Rare earth elements and Opal/CaCO<Subscript>3</Subscript> ratio of sinking particles observed with a time-series sediment trap at the mouth of Tokyo Bay     

Nobuyuki Takahashi  Shinichiro Noriki 《Journal of Oceanography》2007,63(6):941-951

A time-series sediment trap was deployed from December 1994 to February 2002 at the mouth of Tokyo Bay (35°03′ N, 139°40′ E; water depth, 850 m). Sinking particles were obtained with a time interval of one week at a depth of approximately 100 m above the sea floor. Observed total mass fluxes varied from 3.3 to 226.7 g/m²/day with an average of 28.0 g/m²/day. Concentrations of rare earth elements, Al, Ca and Si in particulate materials were measured. The combustible fraction at 450°C is assumed to be equivalent to the organic matter content. Contents of biogenic materials, namely organic matter, opal and calcium carbonate, were about 30% and the content of lithogenic material was about 70%. Using La/Yb ratios of particles from the sediment trap and Tama-gawa River and surface sediment of Tokyo Bay, it was estimated that about 50% of the lithogenic particles collected in the sediment trap at the mouth of Tokyo Bay originated from resuspended surface sediment in Tokyo Bay. An increasing trend of Opal/CaCO₃ ratio in the sinking particles was found in the spring season. It is suggested that the relative increase of diatoms is due to the decreasing dissolved inorganic nitrogen input into Tokyo Bay.  相似文献   

Gravitational Sedimentation Behavior of Sensitive Marine Ariake Clays     

Zhenshun Hong  Takehito Negami  Hailun Guo 《Marine Georesources & Geotechnology》2004,22(1):49-63

It has been well documented that natural marine Ariake clays are sensitive clays. In this study, extensive data of marine Ariake clays are obtained to investigate the gravitational compression behavior for sensitive clays. Analysis results indicate that the compression behavior of remolded Ariake clays is not different from that of other remolded/reconstituted soils. But natural Ariake clays do not follow the gravitational compression pattern reported by Skempton (1970) for natural sedimentary soils. At a given value of effective overburden pressure, the void ratios of natural Ariake clays are almost independent of liquid limits. Most natural Ariake clays lie above the sedimentation compression line proposed by Burland (1990). When the liquid limit is larger than 90% and the ratio of natural water content over liquid limit ranges 0.8-1.1, the natural Ariake clays lie around the sedimentation compression line. In addition, the natural Ariake clay with higher value of the ratio of natural water content over liquid limit lies above the natural Ariake clay with lower value of the ratio of natural water content over liquid limit. Salt removal is the most probable cause for such a phenomenon.  相似文献   

利用高密度电阻率法进行断层破碎带探查的数值模拟方法   总被引：2，自引：0，他引：2  

郭秀军  王兴泰 《中国海洋大学学报(自然科学版)》2001,31(5):755-761

为明确不同条件下断层破碎带的异常特征 ,提高高密度电阻率法 (HDR)的应用效果 ,该文在大量探测实例的基础上提出断层破碎带的地电模型 ;用有限元数值模拟的方式计算出不同地表电性层的情况下 ,高、低阻断层破碎带在不同电测的异常特征并确定最佳采集装置形式 ;并正演模拟倾斜断层的异常分布形态 ,给出为提高视电阻率断面对断层产状反映能力的数据处理方法  相似文献   

Maximum likelihood and non-parametric methods for estimating trawl footrope selectivity     

Munro  Peter T.; Somerton  David A. 《ICES Journal of Marine Science》2001,58(1):220-229

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Simulation of upper-ocean biogeochemistry with a flexible-composition phytoplankton model: C, N and Si cycling in the western Sargasso Sea     

Mathieu Mongin  David M. Nelson  Philippe Pondaven  Mark A. Brzezinski  Paul Trguer 《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(12):1445-1480

We report the first application of a biogeochemical model in which the major elemental composition of the phytoplankton is flexible, and responds to changing light and nutrient conditions. The model includes two phytoplankton groups: diatoms and non-siliceous picoplankton. Both fix C in accordance with photosynthesis-irradiance relationships used in other models and take up NO₃⁻ and NH₄⁺ (and Si(OH)₄ for diatoms) following Michaelis-Menten kinetics. The model allows for light dependence of photosynthesis and NO₃⁻ uptake, and for the observed near-total light independence of NH₄⁺ uptake and Si(OH)₄ uptake. It tracks the resulting C/N ratios of both phytoplankton groups and Si/N ratio of diatoms, and permits uptake of C, N and Si to proceed independently of one another when those ratios are close to those of nutrient-replete phytoplankton. When the C/N or Si/N ratio of either phytoplankton group indicates that its growth is limited by N, Si or light, uptake of non-limiting elements is controlled by the content of the limiting element in accordance with the cell-quota formulation of Droop (J. Mar. Biol. Ass. U.K 54 (1974) 825).We applied this model to the Bermuda Atlantic Time-series Study (BATS) site in the western Sargasso Sea. The model was tuned to produce vertical profiles and time courses of [NO₃⁻], [NH₄⁺] and [Si(OH)₄] that are consistent with the data, by adjusting the kinetic parameters for N and Si uptake and the rate of nitrification. The model then reproduces the observed time courses of chlorophyll-a, particulate organic carbon and nitrogen, biogenic silica, primary productivity, biogenic silica production and POC export with no further tuning. Simulated C/N and Si/N ratios of the phytoplankton indicate that N is the main growth-limiting nutrient throughout the thermally stratified period and that [Si(OH)₄], although always limiting to the rate of Si uptake by diatoms, seldom limits their growth rate. The model requires significant nitrification in the upper 200 m to yield realistic time courses and vertical profiles of [NH₄⁺] and [NO₃⁻], suggesting that NO₃⁻ is not supplied to the upper water column entirely by physical processes. A nitrification-corrected f-ratio (f_NC), calculated for the upper 200 m as: (NO₃⁻ uptake—nitrification)/(NO₃⁻ uptake+NH₄⁺ uptake) has annual values ranging from only 0.05–0.09, implying that 90–95% of the N taken up annually by phytoplankton is supplied by biological regeneration (including nitrification) in the upper 200 m. Reported discrepancies between estimates of organic C export based on seasonal chemical changes and POC export measured at the BATS site can be almost completely resolved if there is significant regeneration of NO₃⁻ via organic-matter decomposition in the upper 200 m.  相似文献   

氮、磷比对两种赤潮藻生长特性的影响及藻间竞争作用   总被引：13，自引：1，他引：13  

康燕玉  梁君荣  高亚辉  林荣澄  高华  邢小丽  马捷  骆巧琦 《海洋学报》2006,28(5):117-122

研究了两种赤潮藻即假微型海链藻(Thalassiosira pseudonana Hasleet Heimdalh)和裸甲藻(Gymnodinium sp.)在不同氮磷比培养条件下的生长特性和藻间竞争作用,探讨了氮磷含量及其比值对赤潮爆发的影响机理.结果表明,在N/P=16条件下,假微型海链藻的最大比增长率最高、相对生长常数最大、平均倍增时间最短,叶绿素a含量最高,说明该N/P值是假微型海链藻最佳生长营养盐条件.对裸甲藻而言,N/P=6是其最佳生长的营养盐条件.叶绿素a含量受N/P值的影响和藻细胞密度所受的影响趋势基本一致.不同N/P值对藻间竞争作用和群落演替的总体影响不明显,都呈现先硅藻后甲藻的群落演替规律.裸甲藻可能具有利用体内磷来维持生长的特点.  相似文献   

Effect of changes in reproductive potential on perceived productivity of three Northwest Atlantic cod (Gadus morhua) stocks     

Morgan  M. Joanne; Brattey  John 《ICES Journal of Marine Science》2005,62(1):65-74

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闽江口的盐、淡水混合   总被引：4，自引：1，他引：4       下载免费PDF全文

潘定安  沈焕庭 《海洋与湖沼》1993,24(6):599-608

采用盐、淡水混合比的概念研究闽江口的混合状态，并确定了分层、部分混合、高度混合３种类型的分类指标。研究表明，闽江口主要水道的盐、淡水混合以部分混合为主，其次是分层，高度混合出现的机率较少；盐水异重流发育良好，混合状态的变化与潮流速的变化不相一致；盐水入侵时混合比相对较小，后退时相对较大。闽江口是一个径、潮量比值较小的强潮河口，按照一般规律，其盐、淡水混合应该出现高度混合型，但在闽江口的主汊道中发生  相似文献   

磷酸盐、硝酸盐组成对海洋赤潮藻生长的影响   总被引：23，自引：2，他引：23  

王修林  邓宁宁  祝陈坚  韩秀荣  李克强  辛宇  陈莉莉 《中国海洋大学学报(自然科学版)》2004,34(3):453-460

应用 1次培养实验方法研究了不同组成磷酸盐 (PO4- P)和硝酸盐 (NO3 - N)对新月菱形藻、旋链角毛藻和中肋骨条藻 3种海洋赤潮藻生长的影响。结果表明 ,L ogistic生长模型可以很好地描述不同组成 PO4- P和 NO3 - N条件下 3种海洋赤潮藻生长状况 ,其中拟合相关系数 R2 =0 .95± 0 .0 3。进一步研究表明 ,3种海洋赤潮藻均存在营养盐生长阈值 C*PO4,C*NO3 ,在本文实验条件下新月菱形藻的 C*PO4为 1.72μmol· L-1,C*NO3 为 4 0 .4 2μmol· L-1;旋链角毛藻的分别为 2 .0 7μmol· L-1和 4 4.76 μmol· L-1;中肋骨条藻的分别为 1.13μmol· L-1和 30 .2 6 μmol· L-1。当 PO4- P,NO3 - N初始浓度分别小于其营养盐生长阈值 C*PO4,C*NO3 时 ,随其初始浓度增加会促进 3种赤潮藻生长 ,但当初始浓度大于营养盐生长阈值时 ,随营养盐初始浓度增加反而会逐渐限制其生长。这表明 3种海洋赤潮藻都存在 1个适宜其生长的 (N∶ P) 最佳值 ,其中新月菱形藻的 (N∶ P) 最佳值 =2 0∶ 1,旋链角毛藻的 (N∶ P) 最佳值 =19∶ 1,中肋骨条藻的 (N∶ P) 最佳值 =32∶ 1。  相似文献   

137°E断面北赤道流、黑潮变异和黑潮大弯曲的关系   总被引：1，自引：0，他引：1  

王元培 《海洋科学》1995,19(1):42-47

分析了１９７２～１９８８年１３７Ｅ断面资料,结果表明,北赤道流和黑潮、黑潮 和黑潮逆流、北赤道流和热带水以及黑潮、黑潮逆流和亚热带水等,都有０．０１以上 显著水平相关。黑潮既受制于西太平洋大尺度海洋环流,还受大暖涡变化的影响。 北赤道流递减率反应了亚热带环流西部的辐合状况,它的变化是导致日本以南大 暖涡迁移,黑潮路径变化、停滞的主要原因。  相似文献