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1.
《海洋学研究》2013,(3)
南海东沙群岛东北部海洋Ⅳ号地区GC16站重力柱状沉积物中的有机碳、总氮,以及自生碳酸盐岩矿物的无机碳同位素组成分析结果表明,甲烷流体活动区硫酸盐-甲烷转换带(SMTZ—sulfate methane transition zone)是重要的生物地球化学界面,该带内沉积物中有机碳、氮与无机碳同位素组成变化明显。GC16站SMTZ上界面以下的沉积物中有机碳、氮同位素组成分别比其上的沉积物负偏1.4‰PDB和0.93‰,反映该带内甲烷缺氧氧化作用(AOM—anaerobic oxidation of methane)与氨氧化作用发育。无机碳同位素组成表明SMTZ界面之下沉积物中的自生碳酸盐岩矿物为以微生物为媒介的甲烷驱动成因,地质历史时期(至柱状沉积物底部沉积时期)曾发生过2次较强烈的CH4流体活动;目前该区甲烷流体活动较弱,甲烷流体影响深度与SMTZ上界面一致,未能到达海底。 相似文献
2.
南海东沙群岛东北部海洋IV号地区GC16站重力柱状沉积物中的有机碳、总氮,以及自生碳酸盐岩矿物的无机碳同位素组成分析结果表明,甲烷流体活动区硫酸盐甲烷转换带(SMTZ—sulfate methane transition zone)是重要的生物地球化学界面,该带内沉积物中有机碳、氮与无机碳同位素组成变化明显。GC16站SMTZ上界面以下的沉积物中有机碳、氮同位素组成分别比其上的沉积物负偏1.4‰PDB和0.93‰,反映该带内甲烷缺氧氧化作用(AOM—anaerobic oxidation of methane)与氨氧化作用发育。无机碳同位素组成表明SMTZ界面之下沉积物中的自生碳酸盐岩矿物为以微生物为媒介的甲烷驱动成因,地质历史时期(至柱状沉积物底部沉积时期)曾发生过2次较强烈的CH4流体活动;目前该区甲烷流体活动较弱,甲烷流体影响深度与SMTZ上界面一致,未能到达海底。 相似文献
3.
利用孔隙水化学和稳定同位素化学等方法分析珠江口红树林湿地沉积层孔隙水硫酸根(SO_4~(2-))、游离甲烷气体(CH_4)、总溶解无机碳(DIC)以及δ13CDIC的垂直剖面分布特征.结果显示,孔隙水SO_4~(2-)浓度自表至底呈线性梯度减小,至硫酸盐-甲烷界面(SMI)附近,硫酸盐几乎全部消耗,而CH_4浓度急剧增大,KC1、KC3、KC4、K17和K10等5个站位SMI深度分别为20、50、70、80、50 cm,SMI深度由红树林湿地林间向光滩逐渐增大.同时,孔隙水DIC浓度在该深度明显升高,沉积物发生强烈的甲烷厌氧氧化(AOM)作用.在AOM过程中,由于12CH_4氧化速率较13CH_4快,故引起沉积物孔隙水δ13CDIC偏轻.沉积层中的有机质含量及其活性高低是制约沉积物SMI分布深浅的关键因素,高含量的活性有机质可加速孔隙水SO_4~(2-)再矿化过程的消耗,使得通过AOM作用的SO_4~(2-)消耗通量相应增大.在微生物作用下,部分活性有机质被大量消耗,致使进入沉积物SO_4~(2-)还原带的活性有机质数量相应减少,从而引起部分SO_4~(2-)转为与CH_4发生反应促进AOM作用. 相似文献
4.
利用化学和稳定同位素化学等方法分析研究区沉积物间隙水甲烷和硫酸根、pH和∑CO2以及δ^13C—CH4和δ^13C—ECO2的垂直剖面分布。结果显示，间隙水硫酸根浓度呈线性梯度减小，至沉积物甲烷-硫酸盐界面（sulfate-methane interface，SMI）附近，硫酸盐几乎全部消耗而甲烷浓度急剧增大；与此同时，间隙水pH和∑CO2在该深度位置明显升高。间隙水地球化学特征揭示了沉积物发生了AOM作用。在AOM过程中，由于^12CH4氧化速率较^13CH4快，故引起沉积物间隙水剩余甲烷的碳同位素偏重，而δ^13C—ZCO2值变为极负，珠江口QA11—2、QA12-9、QA12—14和GS-1四个站位SMI对应深度分别为12cm、38cm、50cm和204cm，而南海BD-7站位由间隙水硫酸根剖面变化推算约为600cm。从珠江河口到南海沉积物，由于受陆源输入的减少，表层沉积物有机质含量呈降低趋势。有机质输入量及其活性的高低是制约了沉积物SMI分布深浅的关键因素，这是由于高含量的活性有机质一方面可加速间隙水硫酸根通过有机质再矿化分解作用途径消耗；另一方面可引起向上扩散进入AOM反应带的甲烷通量增大，使得通过AOM作用的硫酸根消耗通量相应增大，其结果造成沉积物SMI的上移。根据沉积物C／N比值以及^13C剖面变化，推断AOM作用的可能发生机制是由于在沉积物表层再矿化作用过程中，因一部分活性有机质被大量消耗，导致进入沉积物硫酸根还原带底部的活性有机质数量相应减少，从而引起部分硫酸根转为与甲烷发生反应，并在微生物的作用下完成AOM过程。 相似文献
5.
在天然气水合物发育区海底沉积物中甲烷厌氧氧化作用(AOM)是碳循环的重要组成部分。通过定量计算表层沉积物中甲烷迁移转化通量,可以更准确评估甲烷来源碳对沉积物碳库和海洋深部碳库影响。本文利用反应―运移模型对采集于南海神狐水合物发育区两个站位(SH-W19-PC、SH-W23-PC)采集的孔隙水SO_4~(2-)、溶解无机碳(DIC)、Ca~(2+)剖面进行拟合,同时对DIC碳同位素进行分析,确定近海底沉积物中的碳循环。研究显示两个站位孔隙水中SO_4~(2-)和Ca~(2+)浓度在剖面上随深度呈线性减少,DIC浓度随深度逐渐增加,其δ~(13)C_(DIC)值随深度逐渐降低至约-25‰,表明两个站位存在一定程度的AOM。模拟计算两个站位沉积物孔隙水溶解甲烷向上的通量分别为25.9和18.4 mmol·m~(-2) a~(-1),AOM作用产生的DIC分别占其总DIC量的70.7%和60%。由沉积物向海水中释放的DIC通量占DIC汇的约60%。因此,在天然气水合物发育区向海底渗漏甲烷大部分以DIC的形式进入上覆海水,这些具有极负碳同位素值的甲烷来源的DIC可能对局部深海碳库产生一定的影响。 相似文献
6.
南海北部浅表层沉积底栖有孔虫碳同位素及其对富甲烷环境的指示 总被引：3，自引：0，他引：3
对南海北部陆坡东沙海域、神狐海域及西沙海槽甲烷渗漏环境和无甲烷渗漏环境87个浅表层沉积物中的底栖有孔虫Uvigerinaspp.进行碳同位素分析研究,结果表明,东沙海域δ13C值为-0.52‰~-5.68‰,平均值为-1.41‰,出现明显的负偏移;神狐海域δ13C值介于-0.36‰~-1.10‰,平均值为-0.75‰,未见明显的δ13C值负偏移;西沙海槽δ13C值介于-0.01%~-0.89‰,平均值为-0.45‰;对Uvigerinaspp.碳同位素组成与沉积物有机碳(TOC)、甲烷(CH4)间的关系进行探讨,发现δ13C负偏移主要出现在甲烷渗漏环境,发生在末次盛冰期,与溶解无机碳负偏移以及沉积物全样的δ13C值负偏移层位相吻合,有可能作为富甲烷环境的替代指标。 相似文献
7.
海洋沉积物中的硫酸盐-甲烷反应界面（SMI）的深度变化能够指示下伏甲烷水合物的赋存状态。本文通过对南海北部陆坡天然气水合物潜在分布区沉积物间隙水化学和自生碳酸盐氧、碳同位素组成资料系统分析和对比,探讨了南海北部陆坡沉积物的SMI深度空间变化对下伏甲烷水合物的赋存状态的指示意义。结果表明,南海北部陆坡沉积物的SMI的深度呈现出从西南-东北变浅的趋势,这一趋势与自生碳酸盐的碳同位素组成揭示的甲烷释放量增大趋势有很好的对应关系,进而表明在南海北部陆坡从西南-东北甲烷水合物的埋藏深度变浅或者甲烷水合物的分解程度增大。 相似文献
8.
冷泉渗漏区海底微生物作用及生物标志化合物 总被引：8，自引：0，他引：8
在有冷泉活动和水合物产出的海底环境中,甲烷氧化古细菌和硫酸盐还原细菌十分发育,它们主导着海底天然气(主要是甲烷)的缺氧氧化作用,并在海底碳循环和生物种群繁衍中发挥着重要作用。海底天然气渗漏活动区的甲烷氧化古细菌使渗漏CH4缺氧氧化为HCO3-,硫酸盐还原细菌使SO42-转化为HS-,从而使细菌微生物获得生命所需的能量,生物种群得以发育和繁衍。甲烷氧化古细菌有ANME-1、ANME-2、ANME-3三个种群,形成相应的醚类异戊二烯类和类异戊二烯烃类生物标志物。硫酸盐还原细菌有Desulfosarcina和Desulfococcus两个主要的细菌群落,形成二烃基甘油二醚和脂肪酸生物标志化合物。这种天然气渗漏区内微生物活动产生的生物标志化合物都具有特别负的碳同位素组成,δ13C值为-41.1‰~-95.6‰,说明微生物群落在生命代谢过程中摄取了来自甲烷的碳,同时也反映了天然气渗漏系统缺氧带存在的古细菌和硫酸盐还原细菌活动。 相似文献
9.
《海洋地质与第四纪地质》2015,(5)
甲烷渗漏活动及其甲烷厌氧氧化(AOM)在自生碳酸盐岩沉淀的同时,也通过影响孔隙水溶解无机碳(DIC)进而影响着周围环境中底栖有孔虫,以往的文章鲜有报道二者的耦合响应。研究开展了综合大洋钻探计划IODP 311航次两个钻孔(1328和1329)中获得的自生碳酸盐岩和底栖有孔虫(Uvigerina peregrina)同位素研究,发现晚更新世以来多个层位获得的自生碳酸盐岩和底栖有孔虫的稳定碳同位素变化趋势均呈现一致的负偏碳同位素特征,但是,同层位的自生碳酸盐岩碳同位素负偏程度要比底栖有孔虫大一个数量级。自生碳酸盐岩与底栖有孔虫碳同位素变化趋势的一致性表明二者对于甲烷渗漏作用有较好的共同响应。AOM作用对孔隙水中溶解无机碳(DIC)的影响可在重碳酸氢根通过局部环境的过饱和沉淀自生碳酸盐岩的同时,也能部分参与底栖有孔虫的成壳,两者在成因方面是耦合的。综合结合自生碳酸盐岩和底栖有孔虫的碳同位素特征可以避免单一载体易受后期成岩改造影响而掩盖甲烷渗漏活动的识别。 相似文献
10.
南海东北部甲烷成因碳酸盐岩的矿物学及同位素组成(英文) 总被引：1，自引：0，他引：1
取自南海北部的3块自生碳酸盐岩主要为圆环状、结核状和结壳状。X射线衍射分析显示,这3件碳酸盐岩主要由黏土矿物、陆源碎屑(石英、长石)和碳酸盐矿物(高镁方解石和铁白云石)组成;碳氧同位素分析表明,结核状和结壳状碳酸盐岩具有极负的δ13C(分别为-32.83‰和-38.01‰PDB)和正的δ18O(分别为+2.19‰和+2.96‰PDB),不同于正常沉积的海相碳酸盐岩,甲烷厌氧氧化过程控制了这些碳酸盐岩的形成。碳酸盐岩为甲烷成因,记录了南海东北部海底富含甲烷的冷泉活动历史。 相似文献
11.
光和温度对两种绿潮藻光合途径及抗氧化功能的影响 总被引：1，自引：0，他引：1
绿潮是潮间带绿藻大量增殖形成的高生物量生态灾害，其暴发不仅受到温度、营养盐等环境因素的驱动，而且与自身光合能力的强弱密切相关。本研究以绿潮物种—肠浒苔(Ulva intestinalis)和Ulva expansa为研究对象，通过室外培养实验，检测了它们在夏季高温、高光强条件下的光合途径与抗氧化生理特征，并分析了与光合产物的对应关系。研究结果表明，肠浒苔与U. expansa的光合途径与抗氧化能力存在显著差异。前者的C4光合途径关键酶活性在光合作用过程中出现高表达特征，与光、温度存在显著相关性，C3光合途径关键酶活性在中午受到强光抑制；组织δ13C的变化范围为?17.1‰～?15.7‰，表明其光合作用可能由C3和C4途径共同参与。后者的C4光合途径关键酶活性表达较弱，且与光、温度不存在显著相关性，C3光合途径关键酶活性没有出现明显的光抑制现象；组织δ13C的范围为?23.5‰～?21.9‰，表明其光合作用主要依靠C3途径进行。此外，肠浒苔在培养过程中表现出了较强的抗氧化能力，可能与其在高温、高光强条件下启动C4光合途径密切相关。肠浒苔与U. expansa的比较研究说明，藻类C4光合途径存在显著种间差异性。 相似文献
12.
Franklin S. Kinnaman Justine B. Kimball Luis Busso Daniel Birgel Haibing Ding Kai-Uwe Hinrichs David L. Valentine 《Geo-Marine Letters》2010,30(3-4):355-365
The Coal Oil Point seep field located offshore Santa Barbara, CA, consists of dozens of named seeps, including a peripheral ～200 m2 area known as Brian Seep, located in 10 m water depth. A single comprehensive survey of gas flux at Brian Seep yielded a methane release rate of ～450 moles of CH4 per day, originating from 68 persistent gas vents and 23 intermittent vents, with gas flux among persistent vents displaying a log normal frequency distribution. A subsequent series of 33 repeat surveys conducted over a period of 6 months tracked eight persistent vents, and revealed substantial temporal variability in gas venting, with flux from each individual vent varying by more than a factor of 4. During wintertime surveys sediment was largely absent from the site, and carbonate concretions were exposed at the seafloor. The presence of the carbonates was unexpected, as the thermogenic seep gas contains 6.7% CO2, which should act to dissolve carbonates. The average δ13C of the carbonates was ?29.2?±?2.8‰ VPDB, compared to a range of ?1.0 to +7.8‰ for CO2 in the seep gas, indicating that CO2 from the seep gas is quantitatively not as important as 13C-depleted bicarbonate derived from methane oxidation. Methane, with a δ13C of approximately ?43‰, is oxidized and the resulting inorganic carbon precipitates as high-magnesium calcite and other carbonate minerals. This finding is supported by 13C-depleted biomarkers typically associated with anaerobic methanotrophic archaea and their bacterial syntrophic partners in the carbonates (lipid biomarker δ13C ranged from ?84 to ?25‰). The inconsistency in δ13C between the carbonates and the seeping CO2 was resolved by discovering pockets of gas trapped near the base of the sediment column with δ13C-CO2 values ranging from ?26.9 to ?11.6‰. A mechanism of carbonate formation is proposed in which carbonates form near the sediment–bedrock interface during times of sufficient sediment coverage, in which anaerobic oxidation of methane is favored. Precipitation occurs at a sufficient distance from active venting for the molecular and isotopic composition of seep gas to be masked by the generation of carbonate alkalinity from anaerobic methane oxidation. Figure
Processes modulating carbonate formation at Brian Seep (California) during times of high and low sediment burden 相似文献
13.
Nicolas Chevalier Ioanna Bouloubassi Alina Stadnitskaia Marie-Hélène Taphanel Jaap S. Sinninghe Damsté 《Geo-Marine Letters》2014,34(2-3):269-280
Distributions and carbon isotopic compositions of microbial lipid biomarkers were investigated in sediment cores from the G11 and G12 pockmarks in the Nyegga sector of the Storegga Slide on the mid-Norwegian margin to explore differences in depth zonation, type and carbon assimilation mode of anaerobic methane-oxidizing archaea (ANMEs) and associated sulphate-reducing bacteria responsible for anaerobic oxidation of methane (AOM) in these cold seep environments. While the G11 site is characterised by black reduced sediments colonized by gastropods and Siboglinidae tubeworms, the G12 site has black reduced sediments devoid of fauna but surrounded by a peripheral occurrence of gastropods and white filamentous microbial mats. At both sites, bulk sediments contained abundant archaeal and bacterial lipid biomarkers substantially depleted in 13C, consisting mainly of isoprenoidal hydrocarbons and dialkyl glycerol diethers, fatty acids and non-isoprenoidal monoalkylglycerol ethers. At the G11 site, down-core profiles revealed that lipid biomarkers were in maximum abundance from 10 cm depth to the core bottom at 16 cm depth, associated with δ13C values of ?57 to ?136‰. At the G12 site, by contrast, lipid biomarkers were in high abundance in the upper 5 cm sediment layer, associated with δ13C values of ?43 to ?133‰. This suggests that, as expected from the benthic fauna characteristics of the sites, AOM takes place mainly at depth in the G11 pockmark but just below the seafloor in the G12 pockmark. These patterns can be explained largely by variable fluid flow rates. Furthermore, at both sites, a dominance of ANME-2 archaea accompanied by their bacterial partners is inferred based on lipid biomarker distributions and carbon isotope signatures, which is in agreement with recently published DNA analyses for the G11 pockmark. However, the present data reveal high discrepancies in the contents and δ13C values for both archaeal and bacterial lipid profiles, implying the possible involvement of at least two distinct AOM-related microbial consortia at the inferred AOM depth zonation of G11 and G12 pockmark sediments. In both sediment cores, the δ13C profiles for most archaeal lipids suggest a direct assimilation of dissolved inorganic carbon (DIC) in addition to methane by ANMEs (chemoautotrophy); constant and highly depleted δ13C profiles for PMI:3, an archaeal lipid biomarker presumably related to ANME-2, suggest a direct assimilation of 13C-depleted methane-derived carbon via AOM (methanotrophy). Evidently, the common approach of investigating lipid biomarker contents and δ13C signatures in cold seep sediments does not suffice to precisely discriminate between the carbon assimilation mode for each ANME archaeal group and associated bacteria. Rather, this needs to be combined with further specific labelling studies including different carbon sources (methane carbon, methane-derived organic intermediates and DIC) in order to unravel the metabolic pathways of each microbial consortium involved in AOM (ANME-1 vs. ANME-2 vs. ANME-3 archaeal group and associated bacteria). 相似文献
14.
The sedimentary system of Kalimantan has undergone significant development since the Oligocene. Previous research have largely ignored the capacity of the Cretaceous–Eocene sediments to produce hydrocarbons,focusing instead primarily on the Oligocene–Miocene coal as the principal source rocks. Shales and coals from the outcrops in the northern margin of Kalimantan were analyzed with palynological and geochemical methods to characterize the palaeoenvironmental and palaeoecological differences bet... 相似文献
15.
Catherine Pierre Germain Bayon Marie-Madeleine Blanc-Valleron Jean Mascle Stéphanie Dupré 《Geo-Marine Letters》2014,34(2-3):253-267
On the passive margin of the Nile deep-sea fan, the active Cheops mud volcano (MV; ca. 1,500 m diameter, ~20–30 m above seafloor, 3,010–3,020 m water depth) comprises a crater lake with hot (up to ca. 42 °C) methane-rich muddy brines in places overflowing down the MV flanks. During the Medeco2 cruise in fall 2007, ROV dives enabled detailed sampling of the brine fluid, bottom lake sediments at ca. 450 m lake depth, sub-surface sediments from the MV flanks, and carbonate crusts at the MV foot. Based on mineralogical, elemental and stable isotope analyses, this study aims at exploring the origin of the brine fluid and the key biogeochemical processes controlling the formation of these deep-sea authigenic carbonates. In addition to their patchy occurrence in crusts outcropping at the seafloor, authigenic carbonates occur as small concretions disseminated within sub-seafloor sediments, as well as in the bottom sediments and muddy brine of the crater lake. Aragonite and Mg-calcite dominate in the carbonate crusts and in sub-seafloor concretions at the MV foot, whereas Mg-calcite, dolomite and ankerite dominate in the muddy brine lake and in sub-seafloor concretions near the crater rim. The carbonate crusts and sub-seafloor concretions at the MV foot precipitated in isotopic equilibrium with bottom seawater temperature; their low δ13C values (–42.6 to –24.5‰) indicate that anaerobic oxidation of methane was the main driver of carbonate precipitation. By contrast, carbonates from the muddy lake brine, bottom lake concretions and crater rim concretions display much higher δ13C (up to –5.2‰) and low δ18O values (down to –2.8‰); this is consistent with their formation in warm fluids of deep origin characterized by 13C-rich CO2 and, as confirmed by independent evidence, slightly higher heavy rare earth element signatures, the main driver of carbonate precipitation being methanogenesis. Moreover, the benthic activity within the seafloor sediment enhances aerobic oxidation of methane and of sulphide that promotes carbonate dissolution and gypsum precipitation. These findings imply that the coupling of carbon and sulphur microbial reactions represents the major link for the transfer of elements and for carbon isotope fractionation between fluids and authigenic minerals. A new challenge awaiting future studies in cold seep environments is to expand this work to oxidized and reduced sulphur authigenic minerals. 相似文献
16.
大河影响下的陆架边缘海沉积有机碳的分布和来源是全球碳循环研究的重要内容。本研究于2012年5月采集了渤海海域的29个表层沉积物样品,分析了粒度组成、总有机碳(TOC)、总氮(TN)、木质素含量和稳定碳同位素丰度(δ13C)等参数,结合基于蒙特卡洛模拟的三端元混合模型,定量研究了沉积物中有机碳的分布和来源情况,并讨论了其影响因素。结果表明,研究区域表层沉积物中TOC含量为0.19%~0.81%,渤海中部泥质区站位(大于0.65%)明显高于其周围砂质区域站位(小于0.40%);TOC与黏土含量也有显著的正相关性,说明细颗粒沉积物容易富集有机碳。沉积有机碳的δ13C范围为-23.7‰~-21.8‰,显示沉积有机碳是海源和陆源有机碳的混合输入。木质素参数,如C/V、S/V和LPVI的数值范围显示研究区域表层沉积物中木质素主要来源于被子植物草本组织与木本组织的混合,同时有少量裸子植物的贡献。基于蒙特卡洛模拟的三端元混合模型显示研究区域沉积物中有机碳主要来源于海洋浮游植物,平均为64%,陆源有机碳中来自土壤的贡献最高(平均为27%),C3维管植物的贡献较少(平均为9%)。海洋浮游植物有机碳主要分布在渤海中部泥质区及离岸较远的区域,而土壤有机碳和C3维管植物有机碳则主要沉积在河口附近及近岸区,并可以离岸输运到较远的地方。 相似文献
17.
Jingqi Xu 《海洋学报(英文版)》2023,42(3):76-88
The hydrocarbon gases in the L1 gas field of the Lishui-Jiaojiang Sag have been commonly interpreted to be an accumulation of pure sapropelic-type thermogenic gas. In this study, chemical components, stable isotopic compositions, and light hydrocarbons were utilized to shed light on the origins of the hydrocarbon fluids in the L1gas pool. The hydrocarbon fluids in the L1 gas pool are proposed to be a mixture of three unique components:mid-maturity oil from the middle Paleocene coastal marine Lin... 相似文献
18.
中华绒螯蟹幼蟹维生素C营养需求研究 总被引：9，自引：0，他引：9
在每100g等氮、等能纯化饲料中分别添加0,100,200,400,800,1 000mg维生素C(Vc)多聚磷酸酯(LAPP),用这样配制成的试验饲料饲喂已淡化5d的河蟹大眼幼体及后续幼蟹25d,探讨Vc对大眼幼体和幼蟹生长、存活、蜕壳频率及抗逆性的影响,同时探明幼蟹对Vc的适宜需求量,结果表明,饲料Vc添加量为100~400mg/100g时,可以保证幼蟹正常生长、存活和蜕皮,尤其以投喂添加Vc200mg/100g(C2组)和400mg/100g(C3组)饲料的Ⅲ期幼蟹增重率、存活率和平均蜕皮频率较高,其中C2组(上述各指标值)分别为516.18%,62.83%,2.58,C3组分别为458.89%,66.17%,2.61;饲料中缺少Vc时(如C0组),Ⅲ期幼蟹的增重率、存活率和平均蜕皮频率最低,分别为265.31%,26.67%和2.26.饲料中Vc的添加量达到800mg/100g(C4)和1 000mg/100g(C5)时,幼蟹的蜕皮反而受到抑制,平均蜕皮频率降低,蜕皮周期延长,且存活率降低,到Ⅲ期幼蟹的增重率、存活率和平均蜕皮频率在C4组分别为355.7%,31.33%,2.39,在C5组分别为307.53%,28.56%,2.19.此外,各处理组幼蟹对抗逆性影响的试验表明,在一定的范围内,饲料中添加Vc能提高幼蟹的耐低氧能力和耐pH突变能力,而对耐盐度突变能力没有明显的影响.综合上述结果可以得出,为保持幼蟹良好生产性能,饲料中添加的Vc? 相似文献
19.
通过对两根沉积柱GHE27L和GHE24L的总有机碳（TOC）、总氮（TN）、C/N比值及稳定碳同位素（δ13Corg）的分析,本文探讨了21.1 ka BP以来南海北部陆坡神狐海域沉积有机质的组成特征及可能的古气候/环境信息。沉积柱GHE27L的TOC含量、TN含量、C/N比值及δ13Corg值分别为0.53%~1.81%,0.07%~0.18%,8.2~16.0和-23.6‰~-20.3‰。沉积柱GHE24L各参数则分布为0.45%~1.65%,0.09%~0.24%,5.3~12.2和-22.6‰~-20.4‰。沉积柱总体有机质的剖面变化显示,末次盛冰期以来南海北部沉积有机质具有海洋和陆地混合来源,但以海洋有机质来源为主。冰期陆源有机质对总有机质的相对贡献比全新世高。末次盛冰期南海北部气候相对干旱,C4植被发育。全新世夏季风增强、降雨增多。自2.0 ka BP以来,人类活动对南海北部海洋初级生产力产生一定的影响。 相似文献