赤道西太平洋末次盛冰期以来的浮游有孔虫氧碳稳定同位素记录

对西太平洋暖池核心区MD01—2386柱状样最上部5m进行了高分辨率的浮游有孔虫Globigerinoides ruber和Pulleniatina obliquiloculata的氧、碳稳定同位素分析,结合AMS^14C测年,研究表明其属于末次盛冰期-全新世的沉积。赤道西太平洋海区末次盛冰期以来δ^18O值显著降低,但有几次回返事件。表层浮游有孔虫G．ruber比次表层温跃层属种P．obliquiloculata对于环境变化的响应要快,但后者变化的幅度较大。这两个种的氧、碳同位素差值反映出温跃层深度自末次盛冰期以来逐渐加深,并存在周期性的回返事件,说明西太平洋暖池晚第四纪冰期旋回存在气候不稳定性。     

西太平洋边缘MIS6期以来钙质超微化石的氧同位素记录及其古海洋学意义

对西太平洋边缘不同纬度带的WP7、Ph05-5和Z14-63个柱状岩心进行了超微化石氧同位素分析。结果表明,MIS6期以来这3个岩心中超微化石δ18O值都呈现明显的冰期-间冰期旋回变化特征,冰期δ18O平均值重于间冰期(Z14-6岩心倒数第二次冰期旋回除外),这与冰期时表层海水温度低于间冰期相对应。MIS6—1期超微化石δ18O平均值从WP7岩心到Ph05-5岩心再到Z14-6岩心依次变重,对应于3个岩心所在海区位置年平均SST依次降低。同一岩心样品中浮游有孔虫温跃层种Neogloboquadrina dutertrei δ18O平均值重于超微化石δ18O平均值,这与超微化石和浮游有孔虫N.dutertrei δ18O值各自所代表的不同水层温度特征相吻合。MIS6期以来从WP7岩心到Ph05-5岩心再到Z14-6岩心,超微化石与浮游有孔虫N.dutertrei δ18O平均值之间的差值越来越小,这与3个岩心所在位置上部水体扰动越来越强对应。WP7和Ph05-5两个岩心中超微化石和浮游有孔虫N.du-tertrei氧同位素差值与超微化石下透光带属种Florisphaera profunda百分含量变化特征共同表明MIS6期以来西太平洋暖池核心区和西菲律宾海黑潮源区的温跃层间冰期比冰期深。     

冲绳海槽南部两万年来的浮游有孔虫与古海洋学事件

冲绳海槽南部92-255和92-170两柱状样岩心的浮游有孔虫定量分析及其组合的变化、游浮与底栖有孔虫壳体δ18O测定和AMS14C测年资料,提供了末次冰期以来重要的古海洋学记录。浮游有孔虫的转换函数计算表明,海槽区末次冰期表层水温下降值及末次冰期的季节温差均比西太平洋开放海区相应纬度大,反映了边缘海对冰期-间冰期旋回中气候变化的放大效应,冰期-冰后期的对比还体现在由浮游有孔虫属种组合所反映的水团和水体垂直结构的变化上;末次冰消期古温度变化及浮游有孔虫δ18O变化记录了一次短暂的气候回返(10170～9170aBP);详细的地层分析还揭示了中全新世的一次Pulleniatina obliquiloculata含量低谷。     

南海南部水体和沉积物中的浮游有孔虫氧碳同位素分析

通过对2002年南海南部春季水体和表层沉积物中浮游有孔虫的δ^18O和δ^13C分析,初步探讨该区有孔虫氧碳同位素的海洋环境指示意义及其与沉降过程的关系。结果表明,南海南部春季表层水体中Gltbigerinoides ruber （G．ruber）与Globigerinoides sacculifer（G．sacculifer）的δ^18O均值基本相似,相对它们在表层沉积物中的δ^18O明显要小;但在表层沉积物中G．ruber的δ^18O则比G．sacculifer相对要小0．34‰。这种差异可能与G．sacculifer的配子生殖二次钙化以及2个种属的季节性差异有关。Pulleniatinaobliquiloculata（P．obliquiloculata）的δ^18O在沉积物和水体中均较G．ruber和G．sacculifer明显偏大,表现出较大的种间差异。P．obliquiloculata的δ^18O在春季水体中比其在沉积物中平均约小0．7‰,差值较大,可能是因为P．obliquiloculata为冬季种,主要出现在冬季低温水体中。3种浮游有孔虫的δ^13C以G．sacculifer最大,G．ruber次之,P．obliquiloculata最低,这种差异可能主要由属种间的生命效应所引起。表层沉积物中G．ruber和G．sacculifer的δ^18O从区域的西北往东南有逐渐变小的趋势,可能受区域年均表层水温西北低东南高的影响。在上升流发育区,P．obliquiloculata的δ^18O和δ^13C均明显偏高,其δ^13C与水体营养的关系与南海北部的明显相反,有待进一步深入研究。     

近190ka B.P.以来西太平洋暖池北缘上层海水结构和古生产力演化特征及其控制因素——来自钙质超微化石、有孔虫和同位素的证据

对取自西菲律宾海暖池北缘的Ph05—5岩芯进行了钙质超微化石和有孔虫研究。在利用氧同位素曲线对比和AMS^14C数据进行地层划分的基础上,依据超微化石和有孔虫及其同位素组成等指标,分析了近190 ka B．P以来区域生产力和上层海水结构的演变特征,探讨了其控制因素和所指示的古海洋学意义。钙质超微化石下透光带属种Florisphaera profunda百分含量和基于浮游有孔虫转换函数的温跃层深度变化表明,Ph05—5岩芯所在的热带西太平洋暖池北缘约190kaB．P．以来,营养跃层和温跃层冰期（MIS 6期和5d-2期）浅,间冰期（MIS5e）和全新世深,而MIS5e期是最近两个冰期旋回中营养跃层和温跃层深度最深时期。通过Fprofunda百分含量初级生产力转换方程计算结果和与钙质超微化石绝对丰度的变化显示,冰期初级生产力高,间冰期和全新世初级生产力低,MIS5e期初级生产力为末两次冰期旋回之最低。此外,Ph05—5岩芯△δ^13Cc.wullerstorfi-coccolith和△6δ^12Cc.wullerstorfi-N.dutertrei.差值变化显示,190ka B．P以来表层输出生产力冰期高,间冰期低,其中最为突出的特征也是MIS5e期为生产力输出的最低值期。上层海水结构和生产力的上述变化特征与现代La Nina事件暴发时的海洋环境相当类似,该海区MIS5e期可能是LaNina事件频繁爆发的一段时期,可以与现代LaNina现象类比。同时,根据Wyrtki提出的信风张弛理论推测MIS5e期,由于LaNina事件的频繁暴发黑潮主流应该是增强的。     

南海北部盛冰期以来古海洋环境变化的沉积记录

利用气候替代指标U₃₇k-SST,浮游有孔虫Globigerinoides ruber的δ18O,δ13C,微体古生物种群变化、陆源和生源组分以及沉积物粒径等,对南海北部69孔沉积物进行综合研究.结果表明U₃₇k-SST在冰后期为23.3～26.9℃,在末次盛冰期时为22.2～23.8℃.用浮游有孔虫转换函数法对季节温差进行估算,在冰后期为4.5～7.0℃,在末次冰期为7.0～9.0℃,两种估温法均反映了古气候变化相应的海水表层温度.69柱沉积物地层记录在末次盛冰期浮游有孔虫温带优势种Neogloboguadrina pachyderma和营养种Neogloboguadrina dutertrei丰度一致增加;热带优势种Pulleniatina obliqueloculata和Globigerinoide sacculifer以及超微化石丰度则相应减少,而冰后期则相反.浮游有孔虫、钙质超微化石组成和数量的改变也为古海洋温度升、降提供了直接的证据.研究还表明南海北部冰后期以河流搬运为主,末次盛冰期时以风力搬运占优势,这反映了冬季风强化.     

中更新世气候转型期西太平洋暖池的表层海水温度和氧同位素变化

通过对大洋钻探(ODP)第130航次807站A孔井深12.54～16.38m沉积物中浮游和底栖有孔虫的稳定同位素δ18 O以及浮游有孔虫壳体的Mg/Ca测试,揭示了中更新世气候转型期(800～1 000kaBP)西太平洋暖池表层海水温度和氧同位素的变化。研究发现,中更新世时期ODP 807站的表层海水温度在25.1～30.9℃之间浮动,平均为28.4℃,接近现代暖池区实测温度值,冰期/间冰期之间的温度差值在1.5～5℃左右,与晚第四纪时的温差相近;同时,表层海水温度和底栖有孔虫氧同位素呈现同步变化的趋势,没有明显的超前或滞后的相位关系,区别于前人在暖池区的研究结果。间冰期时,表层海水温度上升伴随着温跃层变深、盐度降低,与现代西太平洋暖池La Ni珘na状态类似;冰期时则类似于El Ni珘no状态。中更新世气候转型期,西太平洋暖池的表层海水温度、温跃层深度变化受低纬热带驱动影响,都显示出强烈的岁差周期(16.8ka),而底层水氧同位素更多受到高纬的影响。     

冲绳海槽南部末次间冰期以来古海洋学变迁：ODPI202站的记录

对冲绳海槽南部ODP1202站165个沉积物样品进行了CaCO3含量测定和47个样品以浮游有孔虫为主的微体化石定量分析。应用CaCO3含量变化与δ^18曲线的对应关系，初步将1202站岩心划分为MIS 1—5期的沉积。根据浮游有孔虫中暖水、凉水、浅水和深水等生态组合丰度变化，推测冲绳海槽南部晚更新世末次间冰期以来，温跃层呈逐步加深和表层海水温度逐渐升高的趋势。MIS5期以较浅温跃层和较低表层海水温度为特征，推测与研究区末次问冰期存在上升流有关。末次冰期(MIS4～2期)时，Pulleniatina obliquiloculata在整个冲绳海槽中普遍以低丰度值出现，标志黑潮主流轴可能迁移出冲绳海槽。     

南海西沙海槽83PC柱状沉积物组成特征及其古环境意义

为了解南海北部末次间冰期以来的沉积环境演化,分析了西沙海槽83PC柱状沉积物的浮游有孔虫氧碳同位素、碳酸钙、有机碳和粒度组成。浮游有孔虫的δ18 O值具有冰期-间冰期旋回特征,记录了海平面的升降和古气候的变化,而海平面变化控制了沉积物的碳酸钙和有机碳含量。冰期,海平面下降,陆源物质输入增多,带来了大量的碎屑物质和陆源有机质,沉积物具有低碳酸钙含量和高有机碳含量;间冰期,海平面上升,陆源物质输入减少,碎屑物质的稀释作用减弱,沉积物具有高碳酸钙含量和低有机碳含量。南海北部83PC柱状沉积物记录了末次间冰期以来的多次海平面升降旋回,还记录了气候变冷事件以及低碳酸钙沉积事件,其中,150、510、660和740cm处的低碳酸钙含量和相对重δ18 O值记录了全球性气候变冷事件,而冰后期的低碳酸钙沉积事件,则主要反映了季风降雨的增强,出现了洪水高发期,陆源碎屑物质对碳酸钙沉积的稀释作用明显增强。     

北大西洋45°N区氧同位素3期以来上层水体性质的变化

北大西洋45°N区是北大西洋冰筏碎屑(IRD)带的中心区,其海洋沉积物包含高分辨率沉积环境和气候变化信息,对45°N区沉积记录的研究有利于反演末次冰期以来古海洋环境的变化.通过对岩心Hu71-377中IRD含量的统计、浮游有孔虫组合及氧和碳同位素(δ18O和δ13C)分析,重建了北大西洋45°N上层水体水团性质演化历史...     

Microbial Biomass and Organic Nutrients in the Deep-Sea Sediments of the Central Indian Ocean Basin

In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.     

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations.     

Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans

A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Evaluation of the Risk of Marine Slope Instability: A Pseudo-3D Approach for Application to Large Areas

This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed.