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1.
海洋沉积物中色素生物标志物研究进展   总被引：1，自引：0，他引：1  
海洋沉积物中的光合色素包含着水体、沉积物中浮游和底栖植物以及微生物群落的丰富信息,能表征特定生物来源,在埋藏到沉积物甚至发生某些改变之后仍然保留其源信息,是一类重要的化学生物标志物.结合总有机碳、总氮等其他海洋地球化学参数,沉积色素可用来研究海洋浮游植物和光合细菌的群落组成和丰度,反演海洋初级生产、水体富营养化水平及其历史趋势,指示水体和沉积物氧化还原条件,揭示海域气候条件等现状及其历史变化.沉积色素的研究,对于掌握海洋中碳的生物地球化学循环过程,回溯古环境、古海洋、古生态以及古气候记录,制定合理的海洋管理政策具有十分重要的意义.阐述了沉积物中色素的分类、来源、性质和分析方法,分析了色素在沉积物中的保存和变化规律,探讨总结了沉积色素作为化学生物标志物在海洋学研究中的应用.  相似文献   

2.
文章选择青藏高原腹地可可西里边缘地区古湖泊为研究对象,通过对湖泊沉积物有机碳、氮和粒度等分析,对中更新世以来BDQ06孔湖泊沉积物有机碳同位素的波动特征及其影响因素进行了分析。结果表明:湖泊沉积物有机质以湖泊自生植物为主,有机碳同位素的大小主要指示挺水植物与沉水植物的比例,进而指示湖泊水体大小的变化。沉积物C/N值较低时;碳同位素偏重阶段,湖泊沉积物以沉水植物为主,植物主要利用水中溶解的CO2进行光合作用,因此有机碳同位素偏正,指示湖泊水体较大,环境条件较好;碳同位素偏负阶段,湖泊沉积物以挺水植物和浮游生物为主,植物主要利用大气中CO2作为碳源,类似于C3植物,碳同位素偏轻,指示湖泊水体较小,气候偏干。其中在岩芯的部分层位有机碳δ13C曲线出现几个明显偏低的位置,对应的C/N>10,说明此时段有大量陆源高等植物进入湖泊,并不是由挺水植物和浮游植物所造成的。  相似文献   

3.
作为一类天然色素,类胡萝卜素在自然界中广泛分布。在沉积记录中,类胡萝卜素多以结构稳定的衍生物形式赋存。部分具有芳香基的结构的组分与光合硫细菌的活动有关,因而这些特定生物来源的组分为恢复古水体环境提供了一个重要的依据。通常光合硫细菌多生存在缺氧且富硫的透光层,地质记录中的芳香基类胡萝卜素往往反映了古水体中发育硫化透光带。类胡萝卜素衍生物的组合差异与硫细菌群落的相关性为古水深、微生物优势群落以及营养元素利用与循环等方面的研究提供了线索和证据。因此,类胡萝卜素衍生物在油源对比、生命起源、生物灭绝事件以及大洋缺氧事件等诸多地质过程的研究中起到至关重要的指示作用。本文主要通过探讨准噶尔盆地南缘安集海河组有机质中的类胡萝卜素的结构,分析其成因类型和特定来源,阐释古环境与古气候演化,进而恢复与重建渐新世时期准噶尔盆地南缘古湖泊的水体条件与微生物群落。从结果来看,准噶尔盆地安集海组中发育绿硫细菌来源的绿硫菌烷、异海绵烷等芳香基类胡萝卜素,可以推测这一时期湖泊水体存在硫化透光带现象;同时以叶黄素为来源的叶黄烷指示了蓝细菌是古湖泊中生物群落的重要组成部分。古湖泊发育硫化透光带往往与水体分层有关,而准噶尔盆地渐新世晚期的古气候由湿润转变为干旱似乎对湖泊盐度分层提供有利条件。与此同时,绿硫细菌中出现较高含量的棕色绿硫细菌菌株反映了安集海河组古湖泊的水深较深,且分布范围广阔。通过对安集海河组类胡萝卜素研究,认为渐新世时期准噶尔盆地南缘原始湖泊分布范围向南延伸较广,与构造研究结果吻合。  相似文献   

4.
海洋环境中的厌氧铵氧化过程作为实现固定态氮从海洋生态系统中移除的一个新途径,广泛地存在于各种海洋环境中,包括永久性缺氧水体、沉积物、海冰甚至海底热液,是海洋氮循环过程中一个非常重要的环节。开展海洋环境中厌氧铵氧化过程的研究可以更好地量化海洋氮循环过程中的收支,而这一收支在很大程度上影响着全球的气候变化。介绍了海洋环境中厌氧铵氧化过程研究历史,并分别讨论了在大洋缺氧水体和沉积物中厌氧铵氧化速率的分布情况,同时还总结了海洋环境因子如温度、氧气、硫化氢、NO3-/NO2-、NH4+以及有机物等对厌氧铵氧化的影响。最后探讨了该领域研究中所存在的问题并指出了亟待开展的工作:特定大洋缺氧水体中厌氧铵氧化与反硝化的争议以及近岸缺氧水体中厌氧铵氧化的研究;陆架及深海大洋沉积物中厌氧铵氧化的深入研究;对于全球海洋氮循环收支的重新评估。  相似文献   

5.
硅藻广泛分布于湖泊沉积物中,其硅质骨骼的硅氧同位素组成(δ18O和δ30Si)通常可以记录当时水体的温度和同位素组成.近十年来,湖泊沉积物硅藻氧同位素组成(δ18Odia tom)被广泛用于指示湖区温度变化和水体氧同位素组成的变化.然而,迄今尚未见有对湖泊沉积物硅藻硅同位素的系统研究的报道.  相似文献   

6.
沉积物微量金属元素在重建水体环境变化中的意义   总被引：7，自引：0，他引：7  
沉积物所记录的微量金属含量与形态的变化是指示人类活动影响下水体环境变化的有效指标,主要用于指示沉积物重金属污染、水体初级生产力变化和氧化还原条件等方面的水体环境状况。总体而言,沉积物中微量金属含量在近一个世纪以来显著上升,反映了采矿、冶金、污水排放、化肥使用、煤炭和石油燃烧等各种人类活动造成水体和沉积物重金属污染的记录作为浮游植物微量营养元素,Cu、Zn、Ni、Ba、Cd等在沉积物中的记录可以指示水体初级生产力水平。U、Mo、V、Cu、Cd、Mn等氧化还原敏感元素在沉积物中的富集或贫化,及其比值(如Re/Mo、Cd/U、Th/U和V/Sc)的变化,是指示水体和沉积物氧化还原环境的有效指标。但需要指出的是,在受人类活动影响的水体中,这些生产力和氧化还原指标很少能指示水体生产力或氧化还原状况,可能主要与人类活动同时造成这些金属元素大量污染输入而掩盖了其自生来源和内在变化的沉积记录有关。所以,对沉积物中微量金属元素来源的判别(陆源碎屑输入、人为输入和水体自生来源)是重建水体环境变化的重要前提。本文总结了多种化学和统计学方法(包括同位素示踪法、化学提取法、富集因子法和主成分分析法等)在沉积物金属来源判别中的应用另外,成岩作用等多种因素会干扰沉积物金属记录对环境变化的指示作用,所以构建多元素指标来综合判断沉积物记录所反映的环境信息是今后的研究所必须关注的  相似文献   

7.
细菌藿多醇（Bacteriohopanepolyols，BHPs）是细菌细胞膜中高度结构变异的五环三萜类化合物，易保存且受成岩作用影响较小，广泛分布于陆地和海洋环境中。BHPs作为一种新型微生物标志物，由于其细菌来源专属性和环境专属性，近年来已在示踪有机质来源、环境演变过程以及反演古环境方面表现出巨大的应用潜力。本文系统分析了近年来全球土壤、沉积物和海水中BHPs的组成、分布和来源，发现热带和温带区域中BHPs的多样性和含量通常高于寒带区域，且由土壤、河流、近海到外海海域逐渐降低。探讨了土壤标志物BHPs、细菌霍四醇同分异构体（BHT- Ⅱ）和35- 氨基霍多醇在有机质来源、缺氧环境、厌氧氨氧化和甲烷氧化活动方面的环境指示作用及在海洋生态环境重建中的应用，以期为示踪海洋生态环境变化提供新指标和新途径。  相似文献   

8.
在湖泊沉积的古气候研究中,沉积物粒度的气候指示意义常被解释为,粗粒沉积物指示低水位时期的干旱气候,而细粒沉积物则反映高水位时期的湿润气候。通过对江汉平原江陵剖面湖泊沉积物多环境指标的综合对比及相互印证,揭示出湖泊沉积物粒度的另一种气候解释,粗粒沉积物指示降水量较大的湿润气候,而细粒沉积物则对应降水量相对较少的干旱气候。由于湖泊沉积环境的复杂性,湖泊沉积物的粒度指标存在多解性,因此,在利用粒度组成判别气候环境的演化时,必须考虑湖泊自身的环境因素,同时结合其它指标来综合判识。  相似文献   

9.
马奎  肖南  蒲钰龙  钟佳倚 《中国地质》2021,48(1):309-321
为探讨华北地区中元古界洪水庄组黑色泥页岩物源和沉积环境,采集了燕辽地区清河剖面洪水庄组样品,进行元素地球化学测试和分析。结果表明:洪水庄组沉积物来源不仅有陆源碎屑物质,还有海水沉积物贡献。Y/Ho和ΣREE交会图版分析认为海水沉积物来源占比为10%~20%。此外,稀土元素分布模式以及Ce和Eu异常表明沉积物来源有火山热液活动的参与。Mo-EF/U-EF分析结果表明洪水庄为海洋非滞留海盆沉积环境,氧化还原条件在沉积期发生了演变:在洪一段沉积时期,水体还原程度强,为厌氧-硫化环境;洪二段沉积时期,水体还原程度降低,为贫氧-厌氧环境。分析认为洪水庄组物源组成和沉积环境演变与沉积构造背景密切相关。  相似文献   

10.
沉积物中磷的赋存形态及磷形态顺序提取分析方法   总被引：11，自引：1，他引：10  
阐述了当前我国水体富营养化的现状,水体的富营养化与水体中磷、氮的浓度以及二者的浓度比值有着密切的关系。水体富营养化时氮和磷的浓度均很高,但没有一个固定的值,是在一个较宽泛的富营养范围内,氮和磷的浓度比值大多在10∶1～20∶1。湖泊沉积物作为湖泊水体中磷的重要蓄积库,是湖泊流域磷循环的重要归属,也是湖泊水体内源性磷的主要来源,沉积物中极少量的稳定磷转化为活性磷就会造成湖泊水体富营养化。文中介绍了沉积物中无机磷形态的分类,评述了欧盟标准局在研制湖泊沉积物磷形态标准物质时比对采用的4种提取方法(Willimas法、Hieltjes-Lijklema法、Ruttenberg法、Golterman法),总结了国内外学者所应用的沉积物中磷的各种形态提取方法和磷各形态的分析测定方法,国内学者应用的方法是在国外学者方法的基础上提出的,阐述了顺序提取方法及其地球化学意义。简要评述了湖泊沉积物中磷的生物释放、物理释放和化学释放三种释放机制,这三种释放机制相辅相成,在一特定的环境条件下某一过程可能占主导地位来控制沉积物磷的释放。最后提出应该加强对沉积物中磷的各种形态的专属提取剂及其提取有效性的分子表征和检测,更加细化对于沉积物中磷形态的分类和创新各种磷形态的分析方法,建立沉积物-水体磷的迁移、循环和转化模型,这对于从根本上解决富营养化问题具有重要意义。  相似文献   

11.
The molecular diversity of the purple photosynthetic bacteria was assessed during temporal pigmentation changes in four interconnected wastewater stabilization ponds treating domestic wastewater by denaturant gel gradient electrophoresis method applying pufM gene. Results revealed high phylogenetic diversity of the purple phototrophic anoxygenic bacteria community characterized by the presence of the purple non-sulfur, purple sulfur, and purple aerobic photosynthetic anoxygenic bacteria. This phototrophic bacterial assemblage was dominated by the purple non-sulfur bacteria group (59.3 %) with six different genera followed by the purple sulfur community (27.8 %) with four genera and finally 12.9 % of the pufM gene sequences were assigned throughout the aerobic anoxygenic phototrophic bacterial group. The purple phototrophic bacterial community was characterized by the presence of salt-dependant bacterial species belonging to the genus Marichromatium, Thiorhodococcus, Erythrobacter, and Roseobacter. The wastewater treatment plant performances were unsatisfactory, and the biological and chemical parameters suggested that the purple photosynthetic bloom was correlated with the eutrophic state.  相似文献   

12.
The productivity of anoxygenic phototrophic bacteria (APB) can be inferred in the sediments of Qinghai Lake from the changing abundance of bacteriophaeophytin a (Bph-a). Using diffuse reflectance spectroscopy (DRS), we identified Bph-a in Qinghai Lake sediments from the late glacial period through the Holocene with a resolution of one sample every 30–50 years. The Bph-a profile of Qinghai Lake demonstrates that in the last 18,000 years APB were only present between 4.2 and 14 ka BP, a period of high rainfall and high summer solar insolation. All the APB blooming events correspond to times of enhanced freshwater influx as revealed by percent redness, an indicator of the input of iron oxide minerals. Our data suggest that solar insolation sets the stage for APB blooms, which are then promoted by increased summer monsoon rainfall and nutrients resulting in the development of a chemocline in the lake. The blooming of APB in Qinghai Lake appears as discrete centennial-scale APB events likely linked to solar activities. Our results suggest the presence of solar-induced, century-long, intense summer monsoon episodes in the middle and early Holocene and the late glacial period.  相似文献   

13.
A variety of mechanisms have been proposed to explain how light and dark couplets are formed in the profundal sediments of meromictic lakes but none of these explanations acknowledges the significance of the sudden and massive mortality of mixolimnetic anaerobic bacteria. Data collected from sedimentation chambers suspended below the chemocline in a small meromictic lake indicate that a massive mortality of photosynthetic bacteria was induced by a sudden intrusion of partially oxygenated water into the anaerobic lower mixolimnion. The resulting deposition of anaerobic bacteria (0.45 mg dry wt cm?2 day?1) contributed 60% of the annual sediment influx during a 14-day period. It is postulated that the sudden sedimentation of the anaerobic bacteria inhabiting the lower mixolimnion of some meromictic lakes contributed to the formation of the dark-colored laminae in the sediments of these lakes.  相似文献   

14.
Bitumens extracted from 2.7 to 2.5 billion-year-old (Ga) shales of the Fortescue and Hamersley Groups in the Pilbara Craton, Western Australia, contain traces of molecular fossils. Based on a combination of molecular characteristics typical of many Precambrian bitumens, their consistently and unusually high thermal maturities, and their widespread distribution throughout the Hamersley Basin, the bitumens can be characterized as ‘probably of Archean age’. Accepting this interpretation, the biomarkers open a new window on Archean biodiversity. The presence of hopanes in the Archean rocks confirms the antiquity of the domain Bacteria, and high relative concentrations of 2α-methylhopanes indicate that cyanobacteria were important primary producers. Oxygenic photosynthesis therefore evolved > 2.7 Ga ago, and well before independent evidence suggests significant levels of oxygen accumulated in the atmosphere. Moreover, the abundance of cyanobacterial biomarkers in shales interbedded with oxide-facies banded iron formations (BIF) indicates that although some Archean BIF might have been formed by abiotic photochemical processes or anoxygenic phototrophic bacteria, those in the Hamersley Group formed as a direct consequence of biological oxygen production. Biomarkers of the 3β-methylhopane series suggest that microaerophilic heterotrophic bacteria, probably methanotrophs or methylotrophs, were active in late Archean environments. The presence of steranes in a wide range of structures with relative abundances like those from late Paleoproterozoic to Phanerozoic sediments is convincing evidence for the existence of eukaryotes in the late Archean, 900 Ma before visible fossil evidence indicates that the lineage arose. Sterol biosynthesis in extant eukaryotes requires molecular oxygen. The presence of steranes together with biomarkers of oxygenic photosynthetic cyanobacteria suggests that the concentration of dissolved oxygen in some regions of the upper water column was equivalent to at least ∼1% of the present atmospheric level (PAL) and may have been sufficient to support aerobic respiration.  相似文献   

15.
MIKE DICKMAN 《Sedimentology》1985,32(1):109-118
In a small meromictic lake near Toronto, Canada, a mass mortality of photosynthetic bacteria followed the ventilation of the chemocline during fall (autumn) and resulted in 3–8 g m-2 day-1 of organic matter being deposited as a dark layer in sediment traps which were suspended in the permanently anaerobic zone. This mass mortality of photosynthetic bacteria occurred in late autumn following the annual thermal destratification of the lake's mixolimnion. Wind mixing during this period of homeothermy resulted in the introduction of low levels of dissolved oxygen into the lake's chemocline. The ensuing mass mortality of photosynthetic bacteria resulted in the release of elemental sulphur as the sulphur-rich bacteria decomposed and sank to the bottom of the lake. The ferrous ions in the water below a depth of 15 m in Crawford Lake reacted with this sulphur to form black ferrous sulphides and pyrite which formed a dark microlamina on the lake floor. Each dark microlamina was overlain by a light coloured (calcite-rich) layer which was deposited each spring and summer during the 3 yr period of this study. The mechanism of microlamina formation elucidated here has been based on the examination of bi-weekly sediment trap information. This approach has permitted an explanation of the mechanisms by which specific events such as calcite precipitation and phytoplankton seasonal succession are transcribed into the sediment record.  相似文献   

16.
The comparison of the fatty acids between aerobic anoxygenic phototrophic bacteria (AAPB) and their phylogenetic relatives has been a fascinating but yet enigmatic topic, enhancing our understanding of physiological variations between these evolutionarily related microorganisms. Two strains of marine bacteria, both phylogenetically falling into Erythrobacter sp., were isolated from the South China Sea, and demonstrated, respectively, to be an aerobic anoxygenic phototrophic bacteria (AAPB) (JL475) which is capable of anoxygenic photosynthesis via BChl a, and an obligate heterotroph (JL316) with a lack of BChl a, on the basis of phylogenetic analysis and pure culture cultivation. Phospholipid fatty acids (PLFA) and glycolipid fatty acids (GLFA) of the two strains were extracted and analyzed by gas chromatographymass spectrometry. The PLFA in JL475 AAPB are characterized by C18:1 C18:2ω7,13 and C18:1, with the C18:2ω7,13 being a specific compound for AAPB and in particular for Erythrobacter longus and some of its phylogenetically closely related relatives. The JL316 strain is characterized in PLFA by the presence of C18:1, C16:1 and C16:0, and in particular C17:1. GLFA do not show any discrimination between the two strains. Four α,ω-dicarboxylic acids, including 1,8-octanedioic acid, 1,9-nonanedioic acid, 1,10-decanedioic acid and 1,11-undecanedioic acid, are present only in JL316 GLFA, presumably derived from metabolic products. C14-C16 2-hydroxy fatty acids were found in the two strains, probably assuming a similar function of their LPS in outer membranes.  相似文献   

17.
The accumulation of organic matter (OM) during oceanic anoxic events (OAEs) that took place in the Mesozoic may reflect different biogeochemical pathways and feedbacks related to palaeoenvironmental changes. It originates from a combination of nutrient cycling, metal concentrations and position of the chemocline and/or pycnocline controlling biological production. Because ocean stagnation cannot induce euxinia, an expanded oxygen minimum zone (OMZ) associated with upwelling and improved hydrological cycles is more commonly accepted. In some depositional settings, it permitted the evolution of anoxia/dysoxia to euxinia (sulphidic waters). The latter is recorded by the presence of anoxygenic phototrophs and involved denitrification, anaerobic oxidation of methane and sulphate reduction. In order to better constrain different OAE palaeoenvironments, models are suggested here that show the evolution from main microbial communities thriving through the water column to bacterial and more complex microbial mats. Therefore, microbial processes have a key role in OM production and metabolization. They directly influence the position of the chemocline. Detailed study of the OM preserved in black shales will be key to understanding OAEs.  相似文献   

18.
The latest Permian was a time of major change in ocean chemistry, accompanying the greatest mass extinction of the Phanerozoic. To examine the nature of these changes, samples from two well-studied marine sections that span the Permian-Triassic boundary have been analyzed: the Meishan and Shangsi sections located in Southern China. Isotopic analysis of the carbonate-associated sulfate in these samples provides a detailed record of several isotopic shifts in δ34SCAS approaching and across the PTB, ranging from +30 to −15‰ (VCDT), with repeated asynchronous fluctuations at the two locations. We interpret the patterns of isotopic shifts, in conjunction with other data, to indicate a shallow unstable chemocline overlying euxinic deep-water which periodically upwelled into the photic zone. These chemocline upward excursion events introduced sulfide to the photic zone stimulating a bloom of phototrophic sulfur oxidizing bacteria. We hypothesize that elemental sulfur globules produced by these organisms and 34S-depleted pyrite produced in the euxinic water column were deposited in the sediment; later oxidation led to incorporation as CAS. This created the large changes to the δ34SCAS observed in the latest Permian at these locations.  相似文献   

19.
Lagunillo del Tejo is a small doline lake in a karstic region of the Iberian Ranges (central-eastern Spain) that undergoes significant lake level fluctuation in response to changing aquifer influxes. In order to assess changes in the primary producer community in the lake over the last two centuries and to elucidate whether these were conditioned by climatic variability, photosynthetic pigments and their derivatives were extracted from the sediments and the data analysed using multivariate statistical techniques. Quantitative variations in total pigment concentrations through the sedimentary sequence are considered a result of changes in sedimentation rate, largely due to lake level fluctuation. Rapid lowering of the level results in an increase in detritic mineral matter eroded from the sides of the lake, which accumulates in the sediment and dilutes the organic matter content in the corresponding sediment layers. On the other hand, shifts in the relative abundances of the different pigments suggest the development of two different primary producer communities: (i) planktonic, comprising cyanobacteria, chlorophytes, cryptophytes and purple sulfur bacteria and (ii) primary producers related to the littoral environment, mostly submerged macrophytes. These two communities showed alternating relative importance over the last two centuries, as a biotic response to lake level fluctuation during wet and dry periods, respectively.  相似文献   

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