海洋生态与环境科学重点实验室知识库

近年来，北部湾海域富营养化问题日趋严重，球形棕囊藻（Phaeocystis globosa）赤潮频繁发生，影响局域海洋生态系统及人类经济社会活动。本研究基于2016年9月至2017年8月和2018年11月至2019年4月在北部湾北部海域开展的月度多学科综合调查，系统研究了北部湾北部海域球形棕囊藻囊体时空分布特征及其与主要环境因子的关系，解析了球形棕囊藻赤潮高发区水体异养细菌丰度的动态变化规律，阐述了球形棕囊藻赤潮过程中颗粒附着和浮游原核生物群落时空分布特征及其与主要环境因素的关系。主要结果如下：

（1）北部湾北部海域球形棕囊藻囊体时空分布及其影响因素  调查期间囊体丰度介于0–18.98 × 10⁴ col·m^-3，囊体丰度峰值出现在冬季月（2017年2月和2019年1月）。随着时间的推移，囊体丰度高值区首先出现在从涠洲岛附近海域（2016年12月和2018年11月），再出现在钦州湾–北海附近海域（2017年2月和2019年1月），最后出现在琼州海峡–涠洲岛海域（2017年3月和2019年2月）。水温和盐度是影响囊体时空分布的主要环境因素，在局部区域丰富的硝酸盐和磷酸盐为囊体的形成奠定了基础。球形棕囊藻囊体丰度与其他浮游植物丰度显著正相关，其他浮游植物群落结构的改变也会影响囊体时空分布。

（2）北部湾北部海域水体异养细菌时空分布特征  2016年9月至2017年8月，该海区异养细菌丰度介于（2.75–56.86）× 10⁵ cell·mL^-1，平均值（11.01 ± 6.31）× 10⁵ cell·mL^-1，存在明显月际变化，各季节细菌丰度从高至低依次为：夏季（6月、8月和9月）、冬季（12月、1月和2月）、春季（3月和4月）、秋季（11月）。异养细菌丰度由近岸浅水区向远岸深水区逐渐降低；在近岸浅水区异养细菌丰度垂直分布均匀，在水深大于20 m的海区出现季节性分层现象：表层异养细菌丰度高于底层。异养细菌时空分布差异取决于环境条件的变化，尤其是温度、盐度、叶绿素a和溶解氧含量对其有重要影响。除3月、6月和8月外，异养细菌丰度与营养盐呈显著负相关，二者关系受到浮游植物的间接影响。除此之外，在囊体存在时期，异养细菌丰度还与球形棕囊藻囊体丰度密切相关。

（3）北部湾球形棕囊藻赤潮高发期颗粒附着和浮游原核生物群落组成与结构  2016年12月至2017年2月调查期间，北部湾北部海域优势原核生物为变形菌门、蓝细菌门、奇古菌门、疣微菌门、广古菌门、放线菌门和拟杆菌门。颗粒附着原核生物群落和浮游原核生物群落在组成和结构上都存在显著差异，前者更多样化，也更不稳定。原核生物群落组成和结构都存在着明显的月际变化，均与溶解氧、铵盐、磷酸盐和溶解有机碳密切相关；相比于附着原核生物群落，浮游原核生物群落对球形棕囊藻丰度的变化更为敏感。红杆菌科、交替单胞菌目、波尔蒂球菌科、弧菌属、黄杆菌目和疣微菌纲是球形棕囊藻赤潮暴发期和衰退期原核生物群落的优势类群，可能在降解藻源有机质方面发挥重要作用。

（4）北部湾球形棕囊藻赤潮暴发期原核生物群落空间分布与昼夜变化  2019年1月北部湾球形棕囊藻赤潮暴发期间，原核生物群落在空间分布上呈现明显的水平差异，而垂向结构相似。空间距离和环境因素共同决定了原核生物群落结构的水平分布，而环境因素的影响更强烈，尤其是球形棕囊藻囊体丰度和叶绿素a浓度与原核生物群落关系最为密切。冬季强烈的水体垂直混合破坏了原核生物群落垂直结构的异质性。附着原核生物群落结构昼夜差异显著，而浮游原核生物群落结构昼夜差异不显著。水体中无机氮浓度和球形棕囊藻囊体丰度是影响赤潮暴发期原核生物群落昼夜变化的主要环境因素。

综上，本论文系统地研究了北部湾北部海域球形棕囊藻囊体时空分布特征及其与主要环境因素的关系；揭示了球形棕囊藻赤潮高发区水体异养细菌丰度的时空分布特征及其与主要环境因素的关系；首次报道了北部湾球形棕囊藻赤潮高发区颗粒附着和浮游原核生物群落组成和结构的差异；揭示了球形棕囊藻赤潮暴发期原核生群落组成和结构的空间分布与昼夜变化。相关研究结果丰富了对北部湾球形棕囊藻赤潮过程的认识，为深入研究球形棕囊藻赤潮的生消机制及球形棕囊藻赤潮监测预警提供了数据支撑和理论依据，并为进一步研究原核生物在球形棕囊藻赤潮消长过程中的生态影响奠定了基础。

Due to the increasingly serious eutrophication in the Beibu Gulf, Phaeocystis globosa blooms occur frequently, and impairs marine ecosystem and social economy in recent years. The spatio-temporal distribution of P. globosa colonies and its relationship with main environmental factors were studied based on the monthly multi-disciplinary investigations from September 2016 to August 2017 and from November 2018 to April 2019. Furthermore, the heterotrophic bacteria dynamics in high-incidence area of P. globosa blooms were analyzed, and the spatio-temporal distribution of particle-attached and free-living prokaryotic communities during P. globosa blooms and the relationship with main environmental factors were discussed as well. The main findings were as follows:

(1) The spatio-temporal distribution of P. globosa colonies and related environmental factors in the northern Beibu Gulf  During the survey period P. globosa colony abundance ranged from 0 to 18.98 × 10⁴ col·m^-3. The colony abundance peaked in in winter months (February 2017 and January 2019). The high-colony-abundance zone was spatially different with time. It first appeared in the Weizhou Island surrounding waters (December 2016 and November 2018), then appeared in the Qinzhou - Beihai coastal waters (February 2017 and January 2019), and finally appeared in the Qiongzhou Strait - Weizhou Island waters (March 2017 and February 2019). It is indicated that temperature and salinity are main environmental factors affecting the spatio-temporal distribution of P. globosa colonies, and sufficient nitrate and phosphate facilitate the formation of P. globosa colonies in Qiongzhou Strait - Weizhou Island waters. The P. globosa colony abundance was positively correlated with other-phytoplankton abundance, and its spatio-temporal distribution was influenced by the succession of other-phytoplankton community.

(2) The spatio-temporal distribution of heterotrophic bacteria in the northern Beibu Gulf  From September 2016 to August 2017, the heterotrophic bacteria abundance ranged in (2.75–56.86) × 10⁵ cell·mL^-1, with an average of (11.01 ± 6.31) × 10⁵ cell·mL^-1. There were obvious monthly variations, and the heterotrophic bacteria abundance in each season from high to low was: summer (June, August and September), winter (December, January and February), spring (March and April), and autumn (November). Heterotrophic bacteria were densely distributed in the shallow coastal water, and gradually reduced in the deep offshore water. The vertical distribution of heterotrophic bacteria was evenly distributed in the coastal areas, while the seasonal vertical heterogeneity occurred in the areas deeper than 20 m, where the bacteria abundance was higher at surface than at bottom. The spatio-temporal distribution of heterotrophic bacteria was controlled by the environmental conditions, especially the temperature, salinity, chlorophyll a, and dissolved oxygen. Correlations between inorganic nutrients and heterotrophic bacteria abundance were significantly negative in some months, when the phytoplankton indirectly affected them. In addition, the heterotrophic bacteria abundance was also closely related to the P. globosa colony abundance in the period of colony existence.

(3) Particle-attached and free-living prokaryotic community composition and structure during the Phaeocystis globosa bloom in the Beibu Gulf  From December 2016 to February 2017, the dominant phyla in the northern Beibu Gulf were Proteobacteria, Cyanobacteria, Thaumarchaeota, Verrucomicrobia, Euryarchaeota, Actinobacteria, and Bacteroidetes. The composition and structure of PA and FL prokaryotic communities were significantly different. The PA fraction was more diverse and unstable temporally compared to the FL fraction. The variations in the composition and structure of the prokaryotic community were closely associated with major environmental variables, particularly DO, NH₄⁺, PO₄^3-, and DOC. The FL fraction was more sensitive to P. globosa than the PA fraction. Rhodobacteraceae, Alteromonadales, Porticoccaceae, Vibrio, Flavobacteriales, and Verrucomicrobiae were the key prokaryotic groups during the outbreak and recession of P. globosa blooms. They could play important roles in degrading the algal-derived organic matter.

(4) Spatial and diel variations of the prokaryotic community in the Phaeocystis globosa blooms area of Beibu Gulf  During the outbreak of P. globosa blooms in January 2019, the distributions of prokaryotic communities varied significantly in the horizontal direction, while slightly in the vertical direction. Both spatial distance and environmental variables, particularly P. globosa colony abundance and Chl a, shaped the horizontal distribution of the prokaryotic community structure. The vertical heterogeneity of the prokaryotic community was disrupted by the strong vertical mixing of the water column in winter. PA prokaryotic communities showed significant diel variations, but the diel variations of FL prokaryotic communities were insignificant. Inorganic nitrogen and P. globosa colony abundance were the main environmental variables impacting the diel variations of prokaryotic communities.

In conclusion, this dissertation studied the spatio-temporal distribution of P. globosa colonies and heterotrophic bacteria, and their relationships with main environmental factors were discussed. Furthermore, the differences in the composition and structure of particle-attached and free-living prokaryotic communities during the P. globosa bloom in the Beibu Gulf were studied, and the spatial and diel variations of the prokaryotic community in the P. globosa bloom area of Beibu Gulf were revealed. The results are helpful for better understanding P. globosa blooms in Beibu Gulf, and provide fundamental data and evidence to further elucidate the initiation and termination of P. globosa blooms and to monitor and predict the occurrence of P. globosa blooms in the area, and to further reveal the ecological impact of prokaryotes during P. globosa blooms.

第1章 绪论... 1

1.1  北部湾环境特征及赤潮演变趋势概况... 1

1.2  球形棕囊藻赤潮及其危害研究概况... 2

1.3  不同环境因素对球形棕囊藻赤潮消长过程的影响... 8

1.3.1  物理因素... 8

1.3.2  营养盐... 10

1.3.3  生物因素... 11

1.4  海洋原核生物及其在生物地球化学循环中的作用... 12

1.5  不同环境因素对海洋原核生物群落组成和结构的影响... 15

1.5.1  非生物因素... 16

1.5.2  生物因素... 17

1.6  球形棕囊藻赤潮与原核生物群落的关系... 17

1.6.1  原核生物在赤潮消长过程中的作用... 19

1.6.2  原核生物在球形棕囊藻赤潮消长过程中的作用... 20

1.7  研究目的、内容及意义... 21

第2章 北部湾北部海域球形棕囊藻囊体时空分布及其影响因素... 23

2.1  前言... 23

2.2  材料与方法... 24

2.2.1  航次信息... 24

2.2.2  样品采集与分析... 25

2.2.3  数据来源... 26

2.2.4  数据处理与统计分析... 26

2.3  结果... 27

2.3.1  水文环境特征... 27

2.3.2  球形棕囊藻囊体时空分布特征... 31

2.3.2.1  球形棕囊藻囊体丰度及直径月际变化... 31

2.3.2.2  球形棕囊藻囊体时空分布... 32

2.3.3  球形棕囊藻囊体丰度与环境因素的关系... 33

2.3.4  浮游植物（球形棕囊藻除外）群落结构特征分析... 35

2.3.4.1  浮游植物群落物种组成... 35

2.3.4.2  浮游植物总细胞丰度的分布... 39

2.3.4.3  硅藻细胞丰度的分布... 41

2.3.4.4  甲藻细胞丰度的分布... 42

2.3.4.5  浮游植物群落特征指数分布... 43

2.3.5  球形棕囊藻囊体丰度与其他浮游植物群落的关系... 45

2.4  讨论... 51

2.4.1  球形棕囊藻囊体时空分布与环境因素的关系... 51

2.4.1.1  球形棕囊藻囊体与温度和盐度的关系... 51

2.4.1.2  球形棕囊藻囊体与叶绿素a的关系... 52

2.4.1.3  球形棕囊藻囊体与营养盐的关系... 52

2.4.2  球形棕囊藻囊体时空分布与其他浮游植物的关系... 53

2.4.2.1  球形棕囊藻囊体与硅藻的关系... 53

2.4.2.2  球形棕囊藻囊体与甲藻的关系... 54

2.5  小结... 55

第3章 北部湾北部海域水体异养细菌时空分布特征... 57

3.1  前言... 57

3.2  材料与方法... 58

3.2.1  航次信息... 58

3.2.2  样品采集与处理... 59

3.2.3  数据来源... 59

3.2.4  数据处理与统计分析... 60

3.3  结果... 60

3.3.1  水文环境特征... 60

3.3.2  异养细菌丰度时空分布特征... 67

3.3.2.1  异养细菌丰度月际变化... 67

3.3.2.2  异养细菌丰度水平分布... 68

3.3.2.3  异养细菌丰度垂直分布... 71

3.3.3  异养细菌丰度与环境因素的关系... 72

3.3.3.1  异养细菌丰度与水体理化因子的关系... 72

3.3.3.2  异养细菌丰度与网采球形棕囊藻囊体丰度的关系... 73

3.4  讨论... 74

3.4.1  异养细菌丰度变化特征... 74

3.4.2  异养细菌丰度分布差异... 76

3.4.3  异养细菌丰度与环境因素之间的关系... 77

3.4.3.1  异养细菌丰度与温度和盐度的关系... 77

3.4.3.2  异养细菌丰度与叶绿素a、溶解氧和pH的关系... 78

3.4.3.3  异养细菌丰度与营养盐的关系... 79

3.4.3.4  异养细菌丰度与球形棕囊藻囊体丰度的关系... 80

3.5  小结... 81

第4章 北部湾球形棕囊藻赤潮高发期颗粒附着和浮游原核生物群落组成与结构    83

4.1  前言... 83

4.2  材料与方法... 84

4.2.1  研究区域与航次信息... 84

4.2.2  样品采集与处理... 86

4.2.3  数据来源... 86

4.2.4  原核生物DNA提取、PCR扩增和测序... 86

4.2.5  数据处理与统计分析... 87

4.3  结果... 89

4.3.1  水文环境特征... 89

4.3.2  原核生物群落α-多样性和物种组成... 91

4.3.3  原核生物群落结构和显著性差异物种... 96

4.3.4  原核生物群落与环境因素之间的关系... 105

4.4  讨论... 109

4.4.1  附着和浮游原核生物群落多样性和组成的差异... 109

4.4.2  原核生物群落与环境因素的关系... 110

4.4.3  与球形棕囊藻赤潮相关的关键原核生物类群... 111

4.5  小结... 113

第5章 北部湾球形棕囊藻赤潮暴发期原核生物群落空间分布与昼夜变化    115

5.1  前言... 115

5.2  材料与方法... 116

5.2.1  航次信息及现场采样... 116

5.2.2  环境样品处理与分析... 117

5.2.3  数据来源... 118

5.2.4  原核生物DNA提取、PCR扩增和测序... 118

5.2.5  数据处理与统计分析... 118

5.3  结果... 119

5.3.1  水文环境特征... 119

5.3.2  原核生物群落空间分布及其与环境因素的关系... 125

5.3.2.1  空间样本组原核生物群落α-多样性及与环境因素的关系... 125

5.3.2.2  空间样本组原核生物群落物种组成... 129

5.3.2.3  空间样本组原核生物群落结构及与环境因素的关系... 131

5.3.3  原核生物群落昼夜变化及其与环境因素的关系... 136

5.3.3.1  昼夜样本组原核生物群落α-多样性及与环境因素的关系... 136

5.3.3.2  昼夜样本组原核生物群落物种组成... 138

5.3.3.3  昼夜样本组原核生物群落结构及与环境因素的关系... 140

5.4  讨论... 143

5.4.1  原核生物群落的空间分布... 143

5.4.2  原核生物群落的昼夜变化... 144

5.5  小结... 145

第6章 结论与展望... 147

6.1  结论... 147

6.2  创新点... 148

6.3  不足与展望... 148

参考文献... 151

致  谢... 171

作者简历及攻读学位期间发表的学术论文与研究成果  175