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南沙群岛海域理化参数垂向分布特征及跃层生态系的提法 总被引：4，自引：2，他引：4
自1985～1999年中国科学院南沙综合科学考察队在南沙群岛进行了12个航次的综合科学考察.根据调查的结果,通过分析南沙群岛海域理化参数垂向分布特征,得出次表层海水理化参数具有极值现象、跃变现象和波动现象的特点,讨论了这些独特特征反映的独特生境,提出了南沙群岛海域垂直方向上存在跃层生态系的观点. 相似文献
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2006年夏季珠江冲淡水驱动的上升流 总被引：2，自引：1，他引：1
根据珠江口及其附近海域2006年夏季（7-8月）航次水文调查资料，发现调查期间，除了西南季风驱动下的冲淡水东向扩散外，粤西珠江口外冲淡水主要呈西向扩散趋势，并且西向扩散的冲淡水下存在上升流。已有的模型研究中，西南季风下珠江口外没有出现上升流，说明西南季风不是珠江口外上升流产生的主导因素。观测的温盐分布、潜标流速时间序列与走航ADCP流态表明，上升流产生的原因是:（1）口门外冲淡水南向扩展驱动了垂向重力环流；（2）密度跃层以下东北向沿岸流的底边界层Ekman效应；（3）口门外冲淡水团之间的气旋型中尺度涡旋作用。 相似文献
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《热带海洋学报》2005,24(6):I0001-I0005
第1期研究论文末次冰期以来西太平洋暖池变化的浮游有孔虫记录…………………涂霞,郑范,向荣,陈木宏,汤贤赞,颜文(1)南沙群岛海域沉积物稀土元素地球化学研究……………………………………………田正隆,戴英,龙爱民,陈绍勇(8)珠江口不同沉积有机质的来源及相对含量………………………………………胡建芳,彭平安,麦碧娴,张干,殷克东(15)珠江口柱状沉积物中磷的分布特征及其环境意义…………………………………………………………岳维忠,黄小平(21)夏季季风转换期间南沙群岛海域的温盐分布特征………………………………………毛庆文,王卫强,齐… 相似文献
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南沙群岛海域次表层溶解氧垂直分布最大值的强度特征 总被引：3，自引：0，他引：3
分析了“八五”、“九五”国家科技专项南沙群岛海域综合科学考察的现场调查资料,对南沙群岛海域次表层存在的溶解氧垂直分布最大值现象提出了定量表征其强度的方法,并依此法对溶解氧垂直分布最大值强度的特征、季节变化、区域分布等进行了分析。结果表明,南沙群岛海域海水中的溶解氧垂直分布最大值强度在不同的海区、不同的季节表现不同。南沙群岛海区四季均有明显的溶解氧最大值现象出现,就平均值而言,春、夏、冬季次表层溶解氧垂直分布最大值现象较为明显,秋季相对较弱;春季溶解氧垂直分布最大值强度的高值出现在西南部海区和北部的珊瑚礁区,与季风过渡期海水溶解氧主要受生物作用相对应;冬、夏季较高的溶解氧垂直分布最大强度值分别出现在西北部和西部,对应于季风盛行时期的南沙西部沿岸流;夏季出现在东部和南部的低值区又与南沙群岛海区西南季风时期出现的南沙逆流相对应。定量表征的结果与该海区调查研究的分析结果相符合,同时又较好地反映了该海域在季风作用下的物理和生物过程。 相似文献
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东海西部沿岸海域冬季的逆温跃层现象及其与环流的关系 总被引：1，自引：0，他引：1
本文引用《渤海、黄海、东海海洋图集──水文》分册（１９９２）中有关逆温跃层分布变化的图幅以及温盐历史资料,指出东海西部沿岸（２２～３２°Ｎ）冬季出现逆温跃层的区域北起长江口,南到南澳岛以南几乎相联成片的现象,论述了这一分布与中国东南近海冬季潜伏于深底层的暖流水的区域相吻合,从而从水文结构上证实了冬季在深底层粤东沿岸的南海暖流北上通过台湾海峡西部与闽浙沿岸的台湾暖流相接这一环流特征。 相似文献
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1994年9月南沙群岛调查海区的跃层特征 总被引：5，自引：1，他引：5
对１９９４年９月南沙群岛海区综合考察的标准层资料，运用垂向梯度法，计算了调查海区温、盐及密度３种跃层所处的深度及各自的厚度和强度，并进行了相应的分析。文章还讨论了调查海区温、盐和密度的垂向最大梯度的分布。分析表明，调查海区同时存在着３种跃层现象，多跃层现象较普遍，温、盐和密度的垂向最大梯度所在深度较小。 相似文献
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根据珠江口外沿岸海域2006年夏季(7-8月)及冬季(2006年12月-2007年1月)航次的CTD调查资料,分析了调查海域夏季与冬季的温度、盐度分布,温度、盐度、密度跃层特征及其与上升流、中尺度涡旋和海流的关系.结果表明:1)夏季调查海域冲淡水扩展、上升流、中尺度涡等现象在温度、盐度分布中都有很明显的表征,并对跃层分布有显著的影响,形成了复杂的跃层类型;在冲淡水扩展的影响下,还形成了双跃层与障碍层现象.2)冬季海水混合剧烈,沿岸浅水区域跃层现象不明显,在陆坡深水区存在跃层现象. 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-F0003
<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, 相似文献
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The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
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The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献
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Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(3):237-250
Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions. 相似文献
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Vance P. Vicente 《Marine Ecology》1989,10(2):179-191
Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned. 相似文献