海洋生态与环境科学重点实验室知识库

  陆架边缘海虽然仅占全球海洋面积的8%，但在初级生产、有机碳埋藏和氮收支方面发挥着巨大作用。中国东部边缘海是重要的陆架边缘海之一，也是陆海相互作用及人类活动的强烈承受区域。近年来，中国近海低氧问题频发，不仅严重破坏海洋生态平衡，而且作用于海洋有机碳保存及活性氮去除，对海洋碳汇、氮收支乃至全球气候变化产生重要影响。反演过去的低氧和碳、氮循环演变过程是预测未来发展趋势并制定应对策略的基础。生物标志物作为目前反演过去环境变化的主要手段，建立灵敏可靠的生物标志物体系是准确重建长时间尺度下低氧和碳、氮循环演变历程的关键。细菌藿多醇（bacteriohopanepolyols，BHPs）是来源于细菌细胞膜脂的五环三萜类化合物，其组成和结构受到环境条件和细胞应激反应的调控，能够灵敏地响应和记录环境变化并在地质载体中稳定保存。尽管BHPs已表现出指示环境变化和生物活动的重要潜能，但目前对于海洋环境中BHPs的来源、沉降和保存过程仍缺乏了解，其作为生物标志物的可靠性和准确性还有待探究。本学位论文以渤、黄、东海海水颗粒物、表层沉积物和柱状沉积物为研究对象，解析了BHPs的来源、沉降和保存过程，在此基础上结合相关细菌群落结构、功能基因丰度以及微观培养实验，评估了BHPs作为环境代用指标在中国东部边缘海的可靠性和适用性，并将BHPs指标应用于沉积记录中反演了东海内陆架南部低氧区百年来低氧和氮循环的演变历程。获得的主要研究结论和认识如下：

1. 系统研究了中国东部边缘海海水颗粒物和表层沉积物中BHPs的来源、沉降和保存。发现不同BHPs组分具有典型的陆源和海源分布特征，海源的细菌藿四醇（BHT）和2-甲基BHT主要来源于水柱原位产生；沉积物中BHPs主要来源于水体原位沉降；BHPs整体上降解程度较低，其中BHT及其异构体（BHT-isomer）、2-甲基BHT相对优先保存；中国东部边缘海沉积有机质以海源有机质（MOM）为主，低氧环境有利于BHPs和有机碳的保存。

  中国东部边缘海海水颗粒物和表层沉积物中BHPs具有显著的来源特征和空间分布特征。海源自生来源的BHT呈现出由近岸到外海、由表层到底层逐渐增加的变化趋势，在外海底层海水中占比60%以上。BHT-isomer包括陆源细菌或淡水厌氧氨氧化菌Ca. Brocadia产生的BHT-34R和海洋厌氧氨氧化菌Ca. Scalindua特异性产生的BHT-x。BHT-34R仅存在于河口内及近岸海域表层海水中；而外海海域中BHT-isomer主要为BHT-x，其在深层高盐低氧海水中呈现高值。尽管可能存在其他潜在的细菌来源，2-甲基BHT被认为主要来源于表层海水中的固氮蓝细菌，呈现由近岸向外海增加的变化趋势。氨基藿四醇和氨基藿五醇主要来源于表层和底层海水中的好氧甲烷氧化菌，受到陆源输入和沉积物释放CH₄的共同驱动。陆地土壤细菌来源的腺苷-BHPs呈现由近岸到外海、由表层到底层逐渐降低的变化趋势，在低氧海水中可能存在少量的细菌原位合成。海水颗粒物和表层沉积物中BHPs及相关细菌的垂直分布表明，沉积的BHPs主要来源于水体原位沉降，沉积物中原位产生并不是沉积BHPs储库的主要贡献。

     基于土壤细菌来源BHPs（腺苷-BHPs）和海洋自生来源BHPs（BHT）相对含量的陆源输入指标R_soil表明中国东部边缘海沉积有机质以MOM为主（82.70%）。BHPs可代表其生产者细菌来源的有机碳，其早期降解产物藿四醇酐也可在一定程度上指示海洋中总有机碳的降解与保存。可反映BHPs降解程度的藿四醇酐相对含量值整体较低且在低DO区域具有较低值，表明中国东部边缘海BHPs整体上降解程度较低，且低氧条件有利于BHPs和有机碳的保存。其中，海水颗粒物和表层沉积物中BHPs组分相对丰度的垂直变化表明，更稳定的BHT、BHT-isomer和2-甲基BHT在沉积物中优先保存。此外，藿四醇酐相对含量呈现离岸降低的变化趋势且在海水颗粒物中其值高于表层沉积物，这表明由近岸向外海的沉积物搬运过程中，陆源有机碳经历了较长时间的降解矿化从而更倾向于长久保存；而海洋自生来源有机碳通常具有较高活性，其在水柱沉降过程中经历了较大程度的降解转化。

2. 综合评估了BHPs特征组分作为环境代用指标指示中国东部边缘海海水低氧和碳、氮循环的适用性。发现颗粒物和沉积物中BHT-isomer及比值BHT-isomer ratio、2-甲基BHT和氨基藿四/五醇分别与水体厌氧氨氧化、溶解氧（DO）、固氮和好氧甲烷氧化（AMO）相关参数呈显著相关，这些组分可作为海洋生态环境指示指标。

  基于中国东部边缘海海水颗粒物和表层沉积物中BHPs的来源、沉降和保存过程的解析，发现携带海水环境和来源细菌信息的BHPs通常由水柱沉降输出并保存在沉积物中，具有指示海水环境变化和生物活动的重要潜能。中国东部边缘海海水颗粒物和表层沉积物中的BHT-isomer分别与海水和底层海水中厌氧氨氧化基因amx-16S rRNA丰度具有良好的响应关系和相关性，表明了BHT-isomer作为厌氧氨氧化特异性生物标志物指示海水厌氧氨氧化的可靠性和适用性。BHT-isomer与DO浓度的空间分布一致性表明，低氧条件会促进厌氧氨氧化活性，存在低DO条件的长江口和黄河口邻近海域是中国东部边缘海厌氧氨氧化脱氮的重要区域。可反映厌氧氨氧化菌相对于所有BHT来源细菌的贡献的BHT-isomer ratio，在中国东部边缘海海水颗粒物和表层沉积物中分别与海水和底层海水DO浓度具有分布一致性和显著相关性，表明了其作为海水DO的指示指标的适用性。BHT-isomer ratio与DO的综合分析表明BHT-isomer ratio阈值>0.20可用于指示海水低/缺氧环境。

  中国东部边缘海海水颗粒物和表层沉积物中的2-甲基BHT与海水中蓝细菌丰度、固氮功能基因nifH丰度和固氮速率具有良好的响应关系和相关性。这表明，尽管可能存在除固氮蓝细菌外的其他潜在来源，但中国东部边缘海中2-甲基BHT主要为固氮蓝细菌来源，其作为生物标志物指示海洋蓝细菌固氮具有一定的适用性。中国东部边缘海海水颗粒物和表层沉积物中的氨基藿四醇和氨基藿五醇总浓度，与海水中AMO功能基因pmoA丰度及底层海水、表层沉积物间隙水中溶解甲烷浓度具有良好的响应关系和相关性，表明其作为甲烷氧化标志物指示海水AMO的重要潜能与可行性。长江口和南黄海近岸海域较高的甲烷氧化标志物浓度表明该海域具有较高的AMO活性，是边缘海氧化去除甲烷的重要区域。

3. 深入探究了BHT-isomer的细菌来源及对海洋厌氧氨氧化过程和低氧的响应机制。通过控制DO条件的微观培养实验，发现培养体系内BHT-isomer为来源于海洋厌氧氨氧化菌Ca. Scalindua的BHT-x，在低氧条件下呈现最大值；BHT-x与厌氧氨氧化速率和功能基因丰度呈现显著正相关，BHT-x ratio与DO呈现显著负相关，这与外海的结论相一致，验证了BHT-x和BHT-x ratio对海洋厌氧氨氧化和低氧的响应。

  对已富集海洋厌氧氨氧化菌的表层沉积物进行控制DO条件的微观培养实验，DO梯度由低到高分别为0.30，1.32，2.71，5.10和7.79 mg/L。结果发现，培养体系内BHT-isomer为来源于海洋厌氧氨氧化菌Ca. Scalindua的BHT-x。BHT-x在培养20天和培养60天后均在次低氧条件（DO=1.32 mg/L）下呈现最高浓度，而后随DO浓度升高而降低。Ca. Scalindua是培养体系内厌氧氨氧化菌的优势属，其相对丰度在DO<5.10 mg/L时高达80%以上。培养体系内厌氧氨氧化相关功能基因amx-16S rRNA、hzsB、hzo的绝对丰度和厌氧氨氧化速率均表现出与BHT-x一致的变化趋势。BHT-x与厌氧氨氧化功能基因和厌氧氨氧化速率均呈现显著正相关，进一步验证了BHT-x对海洋厌氧氨氧化的响应。

     BHT-x相对于总BHT的比值BHT-x ratio，在培养20天和培养60天结束后均呈现出随DO浓度降低而逐渐升高的变化趋势。BHT-x ratio与海水DO浓度呈现显著的指数负相关，这与外海的调查结果相一致，验证了BHT-x ratio对海水低氧的指示，且BHT-x ratio阈值≥0.2时可用于指示海水低/缺氧条件。BHT-x及BHT-x ratio对海洋厌氧氨氧化和海水低氧的响应是由海洋厌氧氨氧化菌群落结构变化、微生物自身适应和不同溶氧浓度下的降解所共同驱动的。低氧条件下Ca. Scalindua可能通过合成更多的BHT-x膜脂来增加膜致密性，降低膜渗透性，以助于保持厌氧氨氧化所需的膜两侧质子电化学梯度。

4. 利用BHPs特征指标重建了东海内陆架南部低氧区百年来低氧和氮循环演变历程。发现百年来沉积有机质中海源贡献比例逐年增加，特别是在2000年以来富营养化增强导致MOM含量显著增加，MOM降解是低氧形成的重要原因；但在2000年之后低氧明显减弱，这可能是水体分层显著减弱的结果；低氧、厌氧氨氧化和固氮活动呈现共变现象，表明低氧促进了厌氧氨氧化，这可能在一定程度上会诱使固氮活动增强以补偿氮损失。

  东海内陆架南部低氧区沉积记录中BHPs和沉积有机质的年际变化可分为三个阶段：I（1919~1980年）、II（1980~2000年）、III（2000年后）。基于陆源输入指标R_soil的二端元混合模型估算陆源有机质（TOM）和MOM的含量及对总沉积有机质储库的贡献。结果表明，柱状沉积物中百年来沉积有机质均以MOM为主，海源贡献比例整体呈现增加趋势，特别是在2000年以来，由于富营养化的增强，MOM含量及贡献显著增加至~7 mg/g和~80%。

  东海内陆架南部低氧区沉积记录中BHT-isomer ratio的年际变化表明在第I阶段持续存在海水低氧，特别是1919~1935年和1960~1980年期间海水低氧增强；1980年后海水低氧逐渐减弱，并在1990s低氧加剧；2000年后南部浙江沿岸海域低氧明显减弱至消失。富营养化驱动的MOM降解是海水低氧形成的重要原因。尽管2000年之后沉积柱中MOM呈现增加趋势，但其低氧显著减弱至消失，这与低氧区北移的外海观测结果相一致，可能是水体分层显著减弱的结果。沉积记录中BHT-isomer和2-甲基BHT相似的年际变化表明，低氧时期厌氧氨氧化和固氮活动均增强，反之亦然。2000年之后随着低氧显著减弱至消失，厌氧氨氧化和固氮活动也随之减弱。低氧、厌氧氨氧化和固氮活动的共变化表明，低氧促进厌氧氨氧化，这可能在一定程度上会诱使固氮活动增强以补偿氮损失。

    Although shelf marginal seas account for only 8 percent of the global ocean area, they play a huge role in primary production, organic carbon burial and nitrogen budget. The Eastern China Marginal Sea is one of the important shelf marginal seas, and is also an area that is strongly exposed to land-sea interactions and human activities. In recent years, the frequent occurrence of hypoxia in the Chinese coastal sea has not only seriously damaged the marine ecological balance, but also played a role in the preservation of marine organic carbon and the removal of reactive nitrogen, which has an important impact on the marine carbon sink, nitrogen budget and even global climate change. Reconstructing the evolution of past hypoxia and carbon and nitrogen cycles is the basis for predicting future trends and formulating response strategies. As biomarkers are the main means to reflect past environmental changes, the establishment of a sensitive and reliable biomarker system is the key to accurately reconstructing the evolution of the low-oxygen, carbon and nitrogen cycles over long-time scales. Bacteriohopanepolyols (BHPs) are pentacyclic triterpenoids derived from the membrane lipids of bacterial cells, whose composition and structure are regulated by environmental conditions and cellular stress responses, and which are able to respond to and record environmental changes sensitively and stably preserved in geological carriers. Although BHPs have shown significant potential to indicate environmental changes and biological activities, there is still a lack of understanding of the origin, deposition and preservation processes of BHPs in the marine environment, and their reliability and accuracy as biomarkers remain to be explored. In this dissertation, the source, deposition and preservation processes of BHPs were analyses using seawater particles, surface sediments and columnar sediments from the Bohai Sea, Yellow Sea and East China Sea. On this basis, the reliability and applicability of BHPs as environmental proxies in the Eastern China Marginal Sea were evaluated in conjunction with the related bacterial community structure, functional genes abundance and culture experiment. The BHPs indicators were applied to the sedimentary records to reconstruct the evolution of hypoxia and nitrogen cycles in the southern hypoxic zone of the East China Sea inner shelf over the past century. The main conclusions and insights obtained are as follows:

1. The origin, deposition and preservation of BHPs in seawater particles and surface sediments in the Eastern China Marginal Sea were systematically studied. Different BHPs components were found to have typical distribution characteristics of terrestrial and marine origins. Marine-sourced bacteriohopanetetrol (BHT) and 2-Methyl BHT were mainly derived from in-situ production in the water column; Sedimentary BHPs were mainly derived from in-situ deposition in the water column; The degradation degree of BHPs as a whole was relatively low, of which BHT, BHT isomer (BHT-isomer) and 2-Methyl BHT are preferentially preserved; Sedimentary organic matter in the Eastern China Marginal Sea was dominated by marine-derived organic matter (MOM), and the low-oxygen environment is conducive to the preservation of BHPs and organic carbon.

    BHPs in seawater particles and surface sediments of the Eastern China Marginal Sea have significant source characteristics and spatial distribution features. The autochthonous marine-sourced BHT showed a changing trend of gradual increase from nearshore to offshore and from surface to bottom, and accounted for more than 60% of the bottom seawater in the offshore. The BHT-isomer consisted of BHT-34R produced by terrestrial-sourced bacteria or freshwater anaerobic ammonium oxidation (anammox) bacteria Ca. brocadia, and BHT-x uniquely produced by marine anammox bacteria Ca. scalindua. BHT-34R was present only in surface seawater within estuaries and in nearshore waters, whereas BHT-isomer in the outer waters was mainly BHT-x, which showed high values in deep hypersaline, low-oxygen seawater. Although there may be other potential bacterial sources, 2-Methyl BHT is thought to originate mainly from nitrogen-fixing cyanobacteria in surface seawater, showing an increasing trend from nearshore to offshore. Aminotetrol and aminopentol were mainly derived from aerobic methane oxidizing bacteria in surface and bottom seawater, driven by a combination of inputs from terrestrial sources and CH₄ release from sediments. Adenosyl-BHPs from terrestrial soil bacteria showed a decreasing trend from nearshore to offshore and from surface to bottom, and a small amount of in-situ bacterial synthesis may exist in low-oxygen seawater. The vertical distributions of BHPs and related bacteria in seawater particles and surface sediments indicate that sedimentary BHPs are mainly derived from in-situ deposition in the water column, and in-situ production in sediments is not a major contribution to the reservoir of sedimentary BHPs.

    The terrestrial input index R_soil based on the relative content of soil bacterial-derived BHPs (adenosyl-BHPs) and marine autochthonous-derived BHPs (BHT) indicated that sedimentary organic matter in the Eastern China Marginal Sea was dominated by MOM (82.70%). BHPs can represent the organic carbon of the bacterial origin of their producers, and their degradation products—anhydroBHT can also be indicative to some extent of total organic carbon degradation and preservation in the ocean. The values of anhydroBHT ratio, which can reflect the degree of BHPs degradation, were generally low and showed lower values low-oxygen conditions, indicating that the overall degradation degree of BHPs in the Eastern China Marginal Sea was low and the low-oxygen conditions favored the preservation of BHPs and organic carbon. Among them, the vertical changes in the relative abundance of BHP components in seawater particles and surface sediments suggest that the more stable BHT, BHT-isomer and 2-methyl BHT are preferentially preserved in surface sediments. In addition, the anhydroBHT ratio showed a trend of decreasing offshore and its values in seawater particles were higher than those in surface sediments. These evidences suggest that during the transportation of sediments from the nearshore to the open sea, terrestrial organic carbon undergoes a longer period of degradation and mineralization and is therefore more likely to be preserved for a long time; while marine autochthonous organic carbon is usually more active and undergoes a greater degree of degradation during the deposition of the water column.

2. The applicability of the characteristic components of BHPs as environmental proxies to indicate hypoxia and carbon and nitrogen cycles in seawater of the Eastern China Marginal Sea was comprehensively assessed. It was found that BHT-isomer and its ratio (BHT-isomer ratio), 2-Methyl BHT, aminotetrol and aminopentol in particulate matter and sediment were significantly correlated with the parameters related to anammox, dissolved oxygen (DO), nitrogen fixation, and aerobic methane oxidation (AMO) in the water column, respectively. Thus, these BHP components could be used as indicators of marine ecosystems.

    Based on the analysis of the source, deposition and preservation processes of BHPs in seawater particles and surface sediments from the Eastern China Marginal Sea, it was found that BHPs carrying information on seawater environment and source bacteria are usually exported from the water column by deposition and preserved in sediments, which have important potentials to indicate seawater environmental changes and biological activities. BHT-isomer in the seawater particles and surface sediments of the Eastern China Marginal Sea showed a good relationship and correlation with the abundance of amx-16S rRNA in seawater and bottom seawater, respectively. These indicate the reliability and applicability of BHT-isomer as a specific biomarker for seawater anammox. The consistency of the spatial distribution of BHT-isomer and DO concentrations indicates that low oxygen conditions promote anammox activity, and the adjacent waters of the Changjiang Estuary and the Yellow River Estuary with lower DO concentrations are important areas for anammox nitrogen loss in the Eastern China Marginal Sea. The BHT-isomer ratio, which reflects the contribution of anammox bacteria relative to all BHT-sourced bacteria, showed distributional consistency and significant correlation with seawater DO concentrations in seawater particulate matter and surface sediments of the Eastern China Marginal Sea. These suggest its applicability as an indicator of seawater DO concentrations. The comprehensive analysis of BHT-isomer ratio and DO suggests that the BHT-isomer ratio threshold > 0.20 could be used to indicate low/anoxic environment in seawater.

    2-Methyl BHT in seawater particulate matter and surface sediments of the Eastern China Marginal Sea showed a good responsive relationship and correlation with the abundance of cyanobacteria, the abundance of the nitrogen-fixing functional gene nifH, and the rate of nitrogen fixation in seawater. Despite the possible existence of potential sources other than nitrogen-fixing cyanobacteria, these further indicate the major nitrogen-fixing cyanobacterial source of 2-Methyl BHT and its applicability as a biomarker for marine cyanobacterial nitrogen fixation. The total concentrations of both aminotetrol and aminopentol in seawater particulate matter and surface sediments of the Eastern China Marginal Sea showed good response relationships and correlations with the abundance of AMO functional gene pmoA and the concentration of dissolved methane in the seawater, which suggests their important potential and feasibility as methane oxidation markers to indicate AMO in seawater. The higher concentrations of methane oxidation markers in the Changjiang Estuary and the Yellow River Estuary indicate that these areas have higher AMO activity and are important areas for methane oxidation removal in the marginal seas.

3. The bacterial origin of BHT-isomer and its response mechanism to the marine anammox and hypoxia were investigated. Through culture experiments under controlled DO conditions, it was found that the BHT-isomer in the culture system was BHT-x derived from the marine anammox bacteria Ca. Scalindua, which showed the maximum value under hypoxic conditions. BHT-x showed a significant positive correlation with anammox rate and abundance of anammox functional genes; and BHT-x ratio showed a significant negative correlation with DO, which was consistent with the findings in the ocean, validating the response of BHT-x and BHT-x ratio to marine anammox and hypoxia.

   Microculture experiments with controlled DO conditions were conducted on surface sediments that had been enriched with the marine anammox bacteria, with DO gradients from low to high of 0.30, 1.32, 2.71, 5.10, and 7.79 mg/L. The results revealed that the BHT-isomer within the culture system was BHT-x originating from the marine anammox bacteria Ca. Scalindua. BHT-x showed the highest concentration under sub-low oxygen condition (DO=1.32 mg/L) after 20 days and 60 days of incubation, and then decreased with increasing DO concentration. Ca. Scalindua was the dominant genus of anammox bacteria in the culture system, and its relative abundance was up to more than 80% at DO<5.10 mg/L. The absolute abundance and anammox rate of the functional anammox-related genes amx-16S rRNA, hzsB, and hzo within the culture system showed a consistent trend with that of BHT-x. BHT-x showed significant positive correlation with both anammox functional genes and anammox rate, further validating the response of BHT-x to marine anammox.

    The BHT-x ratio, the ratio of BHT-x relative to total BHT, showed a trend of gradual increase with decreasing DO concentration at the end of both 20 and 60 days of incubation. The BHT-x ratio showed a significant exponential negative correlation with seawater DO concentration, which was consistent with the findings in the offshore, validating the indication of BHT-x ratio on seawater hypoxia. The BHT-x ratio threshold ≥0.2 can be used to indicate seawater hypoxia/anoxia conditions. The responses of BHT-x and BHT-x ratio to marine anammox and seawater hypoxia were driven by a combination of structural changes in the marine anammox bacteria community, microbial self-adaptation, and degradation under different DO concentrations. Under hypoxic conditions, Ca. scalindua may increase membrane densification and decrease membrane permeability by synthesizing more BHT-x membrane lipids to help maintain the proton electrochemical gradient on both sides of the membrane required by anammox.

4. The evolution of hypoxia and nitrogen cycle in the southern hypoxic zone of the East China Sea shelf over the past century was reconstructed by using the characteristic indicators of BHPs. It was found that the marine-derived contribution in sedimentary organic matter increased year by year over the past century, especially since 2000, when eutrophication was enhanced, resulting in a significant increase in MOM contents. MOM degradation was an important reason for the formation of hypoxia. However, hypoxia was significantly weakened after 2000, which may be a result of the significant reduction of water column stratification. Hypoxia, anammox and nitrogen fixation activities showed co-variation, suggesting that hypoxia promotes anammox, which may induce enhanced nitrogen fixation activities to compensate for nitrogen losses to some extent.

    The interannual variations of BHPs and sedimentary organic matter in the sedimentary record of the southern hypoxic zone of the East China Sea inland shelf can be divided into three phases: I (1919-1980), II (1980-2000), and III (post-2000). A bipartite meta-mixing model based on the land-source input indicator R_soil was used to estimate the content of terrestrial organic matter (TOM) and MOM and their contributions to the total sedimentary organic matter reservoir. The results showed that the sedimentary organic matter in the column sediments was dominated by MOM over the past century, with an overall increasing trend in the proportion of contribution from sea sources. Especially since 2000, due to the enhancement of eutrophication, the content and contribution of MOM increased significantly to ~7 mg/g and ~80%.

    The interannual variation of the BHT-isomer ratio in the sedimentary record of the hypoxic zone in the southern part of the East China Sea inland shelf indicates that seawater hypoxia persisted in stage I, especially during the periods of 1919-1935 and 1960-1980, when the hypoxia increased. The hypoxia gradually weakened after 1980 and intensified in the 1990s. After 2000, the hypoxia in the southern Zhejiang coastal waters weakened significantly to disappear. The eutrophication-driven MOM degradation is an important reason for the formation of seawater hypoxia. Despite the increasing trend of MOM in the sedimentary column after 2000, its hypoxia significantly weakened to disappeared, which is consistent with the observation that the hypoxic zone shifted northward in the offshore, and may be the result of the significant weakening of the water column stratification. Similar interannual variability of BHT-isomer and 2-Methyl BHT in the sedimentary record suggests that both Anammox and nitrogen-fixing activities are enhanced during hypoxia and vice versa. Anammox and nitrogen fixation activities diminished after 2000 as hypoxia significantly diminished to disappeared. The co-variation of hypoxic conditions, anammox and nitrogen fixation activities suggests that hypoxia promotes Anammox, which may, to some extent, induce enhanced nitrogen fixation to compensate for nitrogen losses.

第1章 绪论... 1

1.1 海洋环境中的藿类生物标志物... 1

1.2 生物藿类—细菌藿多醇... 3

1.2.1 BHPs的生物合成与生理功能... 3

1.2.2 BHPs研究方法进展... 5

1.3 BHPs指示海洋碳氮循环... 8

1.3.1 BHPs指示固氮过程... 8

1.3.2 BHPs指示硝化过程... 11

1.3.3 BHPs指示厌氧氨氧化过程和海水低氧... 12

1.3.4 BHPs指示好氧甲烷氧化过程... 14

1.3.5 BHPs示踪边缘海有机质来源及迁移过程... 16

1.4 拟解决的关键科学问题... 16

1.5 本论文的研究内容... 17

第2章 研究区域及研究方法... 19

2.1 研究海域概况—中国东部边缘海... 19

2.2 外海调查站位及样品采集... 21

2.3 实验室培养实验... 22

2.4 样品分析方法... 23

2.4.1 理化参数分析... 23

2.4.2   BHPs测定分析... 25

2.4.3 DNA提取与高通量测序... 27

2.4.4 定量PCR测定... 27

2.4.5 厌氧氨氧化速率... 28

2.4.6 固氮速率... 29

2.4.7 沉积物²¹⁰Pb年代分析... 29

2.5 数据处理方法... 30

2.5.1 BHPs相关指标计算方法... 30

2.5.2 核苷酸序列登录号... 30

2.5.3 统计分析方法... 30

第3章 中国东部边缘海颗粒物/沉积物中的BHPs. 31

3.1 长江口低氧区BHPs的来源、沉降与保存... 31

3.1.1 BHPs及水文、生化参数变化特征... 31

3.1.2 颗粒物中BHPs的细菌来源及水层来源... 36

3.1.3 颗粒物沉降对沉积BHPs储库的贡献... 39

3.1.4 沉积储库中BHPs的降解与保存... 41

3.2 渤、黄、东海BHPs的分布、来源与保存... 43

3.2.1 海水颗粒物中BHPs的含量及分布特征... 43

3.2.2 表层沉积物中BHPs的含量及分布特征... 50

3.2.3 BHPs的来源判别与降解保存... 52

3.3 BHPs追踪边缘海沉积有机质来源与保存... 57

3.4 本章小结... 60

第4章 BHPs对海水低氧和碳氮循环过程的指示作用... 63

4.1 BHPs响应海水低氧环境和厌氧氨氧化过程... 63

4.2 BHPs指示固氮过程... 67

4.3 BHPs指示好养甲烷氧化过程... 70

4.4 BHPs含量和组成对DO变化的响应... 72

4.5 海洋厌氧氨氧化菌群结构和活性对DO变化的响应... 76

4.5.1 海洋厌氧氨氧化菌群结构... 76

4.5.2 海洋厌氧氨氧化菌丰度和活性... 77

4.6 BHT-x 对低氧及海洋厌氧氨氧化的响应机制... 80

4.7 本章小结... 82

第5章 基于BHPs的东海内陆架南部低氧区百年来低氧和氮循环的演变历程... 85

5.1 东海内陆架柱状沉积物中BHPs及指标的地球化学特征... 85

5.1.1 柱状沉积物年代学特征... 85

5.1.2 BHPs及其指标的年际分布特征... 86

5.1.3 有机碳及碳同位素的年际分布特征... 87

5.2 东海内陆架百年来沉积有机质来源及含量的演变过程... 88

5.2.1 东海内陆架沉积BHPs和有机质的来源... 88

5.2.2 东海内陆架百年来陆源和海源有机质含量的演变过程... 90

5.3 东海内陆架南部低氧区百年来低氧演变历程及驱动机制... 91

5.4 东海内陆架南部低氧区百年来氮循环演变历史... 93

5.5 本章小结... 94

第6章 结论与展望... 95

6.1 论文主要结论... 95

6.2 论文创新与特色... 97

6.3 问题与展望... 97

参考文献... 99

致谢... 115

作者简历及攻读学位期间发表的学术论文与其他相关学术成果 ... 117