Vertical characteristics revealed by biweekly and synoptic variability of upper sea temperature in the northern South China Sea

On the basis of the analysis of the sea temperature data that are observed from the three automatic temperature line acquisition sysem mooring buoys deployed in the central South China Sea (SCS) during South China Sea monsoon experiment, vertical features of biweekly and synoptic variability are discussed. There are five vertical modes, that is, subsurface temperature variability is in phase with,out of phase with, leads to, lags the surface temperature variability, and at depths within the subsurface layer the upper and lower temperature variations are out of phase. The formation of these vertical modes is related to the property of low-level atmospheric forcing and to the background in atmosphere and ocean. Wind stress curl is the main driving factor in forming Modes 1 and 3, and wind stresses in forming Modes 2 and 4.     

Last glacial terrestrial vegetation record of leaf wax n-alkanols in the northern South China Sea: Contrast to scenarios from long-chain n-alkanes

Long-chain n-alkanols and n-alkanes in core sediments from the northern South China Sea (SCS) were measured to make a comparison during terrestrial vegetation reconstruction from ~42 ka to ~7 ka. The results showed that terrestrial vegetation record from long-chain n-alkanes matched well with previous studies in nearby cores, showing that more C₄ plants developed during the Last Glacial Maximum (LGM) and C₃ plants dominated in the interglacial period. However, these scenarios were not revealed by terrestrial vegetation reconstruction using long-chain n-alkanols, which showed C₃ plant expansion during the LGM. The discrepancy during the interglacial period could be attributed to the aerobic degradation of functionalized long-chain n-alkanols in the oxygen-rich bottom water, resulting in poor preservation of terrestrial vegetation signals. On the other hand, the different advantages of functionalized n-alkanols and non-functional n-alkanes to record local and distal vegetation signals, respectively, may offer a potential explanation for the contradiction during the LGM when the SCS was characterized by low-oxygen deep water. Nevertheless, large variations on n-alkyl lipid compositions in C₃/C₄ plants could play a part in modulating sedimentary long-chain n-alkanols and n-alkanes toward different vegetation signals, thereby suggesting that caution must be taken in respect to the terrestrial vegetation reconstruction using long-chain n-alkanes and long-chain n-alkanols.     

南海北部海域表层沉积物底栖有孔虫分布特征及影响因素

有孔虫在海洋环境指示方面具有重要意义,对现代环境中有孔虫的分布及影响因素进行研究有助于利用有孔虫对地质历史时期的沉积环境进行还原。我国南海海域辽阔,南海有孔虫的相关研究很早便有报道。对我国南海北部海域表层沉积物中的底栖有孔虫分布特征进行了描述,研究区以玻璃质壳底栖有孔虫占主导,胶结壳其次,瓷质壳最少。根据底栖有孔虫的分布特征划分了4个底栖有孔虫组合,组合1为Heterolepa subpraecincta - Hanzawaia mantaensis - Rotalinoides gaimardii;组合2为Bulimina marginate - Lagena substriata;组合3为Elphidium advenum - Pararotalia nipponica;组合4 为Recurvoides contortus - Ammodisus cretaceous - Bulimina aculeata。对影响该区域底栖有孔虫分布的环境因素进行了探究,结果表明,温度、盐度、底质类型等对底栖有孔虫的分布均存在一定程度的影响,海流对研究区底栖有孔虫时空分布的影响值得进一步探究。     

Characteristics and origins of middle Miocene mounds and channels in the northern South China Sea

Numerous elongated mounds and channels were found at the top of the middle Miocene strata using 2D/3D seismic data in the Liwan Sag of Zhujiang River Mouth Basin(ZRMB) and the Beijiao Sag of Qiongdongnan Basin(QDNB). They occur at intervals and are rarely revealed by drilling wells in the deepwater areas. Origins of the mounds and channels are controversial and poorly understood. Based on an integrated analysis of the seismic attribute, palaeotectonics and palaeogeography, and drilling well enco...     

东海太平洋褶柔鱼角质颚的形态学分析

依据2010年9月及2011年5月、9月东海渔业资源底拖网调查采集的139尾(雌性66尾,雄性73尾)太平洋褶柔鱼(Todarodes pacificus)样本的胴长、体重和角质颚各部分的长度数据,分析了东海太平洋褶柔鱼角质颚的形态学特征。结果表明:(1)太平洋褶柔鱼角质颚上、下颚的喙长(RL)、头盖长(HL)、脊突长(CL)、翼长(WL)、翼宽(WW)等长度差异较大;(2)伴随RL的增长,HL、CL、WL、WW呈现极显著的异速生长特征(P<0.001);(3)各长度指标随胴长、体重的增长呈显著的线性增长趋势;(4)RL/CL、HL/CL的比值非常稳定,随胴长、体重的变化很小,可作为东海太平洋褶柔鱼角质颚形态特征的稳定指标。     

南海晚第四纪的硅藻遗体及其地质意义 Ⅴ.沟纹藻属

硅藻门（Bacillariophyta）沟纹藻属（LiriogrammaKolbe）在我国是1个新记录的属。该属最先由Kolbe（1954）在西太平洋赤道区（2°52＇S，89°50＇W，水深3225m）的柱状样沉积物中找到1种，订名L．petterssonii。之后，又在1955年从大西洋（0°7＇N，18°12＇E；0°8＇N，16°19＇E）和太平洋（6°44＇N，129°28＇W；2°52＇S，89°5＇W）的柱状样沉积物中找到另1种，订名L．hustedtii。笔者在南海第四纪的一个柱状样，距今约120ka（晚更新世）至11ka（全新世）的沉积物里找到了迄今该属已记录的2个种。此外，还记录了新组合的种：Liriogrammasarcophagu（Wallich）nov．comb．     

东海西湖凹陷平北地区表层沉积物特征及其成因初探

对研究区域的３７０个站位,１０８４个样品进行了粒度分析,对其中的部分样品进行了重矿物、古生物的分析和鉴定,发现东海西湖凹陷平片地区表层改造砂的特征与一般的规律有较大的差别,这种独特的表层沉积物特征的形成原因主要和所处的地貌部位有关。     

Annual and Seasonal Variations of the Sea Surface Heat Fluxes in the East Asian Marginal Seas

Based on the twice-daily marine atmospheric variables which were derived mostly from the weather maps for 18 years period from 1978 to 1995, the surface heat flux over the East Asian marginal seas was calculated at 0.5°×0.5° grid points twice a day. The annual mean distribution of the net heat flux shows that the maximum heat loss occurs in the central part of the Yellow Sea, along the Kuroshio axis and along the west coast of the northern Japanese islands. The area off Vladivostok turned out to be a heat-losing region, however, on the average, the amount of heat loss is minimum over the study area and the estuary of the Yangtze River also appears as a region of the minimum heat loss. The seasonal variations of heat flux show that the period of heat gain is longest in the Yellow Sea, and the maximum heat gain occurs in June. The maximum heat loss occurs in January over the study area, except the Yellow Sea where the heat loss is maximum in December. The annual mean value of the net heat flux in the East/Japan Sea is −108 W/m² which is about twice the value of Hirose et al. (1996) or about 30% higher than Kato and Asai (1983). For the Yellow Sea, it is about −89 W/m² and it becomes −75 W/m² in the East China Sea. This increase in values of the net heat flux comes mostly from the turbulent fluxes which are strongly dependent on the wind speed, which fluctuates largely during the winter season. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparative assessment of nitrogen fixation rate by 15N2 tracer assays in the South China Sea

Nitrogen fixation is one of the most important sources of new nitrogen in the ocean and thus profoundly affects the nitrogen and carbon biogeochemical processes. The distribution, controlling factors, and flux of N₂ fixation in the global ocean remain uncertain, partly because of the lack of methodological uniformity. The 15N₂ tracer assay (the original bubble method → the 15N₂-enriched seawater method → the modified bubble method) is the mainstream method for field measurements of N₂ fixation rates (NFRs), among which the original bubble method is the most frequently used. However, accumulating evidence has suggested an underestimation of NFRs when using this method. To improve the availability of previous data, we compared NFRs measured by three 15N₂ tracer assays in the South China Sea. Our results indicate that the relationship between NFRs measured by the original bubble method and the 15N₂-enriched seawater method varies obviously with area and season, which may be influenced by incubation time, diazotrophic composition, and environmental factors. In comparison, the relationship between NFRs measured by the original bubble method and the modified bubble method is more stable, indicating that the N₂ fixation rates based on the original bubble methods may be underestimated by approximately 50%. Based on this result, we revised the flux of N₂ fixation in the South China Sea to 40 mmol/(m2·a). Our results improve the availability and comparability of literature NFR data in the South China Sea. The comparison of the 15N₂ tracer assay for NFRs measurements on a larger scale is urgently necessary over the global ocean for a more robust understanding of the role of N₂ fixation in the marine nitrogen cycle.