Microbial ecology of the stratified water column of the Black Sea as revealed by a comprehensive biomarker study

The stratified water column of the Black Sea is partitioned into oxic, suboxic, and euxinic zones, each characterized by different biogeochemical processes and by distinct microbial communities. In 2003, we collected particulate matter by large volume in situ filtration at the highest resolution to date for lipid biomarker analysis and bacterioplankton for enumeration of major prokaryotic groups. Abundances of several prokaryotic groups were estimated using CARD-FISH probes specific for Bacteria, Archaea (Crenarchaeota and Euryarchaeota), epsilonproteobacteria (mainly sulfide oxidizers) and sulfate reducing bacteria. We also measured a wide range of bacterial and archaeal lipid biomarkers. Depth distributions of diagnostic biomarkers are matched with zonation of microbial processes, including aerobic bacterial oxidation of methane, oxidation of ammonium by bacteria and archaea, metal reduction, and sulfide oxidation at the chemocline, and bacterial sulfate reduction and anaerobic oxidation of methane by archaea in the anoxic zone. Cell densities for archaea and sulfate reducing bacteria are estimated based on water column biomarker concentrations and compared with CARD-FISH results.     

Anaerobic oxidation of methane (AOM) in marine sediments from the Skagerrak (Denmark): I. Geochemical and microbiological analyses

The organic rich sediments of the Skagerrak contain high quantities of shallow gas of mostly biogenic origin that is transported to the sediment surface by diffusion. The sulfate methane transition zone (SMTZ), where anaerobic oxidation of methane (AOM) and sulfate reduction occur, functions as a methane barrier for this upward diffusing methane.To investigate the regulation of AOM and sulfate reduction rates (SRR) and the controls on the efficiency of methane consumption, pore water concentrations, and microbial rates of AOM, sulfate reduction and methanogenesis were determined in three gravity cores collected along the slope of the Norwegian Trench in the Skagerrak. SRR occurred in two distinct peaks, at the sediment surface and the SMTZ, the latter often exceeding the peak AOM rates that occurred at the bottom of the SMTZ. Highest rates of both AOM and SRR were observed in a core from a pockmark, where advective methane transport occurred, generating high methane and sulfate fluxes. But even at this site with a shallow SMTZ, the entire flux of methane was oxidized below the sediment surface. AOM, SRR and methanogenesis seem to be closely associated and strongly regulated by sulfate concentrations, which were, in turn, regulated by the methane flux. Rate measurements of SRR, AOM and methanogenesis revealed a tight coupling of these processes. Bicarbonate-based methanogenesis occurred at moderate sulfate concentrations (>5 mM) above the AOM zone but seemed to be inhibited in the depth where AOM occurred. The unbalanced stoichiometry of AOM and SRR in the SMTZ was more pronounced in rate measurements than in methane and sulfate fluxes, and seemed more likely be related to enhanced SRR in this zone than an underestimation of methane fluxes.     

Energy sources for diagenesis: Evidence from the Black Sea

Complex investigations of recent and Drevnechernomorian (ancient Black Sea) sediments from the outer shelf, continental slope, and deep-water basin of the Russian Black Sea sector have been carried out using samples collected during cruise of the R/V Professor Shtokman organized by the Institute of Oceanology of the Russian Academy of Sciences (March 2009) and expedition of “YUZHMORGEO” (summer 2006). Rates of the main anaerobic processes during diagenesis (sulfate reduction, dark CO₂ fixation, methanogenesis, and methane oxidation) were studied for the first time in sediment cores of the studied area. Two peaks in the rate of microbial processes and two sources of these processes were identified: the upper peak near the water-sediment contact is related to the solar energy (OM substrate of the water column) and the lower peak at the base of the Drevnechernomorian sediments with high(>1000 μM) methane concentration related to the energy of anaerobic methane oxidation. The neogenic labile OM formed during this process is utilized by other groups of microorganisms. According to experimental data, the daily rate of anaerobic methane oxidation is many times higher than that of methanogenesis, which unambiguously indicates the migration nature of the main part of methane.     

Geochemistry at the sulfate reduction-methanogenesis transition zone in an anoxic aquifer—A partial equilibrium interpretation using 2D reactive transport modeling

The study addresses a 10 m deep phreatic postglacial sandy aquifer of vertically varying lithology and horizontally varying infiltration water chemistry, displaying calcite dissolution, ion-exchange, and anaerobic redox processes. The simple variations in lithology and infiltration combine into a complex groundwater chemistry, showing ongoing Fe-oxide reduction, sulfate reduction and methanogenesis. Rates of sulfate reduction, methanogenesis and methane oxidation were measured directly using radiotracers. Maximum rates were 1.5 mM/yr for sulfate reduction, 0.3 mM/yr for methanogenesis, and only 4.5 μM/yr for methane oxidation. The overlap of sulfate reduction and methanogenesis was very small. The important intermediates formed during the degradation of the organic matter in the sediment, formate and acetate, had concentrations around 2 μM in the sulfate reducing zone, increasing to 10 and 25 μM in the methanogenic part. The concentration of H₂ was around 0.25 nM in the Fe-reducing zone, 0.4 nM in the sulfate reducing zone, and increased to 6 nM in the methanogenic zone. Using in situ concentrations of products and reactants the available energies for a range of different reactions could be calculated. The results of the calculations are in accordance with the observed distribution of the ongoing redox processes, implying that the system is well described using a partial equilibrium approach. A 2D numerical PHAST model of the system based on the partial equilibrium approach, extended by implementing specific energy yields for the microbial redox processes, could explain most of the observed groundwater geochemistry as an expression of a closely coupled system of mineral equilibria and redox processes occurring at partial equilibrium.     

Biogeochemical processes of carbon and sulfur cycles in sediments of the outer shelf of the Black Sea (Russian Sector)

Within the mass of recent (unit-I) and ancient Black Sea (unit-II) sediments on the outer shelf of the Russian sector of the Black Sea, the rates of anoxic processes participating in diagenetic transformations of carbon and sulfur compounds were first measured using ³⁵S and ¹⁴C radioactive tracers. The main energy source for biogeochemical processes in (unit-I) sediments is the organic matter (OM) supplied to the bottom from the water mass. In (unit-II) sediments, this is methane in a migratory form proved by the excess of its oxidation rate over that of its generation. In recent silt, the primary microbial process is sulfate reduction; in unit-II, this is methane anoxic oxidation by the consortium of archeides and sulfate reductants. The organic matter produced in methane oxidation, in turn, acts as an energy source for the community of anaerobic heterotrophic microorganisms in the bottom sediments, which are remote from the water-sediment interface.     

Anaerobic oxidation of methane (AOM) in marine sediments from the Skagerrak (Denmark): II. Reaction-transport modeling

A steady-state reaction-transport model is applied to sediments retrieved by gravity core from two stations (S10 and S13) in the Skagerrak to determine the main kinetic and thermodynamic controls on anaerobic oxidation of methane (AOM). The model considers an extended biomass-implicit reaction network for organic carbon degradation, which includes extracellular hydrolysis of macromolecular organic matter, fermentation, sulfate reduction, methanogenesis, AOM, acetogenesis and acetotrophy. Catabolic reaction rates are determined using a modified Monod rate expression that explicitly accounts for limitation by the in situ catabolic energy yields. The fraction of total sulfate reduction due to AOM in the sulfate-methane transition zone (SMTZ) at each site is calculated. The model provides an explanation for the methane tailing phenomenon which is observed here and in other marine sediments, whereby methane diffuses up from the SMTZ to the top of the core without being consumed. The tailing is due to bioenergetic limitation of AOM in the sulfate reduction zone, because the methane concentration is too low to engender favorable thermodynamic drive. AOM is also bioenergetically inhibited below the SMTZ at both sites because of high hydrogen concentrations (∼3-6 nM). The model results imply there is no straightforward relationship between pore water concentrations and the minimum catabolic energy needed to support life because of the highly coupled nature of the reaction network. Best model fits are obtained with a minimum energy for AOM of ∼11 kJ mol⁻¹, which is within the range reported in the literature for anaerobic processes.     

综合大洋钻探计划311航次沉积物中自生黄铁矿及其硫稳定同位素研究

对综合大洋钻探计划(IODP)311航次652个岩心沉积物样品进行了自生黄铁矿颗粒筛选、显微形貌特征及其硫稳定同位素组成等初步研究。扫描电镜(SEM)照片显示黄铁矿以微球粒状和立方体状形貌产出,其成因与微生物作用和无机作用有关。黄铁矿的δ34SCDT值变化范围较大,从-35.4‰到+53.6‰,其成因与甲烷厌氧氧化作用(AOM)的关系密切。海水源为主的硫酸盐参与了沉积物上部的AOM过程,黄铁矿硫稳定同位素正偏的原因可能与较强的AOM作用和较多的残余硫酸盐参与有关。冷泉背景站位中黄铁矿的δ34SCDT值随着深度增加而增加,从浅表层的-35.83‰增加到深处的32.49‰,反映深处沉积物内黄铁矿形成过程中曾有过较多的残余硫酸盐参与还原,暗示其背景曾经是更高的甲烷通量和更强的AOM作用。研究结果提供了现代海洋天然气水合物背景下沉积物中自生黄铁矿及其硫稳定同位素特征记录,对于寻找我国海域天然气水合物资源,探索地史时期古海洋沉积物中甲烷事件记录具有重要的意义。     

华北地台串岭沟组砂脉中自生碳酸盐沉淀和自生黄铁矿——中元古代甲烷厌氧氧化的沉积证据

华北中元古界串岭沟组暗色页岩中普遍发育的砂脉构造被解释为气体逃逸形成的沉积构造。在砂脉和相邻围岩中发现有自生碳酸盐沉淀和自生黄铁矿。自生碳酸盐主要由白云石组成,表现为微晶质条带或隐晶质斑块状胶结物。微晶白云石条带多出现在有机质纹层密集发育的部位,沿微生物膜两侧发育;而隐晶质斑块多以胶结物形式充填粒间孔隙或沿砂脉外缘密集产出。围岩中共生草莓状黄铁矿,砂脉中有具环带黄铁矿。这种特殊的矿物组构以及富有机质沉积和丰富的微生物成因构造(MISS)均表明串岭沟组形成于缺氧环境。层面发育的气泡构造为砂脉的气体逃逸成因提供了支持,而自生碳酸盐和黄铁矿则是沉积浅层硫酸盐-甲烷转换带(SMTZ)甲烷厌氧氧化(AOM)和细菌硫酸盐还原(BSR)的产物;气体源于有机质的厌氧分解和甲烷菌活动。砂脉中发现有疑似微生物化石,围岩含古菌和硫细菌生物标志物,表明有发生AOM和BSR作用的条件。串岭沟组砂脉中识别的自生碳酸盐沉淀及其AOM成因对进一步认识中元古代古海洋与古气候条件具有重要意义。由于海洋的低硫酸盐浓度,SMTZ带很浅,海底沉积层的甲烷仅少量被AOM消耗;而大量甲烷进入大气必然导致中元古代强烈的温室气候效应。     

华北地台中元古代碳酸盐岩中的微生物成因构造及其生烃潜力

华北地台中元古界主要由环潮坪石英砂岩、浅海碳酸盐岩和浅海—泻湖相暗色页岩3种沉积相组合构成,以陆表海浅水碳酸盐岩占主导。碳酸盐岩中除含有丰富的微古植物、宏观藻类和微生物建隆外,还发育大量的微生物成因构造(MISS)和微生物诱发的碳酸盐沉淀(MMCP)。微生物席和MISS构造在高于庄组上部(约1.6 Ga)和雾迷山组下部(约1.45 Ga)碳酸盐岩中尤为发育,表明活跃的微生物活动和高有机质产量。在石化微生物席中,发现有丝状、球状细菌化石和草莓状黄铁矿;围岩中发现有针状文石、花瓣状重晶石、放射状菱铁矿、铁白云石和葡萄状碳酸盐胶结物等多种自生碳酸盐矿物,指示甲烷厌氧氧化(AOM)导致的自生碳酸盐沉淀。中元古代的温暖气候和海洋分层、缺氧、硫化条件有利于微生物的高生产量和高有机质埋藏率。气隆构造和核形石状碳酸盐结核反映浅埋藏条件下活跃的成烷作用和甲烷排放,围岩和MMCP中富沥青质。华北地台中元古界富微生物席碳酸盐岩有良好的生烃潜力,有可能形成重要的烃源岩。据微生物席、MISS构造及MMCP的研究,初步估算华北地台中元古代碳酸盐岩的概略生烃潜力约为10×108t石油当量。     

白云岩有机成因模式:机制、进展与意义

白云岩是一种常见的碳酸盐岩,它广泛分布在古代碳酸盐岩台地中,却很少见于全新世沉积物中,这构成了一个未解之谜。近20多年的研究成果表明,早期成岩过程中微生物参与的硫酸盐还原反应、甲烷生成和厌氧氧化反应以及有氧呼吸作用能够促进白云石的沉淀:细菌细胞和胞外聚合物(EPS)带有负电荷,能够聚集溶液中Mg2+和Ca2+;同时上述氧化还原反应产生HCO3-,提高了孔隙水中反应物的浓度;这样在细菌细胞周围形成一个对白云石超饱和的微环境,有利于白云石的沉淀。这是一种新的白云石成因模式,微生物活动和有机质是影响白云石形成最重要的因素,特殊的球状形态和碳同位素特征是鉴别有机成因白云石的重要标志。白云岩有机成因模式为认识地质历史时期大套白云岩的成因、探索"白云岩之谜"提供了新的思路。     

我国北西部地区层间氧化带砂岩型铀矿床微生物与铀成矿作用研究初探

层间氧化带砂岩型铀矿床中微生物参与成矿现象和微生物活动证据越来越多,表明微生物对当今我国主攻的层间氧化带砂岩型铀矿床的形成起重要作用。本文利用分子生物学、活菌培养和实验室模拟等方法对新疆十红滩和蒙其古尔两个典型砂岩型铀矿床中微生物与铀成矿作用关系进行了探讨,结果表明不同地球化学环境带岩石中主要微生物类群的分布特征不同,表现出明显的生物地球化学分带性,从氧化带到还原带,喜氧菌数量逐渐减少,厌氧菌数量递增,各带细菌的分布受容矿层中有机碳含量、铁的存在形式及含量、所赋存地下水的溶解氧和硫酸盐含量等的控制。微生物对铀成矿的影响是综合性的,同时也受到各种环境因素的制约,微生物之间也存在着共生、互生、竞争和拮抗的关系,从而影响着矿床的发育。该类铀矿床微生物富集铀的机制是以间接的非代谢性生物吸附为主,而代谢性富集机制则是次要的。     

Anaerobic Metabolism in Tidal Freshwater Wetlands: I. Plant Removal Effects on Iron Reduction and Methanogenesis

For energetic reasons, iron reduction suppresses methanogenesis in tidal freshwater wetlands; however, when iron reduction is limited by iron oxide availability, methanogenesis dominates anaerobic carbon mineralization. Plants can mediate this microbial competition by releasing oxygen into the rhizosphere and supplying oxidized iron for iron reducers. We utilized a plant removal experiment in two wetland sites to test the hypothesis that, in the absence of plants, rates of iron reduction would be diminished, allowing methanogenesis to dominate anaerobic metabolism. In both sites, methanogenesis was the primary anaerobic mineralization pathway, with iron reduction dominating only early and late in the growing season in the site with a less organic soil. These patterns were not influenced by the presence of plants, demonstrating that plants were not a key control of microbial metabolism. Instead, we suggest that site conditions, including soil chemistry, and temperature are important controls of the pathways of anaerobic metabolism.     

冲绳海槽中部热液活动与IODP331航次初步成果

伊平屋北部热液区（IheyaNoAhhydrothermalfield）位于冲绳海槽中部地区。综合大洋钻探计划（IODP）331航次于2010年9月1日至10月4日在该区钻探了5个站位（C0013-C0017）：C0016站位位于NoahBigChimney（NBC）地区活跃的热液烟囱和硫化物-硫酸盐丘状体上;在C00...     

Model for the distribution of sulfate reduction and methanogenesis in freshwater sediments

A model, based on the in situ physiological characteristics of methanogens and sulfate reducers, was developed to describe the distribution of methanogenesis and sulfate reduction in freshwater sediments. The model predicted the relative importance of methane production and sulfate reduction in lakes of various trophic status and generated profiles of sulfate, acetate, methanogenesis, and sulfate reduction comparable to the profiles that are expected based on field studies. The model indicated that at sulfate concentrations greater than 30μM a sulfate-reducing zone develops because sulfate reducers maintain acetate concentrations too low for methanogens to grow. At lower sulfate concentrations a methanogenic zone develops because the dual limitations of low sulfate concentrations and acetate consumption by methanogens prevents sulfate reducers from growing. The model and a compilation of previously published field data indicate that, within the reported range of sulfate concentrations, the relative importance of methanogenesis and sulfate reduction in freshwater sediments is primarily dependent upon the rates of organic matter decomposition.     

陆架边缘海沉积物有机碳矿化及其对海洋碳循环的影响

边缘海沉积物是海洋重要的碳储库,其内部的碳循环主要是由有机质矿化分解过程来驱动的。有机碳进入边缘海沉积物后,矿化分解为溶解无机碳(DIC)进入沉积物孔隙水并扩散到上层水柱,参与海洋系统碳循环;同时还有部分DIC与钙镁等离子结合形成自生碳酸盐,保存于沉积物碳库。从生物地球化学角度探讨有机质埋藏机制和效率,在此基础上重点综述沉积物硫酸盐还原、产甲烷和甲烷厌氧氧化过程的耦合机制,以及有机质矿化对自生碳酸盐形成的影响等方面的研究进展,以期加深对陆架边缘海沉积物在全球碳循环收支平衡中的作用及其气候环境效应的认识。     

Microbial Geochemical Characteristics of the Coalbed Methane in the Shizhuangnan Block of Qinshui Basin,North China and their Geological Implications

Methanogens and sulfate reducing bacteria were detected by the 16SrRNA sequencing of coalbed methane(CBM)co-produced water in the south of the Qinshui Basin,which is indicative of the presence of secondary biological gas in the south of this basin,in contradiction to the previous understanding of thermogenic gas.This work systematically collected water samples from the CBM wells in the Shizhuangnan Block and analyzed the microbial geochemical characteristics from the aspects of water ions,hydrogen and oxygen isotopes,dissolved inorganic carbon and microbial diversity.It is shown that the Shizhuangnan Block has a nearly SN-trending monoclinic structure,and the elevation of coal seam decreases gradually from the east to west.Because of the water blocking effect of Sitou fault in the west,the precipitation flowed from the east to west,and gradually transited to stagnant flow area.The concentration variation of some ions such as Na~+,K~+,Ca~(2+),Mg~(2+),Cl~-,HCO~-_3 and total dissolved solids(TDS)suggest the variation of redox condition in the coal reservoir water.The 16SrDNA sequencing analysis of the collected water samples detected the presence of methanogens and sulfate reduction bacteria.The presence of methane production zone and sulfate methane transition zone(SMTZ)was identified.The effect of methanogens in the methane production zone leads to an increase in the methane concentration,resulting in a high gas content in the study area.In the SMTZ,most methane is consumed by anaerobic oxidation due to high sulfate concentrations.     

Microbial Mats in the Mesoproterozoic Carbonates of the North China Platform and Their Potential for Hydrocarbon Generation

The well-preserved Mesoproterozoic succession in the North China platform consists mainly of three llthological associations including peritidal quartz sandstone, shallow marine and lagoonai dark to black shales, and shallow epeiric carbonates, with a total thickness of up to 8 000 m. In addition to well-documented microplants, macroalgae, and microbial buildups, abundant microbially induced sedimentary structures (MISS) and mat-related sediments have been recognized in these rocks. Intensive microbial mat layers and MISS are especially well preserved in the carbonates of the upper Gaoyuzhuang (高于庄) (ca. 1.5 Ga) and lower Wumishan (雾迷山) (ca. 1.45 Ga) formations, Indicating diversified microbial activities and a high organic production. In these petrified blomats, putative microbial fossils (both coccoidal and filamentous) and framboidal pyrites have been identified. The abundance of authigenic carbonate minerals in the host rocks, such as, acicular aragnnites, rosette barites, radial siderites, ankerites, and botryoidai carbonate cements, suggests authigenlc carbonate precipitation from anaerobic oxidation of methane (AOM) under anoxic/euxinic conditions. Warm climate and anoxic/euxinic conditions in the Mesoproterozoic oceans may have facilitated high microbial productivity and organic burial in sediments. Although authigenic carbonate cements may record carbonate precipitation from anaerobic methane oxidation, gas blister (or dome) structures may indicate gas release from active methanogenesls during shallow burial Bituminous fragments in mat-related carbonates also provide evidence for hydrocarbon generation. Under proper conditions, the Mesoproterozoic mat-rich carbonates will have the potential for hydrocarbon generation and serve as source rocks. On the basis of petrified biomats, a rough estimation suggests that the Mesoproterozoic carbonates of the North China platform might have a hydrocarbon production potential in theorder of 10×108t.     

Estimation of the global amount of submarine gas hydrates formed via microbial methane formation based on numerical reaction-transport modeling and a novel parameterization of Holocene sedimentation

This study provides new estimates for the global offshore methane hydrate inventory formed due to microbial CH₄ production under Quaternary and Holocene boundary conditions. A multi-1D model for particular organic carbon (POC) degradation, gas hydrate formation and dissolution is presented. The novel reaction-transport model contains an open three-phase system of two solid compounds (organic carbon, gas hydrates), three dissolved species (methane, sulfates, inorganic carbon) and one gaseous phase (free methane). The model computes time-resolved concentration profiles for all compounds by accounting for chemical reactions as well as diffusive and advective transport processes. The reaction module builds upon a new kinetic model of POC degradation which considers a down-core decrease in reactivity of organic matter. Various chemical reactions such as organic carbon decay, anaerobic oxidation of methane, methanogenesis, and sulfate reduction are resolved using appropriate kinetic rate laws and constants. Gas hydrates and free gas form if the concentration of dissolved methane exceeds the pressure, temperature, and salinity-dependent solubility limits of hydrates and/or free gas, with a rate given by kinetic parameters. Global input grids have been compiled from a variety of oceanographic, geological and geophysical data sets including a new parameterization of sedimentation rates in terms of water depth.We find prominent gas hydrate provinces offshore Central America where sediments are rich in organic carbon and in the Arctic Ocean where low bottom water temperatures stabilize methane hydrates. The world’s total gas hydrate inventory is estimated at (at STP conditions) or, equivalently, 4.18-995 Gt of methane carbon. The first value refers to present day conditions estimated using the relatively low Holocene sedimentation rates; the second value corresponds to a scenario of higher Quaternary sedimentation rates along continental margins.Our results clearly show that in-situ POC degradation is at present not an efficient hydrate forming process. Significant hydrate deposits in marine settings are more likely to have formed at times of higher sedimentation during the Quaternary or as a consequence of upward fluid transport at continental margins.     

Geochemical constraints on chemolithoautotrophic metabolism by microorganisms in seafloor hydrothermal systems

Mixing of hydrothermal fluids and seawater at the ocean floor, combined with slow reaction kinetics for oxidation/reduction reactions, provides a source of metabolic energy for chemolithotrophic microorganisms which are the primary biomass producers for an extensive submarine ecosystem that is essentially independent of photosynthesis. Thermodynamic models are used to explore geochemical constraints on the amount of metabolic energy potentially available from chemosynthetic reactions involving S, C, Fe, and Mn compounds during mixing of hydrothermal fluids with seawater. For the vent fluid used in the calculations (EPR 21 degrees N OBS), the model indicates that mixing environments are favorable for oxidation of H2S, CH4, Fe2+ and Mn2+ only below approximately 38 degrees C, with methanogenesis and reduction of sulfate or S degrees favored at higher temperatures, suggesting that environments dominated by mixing provide habitats for mesophilic (but not thermophilic) aerobes and thermophilic (but not mesophilic) anaerobes. A maximum of approximately 760 cal per kilogram vent fluid is available from sulfide oxidation while between 8 and 35 cal/kg vent fluid is available from methanotrophy, methanogenesis, oxidation of Fe or Mn, or sulfate reduction. The total potential for chemosynthetic primary production at deep-sea hydrothermal vents globally is estimated to be about 10(13) g biomass per year, which represents approximately 0.02% of the global primary production by photosynthesis in the oceans. Thermophilic methanogens and sulfate- and S degree-reducers are likely to be the predominant organisms in the walls of vent chimneys and in the diffuse mixing zones beneath warm vents, where biological processes may contribute to the high methane concentrations of vent fluids and heavy 34S/32S ratios of vent sulfide minerals. The metabolic processes taking place in these systems may be analogs of the first living systems to evolve on the Earth.     

Sedimentary Organic Carbon Mineralization and Its Contribution to the Marine Carbon Cycle in the Marginal Seas

Continental margin sediments are important ocean carbon repository, and the internal carbon cycle is mainly driven by the mineralization processes of sedimentary organic matter. Most organic carbon is transformed to Dissolved Inorganic Carbon (DIC) by mineralization processes after being delivered to continental margin sediments, and DIC from pore water diffuses into the upper water column and participates in the ocean carbon cycle. At the same time, some DIC combines ions such as Ca²⁺ and Mg²⁺ and precipitates as authigenic carbonate minerals so that carbon is stored in the deposits. Based on the biogeochemical study of the mechanism and efficiency of organic matter burial, we discussed the interaction among sulfate reduction, methanogenesis and anaerobic oxidation of methane, and the effect of organic mineralization on the formation of authigenic carbonate. By reviewing the above-mentioned aspects, we can obtain a better understanding of the role of continental margin sediments in the global carbon cycling budgets as well as its climate and environmental effects.