Submarine canyons on the north of Chiwei Island: influenced by recent extension of the southern Okinawa Trough          下载免费PDF全文

ZHAO Yuexi  LIU Baohu  LI Xishuang  LIU Chenguang  WU Jinlong  WANG Kuiyang 《海洋学报(英文版)》2008,27(4):63-72

Based on new multibeam bathymetric data and about 300 km long single seismic profiles, three topographic units were identified:the canyons, fractural valley and submarine terrace on the north of Chiwei Island where is a structural transition zone between the southern trough and the middle trough. The Chiwei Canyon and the North Chiwei Canyon are two of the largest canyons in the East China Sea (ECS) slope. Topographic features and architectures of them are described. The study shows that both of them are originated along faults. The evolution and spatial distribution of topographic units in the study area are controlled mainly by three groups of faults which were formed and reactive in the recent extensional phase of Okinawa Trough. The Chiwei Canyon was initiated during the middle Pleistocene and guided by F4 that is a N-S trending fault on the slope and F1, a large NW-SE trending fault on the trough. The pathway migration from the remnant channel to the present one of Chiwei Canyon is the result of uplift of tilted fault block that is coupled to the recent extension movements of the southern trough. The submarine terrace is detached from the ECS slope by the NEE-trending fault. The North Chiwei Canyon, developing during the late Pleistocene, is guided by F5, a N-S trending fault, diverted and blocked by the submarine terrace.  相似文献   

Differential physiological responses of the coastal cyanobacterium <Emphasis Type="Italic">Synechococcus</Emphasis> sp. PCC7002 to elevated <Emphasis Type="Italic">p</Emphasis>CO<Subscript>2</Subscript> at lag,exponential, and stationary growth phases     

Shanli Mou  Gang Li  Hongmei Li  Fazhong Li  Zhisheng Shao  Jinsong Li  Changfeng Qu  Yongyu Zhang 《中国科学:地球科学(英文版)》2018,61(10):1397-1405

We studied the effects of expected end-of-the-century pCO₂ (1000 ppm) on the photosynthetic performance of a coastal marine cyanobacterium Synechococcus sp. PCC7002 during the lag, exponential, and stationary growth phases. Elevated pCO₂ significantly stimulated growth, and enhanced the maximum cell density during the stationary phase. Under ambient pCO₂ conditions, the lag phase lasted for 6 days, while elevated pCO₂ shortened the lag phase to two days and extended the exponential phase by four days. The elevated pCO₂ increased photosynthesis levels during the lag and exponential phases, but reduced them during the stationary phase. Moreover, the elevated pCO₂ reduced the saturated growth light (Ik) and increased the light utilization efficiency (α) during the exponential and stationary phases, and elevated the phycobilisome:chlorophyll a (Chl a) ratio. Furthermore, the elevated pCO₂ reduced the particulate organic carbon (POC):Chl a and particulate organic nitrogen (PON):Chl a ratios during the lag and stationary phases, but enhanced them during the exponential phase. Overall, Synechococcus showed differential physiological responses to elevated pCO₂ during different growth phases, thus providing insight into previous studies that focused on only the exponential phase, which may have biased the results relative to the effects of elevated pCO₂ in ecology or aquaculture.  相似文献   

<Superscript>230</Superscript>Th/<Superscript>238</Superscript>U dating of hydrothermal sulfides from Duanqiao hydrothermal field,Southwest Indian Ridge     

Weifang Yang  Chunhui Tao  Huaiming Li  Jin Liang  Shili Liao  Jiangping Long  Zhibang Ma  Lisheng Wang 《Marine Geophysical Researches》2017,38(1-2):71-83

Duanqiao hydrothermal field is located between the Indomed and Gallieni fracture zones at the central volcano, at 50°28′E in the ultraslow-spreading Southwest Indian Ridge (SWIR). Twenty-eight subsamples from a relict chimney and massive sulfides were dated using the ²³⁰Th/²³⁸U method. Four main episodes of hydrothermal activity were determined according to the restricted results: 68.9–84.3, 43.9–48.4, 25.3–34.8, and 0.7–17.3 kyrs. Hydrothermal activity of Duanqiao probably started about 84.3 (±0.5) kyrs ago and ceased about 0.737 (±0.023) kyrs ago. The periodic character of hydrothermal activity may be related to the heat source provided by the interaction of local magmatism and tectonism. The estimated mean growth rate of the sulfide chimney is <0.02 mm/yr. This study is the first to estimate the growth rate of chimneys in the SWIR. The maximum age of the relict chimney in Duanqiao hydrothermal filed is close to that of the chimneys from Mt. Jourdanne (70 kyrs). The hydrothermal activity in Dragon Flag field is much more recent than that of Duanqiao or Mt. Jourdanne fields. The massive sulfides are younger than the sulfides from other hydrothermal fields such as Rainbow, Sonne and Ashadze-2. The preliminarily estimated reserves of sulfide ores of Duanqiao are approximately 0.5–2.9 million tons.  相似文献   

Crustal structure of the Southwest Subbasin,South China Sea,from wide-angle seismic tomography and seismic reflection imaging     

Zhiteng?YuEmail author  Jiabiao?LiEmail author  Weiwei?Ding  Jie?Zhang  Aiguo?Ruan  Xiongwei?Niu 《Marine Geophysical Researches》2017,38(1-2):85-104

The Southwest Subbasin (SWSB) is an abyssal subbasin in the South China Sea (SCS), with many debates on its neotectonic process and crustal structure. Using two-dimensional seismic tomography in the SWSB, we derived a detailed P-wave velocity model of the basin area and the northern margin. The entire profile is approximately 311-km-long and consists of twelve oceanic bottom seismometers (OBSs). The average thickness of the crust beneath the basin is 5.3 km, and the Moho interface is relatively flat (10–12 km). No high velocity bodies are observed, and only two thin high-velocity structures (~7.3 km/s) in the layer 3 are identified beneath the northern continent-ocean transition (COT) and the extinct spreading center. By analyzing the P-wave velocity model, we believe that the crust of the basin is a typical oceanic crust. Combined with the high resolution multi-channel seismic profile (MCS), we conclude that the profile shows asymmetric structural characteristics in the basin area. The continental margin also shows asymmetric crust between the north and south sides, which may be related to the large scale detachment fault that has developed in the southern margin. The magma supply decreased as the expansion of the SWSB from the east to the west.  相似文献   

Residues,sources and tissue distributions of organochlorine pesticides in dog sharks (Mustelus griseus) from Zhoushan Fishing Ground,China     

Shanshan Zhou  Lu Tong  Qiaozhi Tang  Xiaoting Gu  Bin Xue  Weiping Liu 《Marine pollution bulletin》2013

Ten dog sharks (Mustelus griseus) collected from Zhoushan Fishing Ground, China, were analysed for organochlorine pesticides in various tissues, including muscle, liver, skin, gill and fin, with the aim to study the residues, sources and tissue distributions of these chemicals in high trophic level marine fishes. The concentrations of DDTs, HCHs, and chlordanes varied from 7.27–26.62, 2.67–3.35, and 0.54–0.61 ng/g wet weight, respectively, with the estimated daily intake far below the acceptable daily intake and Chinese edible hygienic criteria. Data from the tissue distribution suggested a tendency of DDTs and chlordanes to accumulate in the liver, but for HCHs, direct gill penetration may be an important means of entrance. In addition, the compositional profiles indicated that the residues of HCHs and chlordanes mainly originated from the historical usage of these chemicals. However, the predominant maternal compounds and the o,p′-DDT/p,p′-DDT ratios reflected a recent use of dicofol.  相似文献   

An ensemble estimation of impact times and strength of Fukushima nuclear pollution to the east coast of China and the west coast of America     

HAN GuiJun  LI Wei  FU HongLi  ZHANG XueFeng  WANG XiDong  WU XinRong  ZHANG LianXin 《中国科学:地球科学(英文版)》2013,(8):1447-1451

Based on the statistics of all surface drifting buoys of 1978-2011 and Lagrangian tracers simulated from high quality ocean reanalysis currents,the impact times and strength of Fukushima nuclear pollution to the east coast of China and the west coast of America have been estimated.Under the circumstances of the radioactive pollutants drifting in the ocean surface,preliminary research results show that while the tracers took about 4 years to reach the west coast of USA,there are two types of tracers to carry out Fukushima nuclear pollutants to reach the east coast of China,corresponding to 1.5-year recirculation gyre transport and 3.5-year subtropical circulation transport.The distributions of the impact strength at these time scales are given according to the variation of relative number concentration with time combined with the decaying rate of radioactive matter.For example,starting from 1% at 1.5-year,of the initial level at the originating area of Fukushima nuclear pollution,the impact strength of Cesium-137 in the South China Sea continuously increases up to 3% by 4 years,while the impact strength of Cesium-137 in the west coast of America is as high as 4% due to the role of strong Kuroshio-extension currents as a major transport mechanism of nuclear pollutants for that area.  相似文献   

长江口及邻近海域现代沉积速率及其对长江入海泥沙去向的指示意义   总被引：1，自引：0，他引：1  

王昕  石学法  王国庆  乔淑卿  刘涛 《地球科学》2013,38(4):763-775

对长江口及附近海域的16根重力柱样进行了210Pb沉积速率测试,结合以往成果,揭示了该区现代沉积速率分布格局,对其控制因素以及其对认识长江入海泥沙去向的指示意义进行了探讨.沉积速率最高值分布在南支口外、杭州湾口群岛北部的前三角洲地区,最高可达6.3m/a,总体上在3cm/a以上;次高值分布在杭州湾北部,约1.7～3.0cm/a,南部略低,约0.4～1.0cm/a;长江口水下负地形北部海域存在小片沉积速率较高的区域,最高值达2.58cm/a;低值主要分布在苏北辐射沙洲、过渡沉积区以及浅海陆架的大片区域,基本保持在1cm/a以下.研究表明,长江泥沙出口门后主要在水下三角洲地区进行了堆积,其次有相当部分在涨潮流顶托下进入杭州湾,进入杭州湾南部的泥沙又在落潮流作用下经杭州湾南侧向舟山海域方向输运;长江入海物质向外海的扩散基本被控制在123°E以西,苏北辐射沙洲、过渡沉积区以及浅海陆架的大片区域缺乏现代长江物质供应;长江悬浮泥沙对研究区东北部陆架区影响较小,废黄河口被侵蚀物质和黄海悬浮物质为其较高沉积速率的主要贡献者.  相似文献   

Hydrography and Circulation in the Eastern Tropical Indian Ocean during April-May 2011   总被引：2，自引：0，他引：2       下载免费PDF全文

XUAN Li-Li  QIU Yun  XU Jin-Dian  HE Yun-Kai 《大气和海洋科学快报》2012,5(4):284-289

The distribution of hydrography and circulation in the eastern tropical Indian Ocean(ETIO) during April-May 2011 were analyzed using cruise observations,satellite observations,and historic hydrographic data.It was observed that warm water(28℃) occupies the upper 50-m layer in the ETIO.Low-salinity surface water was observed at the mouth of the Bay of Bengal(BOB),which further extends to the Arabian Sea and off Sumatra via the Sri Lanka coast and the eastern bay mouth.Arabian Sea high-salinity water(ASHSW) is carried eastward along the equator to around 90°E by the equatorial undercurrent(EUC).It also runs south of Sri Lanka(north to 3°N) and in the western bay mouth(west to 87°E) but is much shallower than its counterpart at the equator.It is suggested to be the residual of the ASHSW,which intrudes into the BOB during the preceding southwest monsoon.Our results also show that,in the south of Sri Lanka,just below this subsurface high-salinity water,very-low-salinity water(about 34.8) occurs at depths of 100-200 m.Further analysis suggests that this low-salinity water comes from the BOB.  相似文献   

Analysis of multi-dimensional SAR for determining the thickness of thin sea ice in the Bohai Sea   总被引：1，自引：0，他引：1  

张晰  张杰  孟俊敏  苏腾飞 《中国海洋湖沼学报》2013,31(3):681-698

Flat thin ice (<30 cm thick) is a common ice type in the Bohai Sea, China. Ice thickness detection is important to offshore exploration and marine transport in winter. Synthetic aperture radar (SAR) can be used to acquire sea ice data in all weather conditions, and it is a useful tool for monitoring sea ice conditions. In this paper, we combine a multi-layered sea ice electromagnetic (EM) scattering model with a sea ice thermodynamic model to assess the determination of the thickness of flat thin ice in the Bohai Sea using SAR at different frequencies, polarization, and incidence angles. Our modeling studies suggest that co-polarization backscattering coefficients and the co-polarized ratio can be used to retrieve the thickness of flat thin ice from C- and X-band SAR, while the co-polarized correlation coefficient can be used to retrieve flat thin ice thickness from L-, C-, and X-band SAR. Importantly, small or moderate incidence angles should be chosen to avoid the effect of speckle noise.  相似文献   

A new record of a flathead fish (Teleostei: Platycephalidae) from China based on morphological characters and DNA barcoding   总被引：2，自引：0，他引：2  

秦岩  宋娜  邹建伟  张朝晖  程光平  高天翔  张秀梅 《中国海洋湖沼学报》2013,31(3):617-624

A new record of Platycephalus sp.1 (sensu Nakabo, 2002) was documented based on morphological characters and DNA barcoding. We collected 174 specimens of the genus Platycephalus from Chinese coastal waters of Dongying, Qingdao, Zhoushan, and Beihai. Samples were identified as Platycephalus sp.1 morphologically. The coloration, meristic traits, and morphometric measurements are consistent with previously published records. In brief, it is an orange-brown flathead fish with dark brown spots scattered on head and body, lateral line scales 83 to 99 with one or two spine-bearing anteriormost pored scale, no yellow blotch on the caudal fin. Cytochrome oxidase I subunit (COI) gene fragments were sequenced for phylogenetic analysis. The mean evolutionary distance within the species Platycephalus sp.1 was 0.1%. Net evolutionary distances between Platycephalus sp.1 and other species of Platycephalus ranged from 10.8% to 19.7%, which is much greater than the threshold for species delimitation. The COI sequence analysis strongly supports the validity of Platyceohalus sp.1 at genetic level.  相似文献