30 resultados para DIC

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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本文研究了三株铜绿微囊藻在不同条件下光合放氧对外源溶解无机碳的响应。当温度从20℃上升到30℃时,三株铜绿微囊藻的光合放氧速率都显著增加。随着反应介质pH值从7.0上升到9.0,铜绿微囊藻的光合放氧逐渐增强,其最大光合放氧速率显著增大。胞外碳酸酐酶抑制剂乙酰唑胺(acetazolamide,AZ)对铜绿微囊藻的光合放氧无显著影响,而碳酸酐酶抑制剂乙氧苯丙噻唑磺胺(ethoxyzolamide,EZ)则抑制其光合放氧。通过酶动力学方程拟合,得出这三株铜绿微囊藻的表观无机碳亲和力常数K0.5(DIC)均低于5

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为了研究短期太阳紫外辐射对钝顶螺旋藻的影响,作者将静止和充气培养的藻体,暴露在全波长太阳辐射PAB(PAR+UVA+UVB),去除UVB辐射PA(PAR+UVA)及切断所有紫外辐射的光合有效辐射P(PAR)三种光处理条件下,测定了其光化学效率的变化。结果表明,紫外辐射(UVP)及光合有效辐射(PAR)均能导致钝顶螺旋藻的光化学效率降低,表现出了明显的光抑制,但是,UVR可导致更大程度的光抑制。充气培养条件下,与早晨(07:00)初始值相比,PAR导致了11%~20%的光抑制,而UVR(PAB-P)所产生的

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The physiological responses of Nitzschia palea Kutzing, a freshwater diatom, to elevated CO2 were investigated and compared with those of a marine diatom, Chaetoceros muelleri Lemmermann previously reported. Elevated CO2 concentration to 700 mu l/L increased the dissolved inorganic carbon (DIC) and lowered the pH in the cultures of N. palea, thus enhancing the growth by 4%-20% during the whole growth period. High CO2-grown N. palea cells showed lower levels of dark respiration rates and higher I (k) values. Light-saturated photosynthetic rates and photosynthetic efficiencies decreased in N. palea with the doubling CO2 concentration in airflow to the bottom of cultures, although the doubling CO2 concentration in airflow to the surface cultures had few effects on these two photosynthetic parameters. N. palea cells were found to be capable of using HCO3 (-) in addition to gaseous CO2, and the CO2 enrichment decreased their affinity for HCO3 (-) and CO2. Although doubled CO2 level would enhance the biomass of N. palea and C. muelleri to different extents, compared with the marine diatom, it had a significant effect on the specific growth rates of N. palea. In addition, the responses of photosynthetic parameters of N. palea to doubled CO2 concentration were almost opposite to those of C. muelleri.

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In order to gain insight into the bloom sustainment of colonial Microcystis aeruginosa Katz., physiological characterizations were undertaken in this study. Compared with unicellular Microcystis, colonial Microcystis phenotypes exhibited a higher maximum photosynthetic rate (Pm), a higher maximum electron transfer rate (ETRmax), higher phycocyanin content, and a higher affinity for inorganic carbon (K-0.5 DIC <= 8.4 +/- 0.7 mu M) during the growth period monitored in this study. This suggests that photosynthetic efficiency is a dominant physiological adaptation found in colonial Microcystis, thus promoting bloom sustainment. In addition, the high content of soluble and total carbohydrates in colonial Microcystis suggests that this phenotype may possess a higher ability to tolerate enhanced stress conditions when compared to unicellular (noncolonial) phenotypes. Therefore, high photosynthetic activities and high tolerance abilities may explain the bloom sustainment of colonial Microcystis in eutrophic lakes.

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Algal size can affect the rate of metabolism and of growth. Different sized colonies of Nostoc sphaeroides were used with the aim of determining the effects of colony size on photosynthetic physiology and growth. Small colonies showed higher maximum photosynthetic rates per unit chlorophyll, higher light saturation point, and higher photosynthetic efficiency (a) than large colonies. Furthermore, small colonies had a higher affinity for DIC and higher DIC-saturated photosynthetic rates. In addition, small colonies showed higher photosynthetic rates from 5-45degreesC than large colonies. There was a greater decrease in Fv/Fm after exposure to high irradiance and less recovery in darkness for large colonies than for small colonies. Relative growth rate decreased with increasing colony size. Small colonies had less chl a and mass per unit surface area. The results indicate that small colonies can harvest light and acquire DIC more efficiently and have higher maximum photosynthetic rates and growth rates than large colonies.

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The growth and activity of photosynthetic CO2 uptake and extracellular carbonic anhydrase (CA(ext)) of the marine diatom Skeletonema costatum were investigated while cultured at different levels of CO2 in order to see its physiological response to different CO2 concentrations under either a low (30 mumol . m(-2) . s(-1)) or high (210 mumol . m(-2) . s(-1)) irradiance. The changes in CO2 concentrations (4-31 mumol/L) affected the growth and net photosynthesis to a greater extent under the low than under the high light regime. CAext was detected in the cells grown at 4 mumol/L CO2 but not at 31 and 12 mumol/L CO2, with its activity being about 2.5-fold higher at the high than at the low irradiance. Photosynthetic CO2 affinity (1/K-1/2(CO2)) of the cells decreased with increased CO2 concentrations in culture. The cells cultured under the high-light show significantly higher photosynthetic CO2 affinity than those grown at the low-light level. It is concluded that the regulations of CA(ext) activity and photosynthetic CO2 affinity are dependent not only on CO2 concentration but also on light availability, and that the development of higher CA(ext) activity and CO2 affinity under higher light level could sufficiently support the photosynthetic demand for CO2 even at low level of CO2.

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Microcystis aeruginosa Kutz. 7820 was cultured at 350 and 700 muL.L-1 CO2 to assess the impacts of doubled atmospheric CO2 concentration on this bloom-forming cyanobacterium. Doubling Of CO2 concentration in the airflow enhanced its growth by 52%-77%, with pH values decreased and dissolved inorganic carbon (DIC) increased in the medium. Photosynthetic efficiencies and dark respiratory rates expressed per unit chl a tended to increase with the doubling of CO2. However, saturating irradiances for photosynthesis and light-saturated photosynthetic rates normalized to cell number tended to decrease with the increase of DIC in the medium. Doubling of CO2 concentration in the airflow had less effect on DIC-saturated photosynthetic rates and apparent photosynthetic affinities for DIC. In the exponential phase, CO2 and HCO3- levels in the medium were higher than those required to saturate photosynthesis. Cultures with surface aeration were DIC limited in the stationary phase. The rate of CO2 dissolution into the liquid increased proportionally when CO2 in air was raised from 350 to 700 muL.L-1, thus increasing the availability of DIC in the medium and enhancing the rate of photosynthesis. Doubled CO2 could enhance CO2 dissolution, lower pH values, and influence the ionization fractions of various DIC species even when the photosynthesis was not DIC limited. Consequently, HCO3- concentrations in cultures were significantly higher than in controls, and the photosynthetic energy cost for the operation of CO2 concentrating mechanism might decrease.

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A mutant of Anabaena sp. strain PCC7120 requiring high CO2 was generated using Tn5 mutagenesis. This is the first data for a filamentous cyanobacterium. The mutant was capable of growing at 5% CO2, but incapable of growing at air levels of CO2. Southern hybridization analysis indicated that the Anabaena genome was inserted by the transposon at one site. The apparent photosynthetic affinity of the mutant to external dissolved inorganic carbon (DIC) was about 300 times lower that of the wild type (WT), and the medium alkalization rate as well as the carboxysomal carbonic anhydrase activity of the mutant was also lower than those of the WT. When the mutant was transferred from the culture medium bubbled with 5% CO2 to higher DIC (8.4% CO2) or 1% CO2, it showed similar responses to the WT. However, aberrant carboxysomes were found in the mutant cells through ultrastructural analysis, indicating it was most probably the wrong organization of the carboxysomes that eventually led to the inefficient operation of carboxysomal carbonic anhydrase and the subsequent defectiveness of the mutant in utilizing DIC.

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针对①中能反应中同位旋自由度是否达到平衡,②同位旋自由度对几中不同方法测量的核温度是否有影响 这两个基本问题,设计了用30和35MeV/u ~(36,40)Ar轰击~(112,124)Sn反应的实验方案。得到如下结果:对于前角5°处的耗散弹核碎裂产物,丰中子同位素与稳定核的产额比随产物出射动能的增加而减小,而丰质子子同位素与稳定核的产额比随动能的增加而增加,呈现明显的剪刀差分布特性。随耗散时间的增大,产物的平均中质比逐渐由弹核的平均中质比向系统的平均中质比过渡。这个结果说明在该反应中,同位旋自由度没有达到完全平衡。而对于20°处的DIC产物,上述剪刀差分布特性变得更不明显,这是同位旋自由度由非平衡向平衡过渡的表现。后角轻粒子的能谱分析表明,初始热核的同位旋会影响斜率核温度的提取,由于丰中子轻粒子~6He在~(40)Ar + ~(112)Sn系统中的蒸发被抑制,相比~(40)Ar + ~(112)Sn而言,其蒸发比较容易发生在衰变链早期,因此提取的温度偏高,同样,丰质子轻粒子~3He的温度在~(40)Ar + ~(112)Sn中略高。但中后角的同位素产额分析表明,反应系统的同位旋对双同位素比核温度几乎没有影响。核温度作为热核的热力学量,是独立于测量方法的,这种不同的方法得出的差异主要来源于同位旋对衰变机制的影响。作为一个尝试,将中高能反应中的熵的提取推广到这个能区,发现两个系统的熵几乎一致。在量子统计模型框架下,考察核温度与熵的关系发现,~(40)Ar + ~(112)Sn反应的挤出时刻密度略高于~(40)Ar + ~(112)Sn。

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本文主要研究了~(14)N+~(51)V(E_n = 94.6 MeV, 86.83 MeV, 79.2 MeV)的耗散碰撞,是上述系统性研究工作的一个重要组成部分。对N+~(51)V系统的DIC反应作了比较详细的研究,给出了类弹产物质心系维辛斯基图,不同出射道及不同TKEL下的角分布,以及不同TKEL不的电荷分布。从这些实验结果中提取全弛豫动能,相互作用时间,及电荷分布的一次矩,二次矩。讨论了~(14)N+~(51) 耗散碰撞随相互作用时间的推移的演化过程,定性分析了壳效应对N+V反应中电荷漂移的影响。同时还指出N+V反应中α集团效应的影响是不重要的,为~(16)O+~(27)Al 研究中提出的强α集团效应对其DIC过程有影响这一观点提供了旁证。最后提取了准弹截面,DIC截面,从而导出全熔合截面,讨论了DIC反应对轰击能的依赖关系

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把QMD模型扩展至10~100MeV/A能区,研究了该能区的重离子碰撞,并仔细检验了初始核在基态时传播的稳定性条件。~(40)Ca+~(40)Ca系统,在10 ~ 100MeV/A能区范围内研究了重离子反应机制随入射能量及碰撞参数的演化情况。我们发现,反应机制随能量的变化并不是突然的跃迁,而是一个连续的变化过程,不同的反应机制可以同时存在并发生竞争。在中心碰撞时,反应机制从全融合发展至非全融合,最后演化至碎裂机制。在周连碰撞时,随着入射能量的增加,根据我们提出的关于深部非弹碰撞和参加者-旁观者质量分布的判据,反应机制的可能变化趋势为从非完全融合或深部非弹碰撞到参加者-旁观者,最后发展至碎裂反应。我们知道,目前还没有人用QMD模型来研究过渡能区DIC机制的基本特征,我们还对~(20)(25Mev/A)+~(20)Ne系统周边碰撞时DIC机制的基本特征作了研究,计算结果表明:在中能区,DIC机制仍然存在,同时,在质量分布、旋转效应及能量损失方面具有低能时相同的特征,但与低能DIC的明显差别在于,出射的中间质量碎片已成为质量分布的主要部分,出射的轻粒子数目也相对增多。当碰撞参数小于7fm时,这里存在着不同反应机制的共存及竞争。根据质量分布随时间的演化情况,我们发现,中间质量碎片主要是由动力学过程中平均场涨落引起的动力学不稳定性造成的,统计衰变也贡献较小的一部分。由粗糙估计可以看出,25MeV/A时~(20)Ne+~(20)Ne系统的DIC机制仍然是一个趋向于平衡过程。相又于低能区,中能区的周边碰撞显得相当复杂

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本论文在解析了南黄海生态环境的基础上,首次研究揭示了浮游植物固碳强度的年际变化及生态反馈机制,获得了东中国近海浮游植物固碳强度及对海域源/汇格局的影响程度;同时,用室内模拟实验探讨了重金属和有机污染物胁迫下海水无机碳体系和源汇格局的变化过程,获得了一些新的认识。主要结论如下: 1. 南黄海浮游植物固碳强度具有明显的时空变化特征,与海域光照、流系和水团变化、海水磷的浓度等因素密切相关,并在一定程度上决定海区碳源/汇的性质。2005年秋季浮游植物日固碳量达9.5万吨,1983-2005年间,南黄海浮游植物固碳强度有降低的趋势,与海水关键营养盐-磷的限制有关。东中国近海浮游植物年总固碳量约为2.2亿吨,约占全球近海浮游植物的年固碳量的2.0%。 在综合分析秋季南黄海水文、化学、生物背景的基础上,系统阐明了海域浮游植物固碳体系的生物地球化学机制。结果表明,2005年秋季南黄海浮游植物固碳强度,即初级生产力变化在 97−701 mgC m-2 d-1之间,平均为307 mg C m-2 d-1;与其关系比较密切的环境因子为海水透明度、盐度、pH、氨氮 (NH4-N)、磷酸盐 (PO4-P) 以及Chl a。在这些因素中,PO4-P对初级生产力的影响最大,显然11月份南黄海的磷是浮游植物生长的限制因子,次之的影响因素是Chl a和NH4-N。 对南黄海源汇格局的研究发现,如果除去涌升流较为活跃的站位(A9、B7、B8、B9、C8、C9、 D9和A1),2005年秋季表层海水pCO2与浮游植物固碳强度明显负相关(r=-0.8,n=23, p<0.001)。在南黄海东部浮游植物固碳强度较高,pCO2值较低;而在西部海区浮游植物固碳强度较低的区域,其pCO2值较高。碳源/汇转折点浮游植物固碳强度为230 mgC m-2 d-1,即小于此值,海区为大气二氧化碳的源,反之为汇,并且CO2汇区浮游植物固碳强度平均值约是CO2源区的2倍多;浮游植物固碳作用,在某一时间和空间尺度内,基本决定了海区的源汇格局。估算结果显示,东中国近海浮游植物固碳量约为222×106t a-1,约为东中国近海通过海-气界面总表观碳汇强度每年1369万吨的16.2倍,仅就浮游植物的年固碳量而言,东中国近海约占全球近海浮游植物的年固碳量的2.0%。 研究揭示了近年来南黄海浮游植物固碳强度具有区域与年际变化明显这一显著特点。一般,近岸区(由黄海沿岸水和表层水控制)内,光照是浮游植物固碳的主要限制因子;从2001年后的大多数年份中,中央区(黄海冷水团控制)的浮游植物固碳强度均与磷酸盐浓度显著正相关,但与氮浓度的相关性不大,说明南黄海生态系统普遍存在着磷限制而非氮限制;混合区终年受黄、东海混合水控制,受到光照条件和营养盐浓度同时影响。根据本次观测所获数据,结合以前研究者的调查资料,我们发现从1983年到2005年,南黄海浮游植物优势种由Bacillariophyta变为Pyrrophyta,浮游植物细胞丰度和Chl a明显下降,浮游植物固碳强度几乎下降了二分之一 (由569.50 mgC m-2 d-1下降至306.83 mgC m-2 d-1),说明南黄海在世界边缘海固碳过程中的作用在降低。经过相关水质参数及生态环境变化的分析,以上现象是对关键营养盐磷的限制以及光限制响应的缘故。此外,研究还发现,由于南黄海初级生产者产量下降所引起的一些生态反馈信息,如浮游动物固碳量的下降和鱼类产量的锐减。 2. 室内模拟实验显示,重金属(铅、铜、镉和锌)及有机污染物(乙醇、丙酮、尿素和多灭磷)对水体生物固碳体系有重要影响,较低浓度时可提高水体的固碳能力,相应水体中的DIC、HCO3-和 Pco2 与对照组相比都明显下降 (P<0.01);当污染物达到一定浓度后,水体生物的固碳能力明显下降,其有机碳可降解转化为无机碳。当污染物小于转折浓度水体为大气二氧化碳的汇,反之为源。 水体固碳体系对于不同种类、不同浓度的污染物质所表现的受胁迫情况不同,低浓度各污染物(包括重金属和有机污染物)添加组中(对于重金属为0.1和1µmol•L-1,醇和酮分别为<0.5 mol L-1和<0.75 mol L-1),藻干重及固碳量均要大于初始值,说明适量的外源污染可能会促进藻类生长,提高水体的固碳能力,相应水体中的DIC、HCO3- 和PCO2与对照组相比都明显下降 (P<0.01)。当污染物达到一定浓度后,由于其毒害作用,使得水体内生物的固碳能力下降,甚至分解并转化为无机碳,从会引起DIC、HCO3- 和PCO2含量的升高,其含量上升幅度会因固碳体系对不同种类污染物耐受程度的差异而不同。对于尿素和多灭磷,二者浓度分别达到80和20mgL-1时,水体中二氧化碳各参数仍呈现下降趋势,说明在该浓度范围内,大型藻类(如石莼)仍可利用添加物中的氮和磷,将其做为氮源或磷源,促进水体总固碳量的增加。 污染物胁迫对水体碳源汇能力及格局可起到一定的调控作用,与污染物的浓度密切相关,污染物存在着一转折浓度,分别为5µmol L-1(铜)、20µmol L-1(镉) 0.75mol L-1(酮),当污染物添加小于转折浓度并排除其他影响因素时,水体表现为大气CO2的汇,并且适量的增加污染物浓度会使海洋碳汇能力有所增强;而当污染物超出转折浓度时,水体成为CO2的源,其CO2的释放量是随着污染物浓度的增加而增大。对与研究中其他种类的污染物,在实验室设计范围内,水体始终表现为大气CO2的汇。

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本文采用碳稳定同位素比分析法,进行了29个调查站的溶解无机碳稳定同位素的研究。研究结果表明,海水的混合强度是决定#delta#~13C-DIC分布的重要因素;在表层海水中,海-气界面二氧化碳交换和浮游植物光合作用对#delta#~13C-DIC影响较大;在中、底层海水,特别是底层海水中,有机物的氧化分解作用对#delta#~13C-DIC影响较大。

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过量氮和磷引起的海水富营养化引起了一系列的生态环境效应,探讨二者的耦合关系对阐明全球海洋生态环境变化机制意义重大。本论文首次探讨了过量氮和磷引起的富营养化对海水无机碳体系的影响,通过室内系统模拟实验,构筑了过量氮和磷与无机碳体系变化的定量耦合关系,在此基础上获得了中国近海典型海域特别是南黄海近十年氮和磷演变引起的无机碳源汇格局变化,获得了以下一系列新的结果和认识: 1、不同营养盐(NO3-、NH4+、NO2-和PO43-)对水体溶解无机碳体系均有重要影响,且影响程度有较大的差异。 在模拟实验中,当NO3-<188 μmol/L,NH4+<126 μmol/L,NO2-<39.5 μmol/L时均可明显提高水体的固碳能力,相应水体中的DIC、HCO3-和 pCO2均较空白对照组时有一定程度的下降。当N浓度达到一定值后,其固碳能力减弱,DIC、HCO3-和pCO2出现相反变化。当NH4+>126 μmol/L和NO2->39.5 μmol/L时pCO2增加,向大气释放CO2。在PO43-添加组中,当浓度小于19.5μmol/L时DIC、pCO2较空白对照组下降,水体表现为大气CO2的汇,其固碳能力高于N组。在孔石莼添加组中,各营养盐组水体的固碳能力均高于空白对照组,相应水体中DIC、HCO3-和pCO2的下降明显。其中,同一营养盐浓度水平下,NH4+组中各无机碳组分的变化幅度明显高于NO3-和NO2-组,PO43-组的无机碳体系变化幅度低于N组。其中,当NO3-、NH4+和NO2-浓度分别在71 μmol/L,49.7 μmol/L和11.7 μmol/L时,pCO2下降明显,水体表现为大气CO2的强汇。对无机碳各参数的变化量与营养盐进行多元回归分析,得到以下统计关系: ⊿DIC=-0.937(⊿PO43-)-0.34(⊿NO3-)-0.46(⊿NH4+)+0.11(⊿NO2-)(R2=0.69, n=30,Sig.<0.05) ⊿HCO3-=-1.357(⊿PO43-)-0.35(⊿NO3-)-0.57(⊿NH4+)-0.013(⊿NO2-)(R2=0.76, n=32, Sig.<0.05) ⊿CO32-=0.344(⊿PO43-)+0.16(⊿NO3-)+0.18(⊿NH4+)+0.076(⊿NO2-)(R2=0.69, n=32, Sig.<0.05) ⊿pCO2=-1.321(⊿PO43-)-0.12(⊿NO3-)-0.31(⊿NH4+)-0.032(⊿NO2-)(R2=0.84, n=35, Sig.<0.01) 2.氮、磷对海水无机碳体系的源汇格局影响主要受控于水体浮游藻类对营养盐的利用。 模拟实验各种情况下Chl-a的浓度均有不同程度的变化。在N组中,当NH4+<126 μmol/L,随着NH4+浓度的增加,Chl-a浓度增加,而高浓度(NH4+>126 μmol/L)的实验组中,Chl-a则随浓度的增加而下降。当NO2-和PO43-的浓度分别大于39.5 μmol/L和19.5 μmol/L时,水体中Chl-a随营养盐浓度的增加而出现下降趋势,不同的是NO3-添加组在实验浓度范围内藻类均出现了不同程度的增长,这可能与浮游藻类对过量营养盐的耐受性不同有关。在低浓度时,PO43-组pCO2的下降最为明显,这与 PO43-组Chl-a的含量较高相一致,其次为NH4+,NO3-高于NO2-,可见在实验水体中PO43-对于藻类新陈代谢作用影响明显,从而作用到无机碳上的影响也就最为明显。对各实验水体⊿Chl-a与无机碳各组分作相关性分析发现,⊿Chl-a与⊿pCO2的相关性最为明显(R2=0.75,p<0.0001),这可能是因为浮游藻类光合作用和分解作用消耗或生成的首先是海水中的游离CO2(即pCO2)。在孔石莼组中,由于大藻对过量营养盐的耐受性较强,因此各组中藻类干重均有一定程度的增长。藻类干重的增加以NH4+最为明显,其次为NO3-和NO2-,这可能与其对N盐的优先吸收顺序NH4+>NO3->NO2-有关。加PO43-组中藻类的干重增加量低于NH4+和NO3-组,这与大藻的生理特性有关。对藻类干重增加量⊿m与⊿DIC作相关性发现,二者相关性明显(R2=0.64,p<0.01),这是由于孔石莼光合作用同时吸收HCO3-和CO2为碳源有关。 3、近年来,中国近海由于海水过量氮磷引起的富营养化,可使大部分海域海水无机碳汇强度增加 应用室内模拟获得的无机碳与氮、磷之间的定量耦合关系,估算了过量氮、磷引起的富营养化条件下,中国近海水体无机碳源汇的变化情况。结果表明,近十年来,由于氮、磷浓度的增加而导致渤海、南黄海、北黄海和东海每年从大气中多吸收0.197×106t C、0.302×106t C、0.039×106t C和2.233×106t C,东中国近海营养要素的含量的变化及组成比例的时间性和地区性差异是造成各海区碳通量差异的重要因素;对2006年南黄海水文、化学、生物与无机碳体系之间的相互关系进行综合分析,可知水体无机碳体系与营养盐水平密切相关。