplankton < 10 μm had high cell abundance (>10⁸ cells/L), which was more than 10,000 times the result observed using microscopy. As picophytoplankton are difficult to distinguish and count by microscopy, the results above indicate the predominance of picophytoplankton in the group of phytoplankton < 10 μm. A. anophagefferens had high cell abundances in August and September and contributed small proportions (3.83% to 22.90%) of the phytoplankton < 10 μm during the study period. To evaluate the species composition and relative abundance of the eukaryotic phytoplankton community (including the picophytoplankton) from a molecular biological perspective, we sequenced 18S rRNA genes extracted from field samples. A total of 71 algal species were identified, among which 34 were new records. Further analysis revealed that half of the identified species were known bloom-forming or toxic algae, including 11 harmful algal species that were previously undetected or unreported in the Bohai Sea. Dinoflagellates stood out from the phytoplankton community in many respects, including sequence abundance, OTU richness, new records, harmful algal species and nutritional modes. The more abundant genera among different phytoplankton lineages were almost pico- or nano-celled algae, as were the most abundant identified algal species. A metatranscriptomics technique was employed to reveal the functional responses during the phytoplankton succession in the Bohai Sea. Results showed that phytoplankton < 10 μm had high contributions to the gene expression in the phytoplankton community. Expression levels of the pathways Photosynthesis, Photosynthesis-antenna proteins, Phagosome and Lysosome varied among algal species and samples. Pre- and post- bloom gene expression levels of most basal metabolic pathways were higher than those during the bloom. In summary, we used a variety of techniques to study the characteristics of the phytoplankton community in the Qinhuangdao coastal waters and found that picophytoplankton formed a dominant group. Many algal species were newly recorded in the Bohai Sea, broadening our understanding about the composition and biomass of the eukaryotic phytoplankton community. Moreover, we described the succession characteristics of the eukaryotic phytoplankton community in the Qinhuangdao coastal waters, providing a scientific basis for revealing the processes underlying the evolution of the ecosystem and revealing the mechanism of algal bloom formations.
学科领域	海洋科学
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/136686
专题	海洋生态与环境科学重点实验室
作者单位	1.中国科学院海洋研究所 2.中国科学院大学
推荐引用方式 GB/T 7714	许歆. 秦皇岛近海浮游植物群落结构变化及其组学研究[D]. 北京. 中国科学院大学,2017.

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