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101.
Sinking particulate matter were obtained from twelve depths using free-drifting sediment trap arrays which were deployed in the upper 2,000 m water column of the Izu Trench, northwest Pacific Ocean. The largest flux of 146 mgC m–2 day–1 was observed at 150 m depth. The flux generally decreased with depth below the maximum, however, minor flux peaks occurred at 1,000 and 1,250 m depth (>30 mgC m–2 day–1). Sinking large particles (>100 µm) were composed of fecal pellets typical of crustaceans, macroscopic aggregates, and planktonic organisms and their fragments. Three major components constituted 19%, 20% and 29%, respectively, of the total carbon flux (averaged from the fluxes at five depths; 50, 100, 150, 1,000 and 2,000 m). Among them, fecal pellet flux and large organism flux were well correlated with the total flux. The close correspondence between the fecal flux and the total carbon flux suggests that the latter is derived from a group of variables including other biogenic matter, among which fecal pellet is one of the leading factors controlling total flux, though the latter is only a minor covariable in quantity. Vertical flux profiles of fecal pellets and their internal constituents revealed some new inputs of feces occurring through the water column. This phenomenon implies that downward transportation of organic material is characterized by feeding and egestion activities of zooplankton, including overlapping processes of sinking and dispersion of large fecal particles and repackaging of dispersed small particles. 相似文献
102.
Importance of feeding on regenerable parts of prey for juvenile stone flounder Platichthys bicoloratus in estuarine habitats 总被引:3,自引:0,他引:3
Takeshi Tomiyama Satoshi Katayama Michio Omori Hitoshi Honda 《Journal of Sea Research》2005,53(4):297-308
Prey availability is one of the most important factors affecting the quality of nursery grounds. Estuaries play an important role as nursery grounds for juvenile stone flounder, but the mechanism behind the consistently high availability of prey has never been examined. This study investigates which prey is mainly selected by juvenile stone flounder (15–55 mm standard length) in the estuary of the Natori River, northern Japan. In a cage experiment, juveniles showed positive selection for the palps of the spionid polychaete Pseudopolydora kempi in March, and for the siphons of the bivalve Nuttallia olivacea in April, May and June in both sandy and muddy-sand habitats. This selective predation showed that sublethal predation on regenerable parts of invertebrates is important for stone flounder. Nuttallia olivacea, the dominant bivalve in the estuary, was more abundant and in better somatic condition in the sandy area in spite of the stronger siphon-cropping pressure by juvenile stone flounder. These results confirm that sublethal predation on highly abundant benthos plays an important role in forming estuarine habitats into areas of high prey availability for juvenile stone flounder, which leads to their high growth rate. 相似文献
103.
Ayako Shinozaki Hiroyuki Kagi Hisako Hirai Hiroaki Ohfuji Taku Okada Satoshi Nakano Takehiko Yagi 《Physics and Chemistry of Minerals》2016,43(4):277-285
Stability and phase relations of coexisting enstatite and H2 fluid were investigated in the pressure and temperature regions of 3.1–13.9 GPa and 1500–2000 K using laser-heated diamond-anvil cells. XRD measurements showed decomposition of enstatite upon heating to form forsterite, periclase, and coesite/stishovite. In the recovered samples, SiO2 grains were found at the margin of the heating hot spot, suggesting that the SiO2 component dissolved in the H2 fluid during heating, then precipitated when its solubility decreased with decreasing temperature. Raman and infrared spectra of the coexisting fluid phase revealed that SiH4 and H2O molecules formed through the reaction between dissolved SiO2 and H2. In contrast, forsterite and periclase crystals were found within the hot spot, which were assumed to have replaced the initial orthoenstatite crystals without dissolution. Preferential dissolution of SiO2 components of enstatite in H2 fluid, as well as that observed in the forsterite H2 system and the quartz H2 system, implies that H2-rich fluid enhances Mg/Si fractionation between the fluid and solid phases of mantle minerals. 相似文献
104.
Hydration of rhyolitic glass during weathering as characterized by IR microspectroscopy 总被引:1,自引:0,他引:1
Tadashi Yokoyama Satoshi Okumura Satoru Nakashima 《Geochimica et cosmochimica acta》2008,72(1):117-125
The mechanism and rate of hydration of rhyolitic glass during weathering were studied. Doubly polished thin sections of two rhyolites with different duration of weathering (Ohsawa lava: 26,000 yr, Awanomikoto lava: 52,000 yr) were prepared. Optical microscope observation showed that altered layers had developed along the glass surfaces. IR spectral line profile analysis was conducted on the glass sections from the surface to the interior for a length of 250 μm and the contents of molecular H2O (H2Om), OH species (OH) and total water (H2Ot) were determined. The diffusion profile of H2Om in Ohsawa lava extends beyond the layer observed by optical microscope. The content of H2Om in the hydrated region is much higher than that of OH species. Thus, the reaction from H2Om to OH appears to be little and H2Om is the dominant water species moving into the glass during weathering. Based on the concentration profiles, the diffusion coefficients of H2Om(DH2Om) and H2Ot(DH2Ot) were determined to be 2.8 × 10−10 and 3.4 × 10−10 μm2 s−1 for Ohsawa lava, and 5.2 × 10−11 and 4.1 × 10−11 μm2 s−1 for Awanomikoto lava, respectively. The obtained DH2Om during weathering are more than 2-3 orders of magnitude larger than the diffusion coefficient at ∼20 °C that is extrapolated from the diffusivity data for >400 °C. This might suggest that the mechanism of water transport is different at weathering conditions and >400 °C. 相似文献
105.
James B. S. G. Greensky Wojciech Walter Czech David A. Yuen Michael Richard Knox Megan Rose Damon Shi Steve Chen M. Charley Kameyama 《Visual Geosciences》2008,13(1):105-115
We have developed a new strategy and espouse a novel paradigm for large-scale computing and real-time interactive visualization.
This philosophy calls for intense interactive sessions for a couple of hours at a time at the expense of storing data on many
disk drives during regular or heroic runs on massively parallel systems. We have already carried out successfully real-time
volume-rendering visualization by employing hundreds of processors for a grid with over 25 million unknowns. Both Cartesian
and spherical 3D mantle convection are visualized. The volume-rendered images are viewed on a large display device, with many
panels holding around 13 million pixels. We will employ a software strategy involving an hierarchical rendering service, which
will have as software an Ajax interface for interactive visualization of large data sets on many different platforms from
desktop PC’s to hand-held devices, such as the OQO and the Nokia N-800. An option for stereo viewing is also implemented.
We have installed a user interface as web application, using Java and Ajax framework in order to achieve over the Internet
reasonable accessibility to our ongoing runs. Our goal is to expand the array of interactive devices, which will make it feasible
to carry out ubiquitous visualization and monitoring of large-scale simulations or onsite events and to allow for collaborations
across oceans. 相似文献
106.
应用Terra/MODIS卫星数据估算洞庭湖蓄水量的变化 总被引:14,自引:0,他引:14
以洞庭湖为例,利用2002年的美国Terra/MODIS卫星数据,以16天为周期将全年划分为23个时段,分别对湖区水位和蓄水量分布特征和变化规律进行动态监测和综合分析。具体测算方法包括以下4个步骤: (1) 根据湖区特性,将整个洞庭湖分为3个部分:自西向东依此是西洞庭湖 (WDL), 南洞庭湖 (SDL) 和东洞庭湖 (EDL)。这3个部分的蓄水量之和就是整个洞庭湖的总蓄水量。(2) 以水体和陆地的光谱差异为基础,使用Terra/MODIS卫星的NDVI 数据识别并量测湖区水面积。(3) 将湖区水面影像同湖区数字高程模型DEM相叠加,以被监测的湖区水面的平均高度值作为水面高度。水面高度与湖底高度的差即为相应点的水深。(4) 按50 m×50 m网格大小和相应位置的水深的乘积来计算每个水柱体积。最后,将整个湖内的所有水柱的体积值累加便得到洞庭湖的总蓄水量。用上述方法测算的水位和蓄水量与实测资料进行了比较表明,两者具有很好的一致性。 相似文献
107.
Tetsuya Nishikawa Yutaka Hori Satoshi Nagai Kazutaka Miyahara Yukinobu Nakamura Kazuhiro Harada Minoru Tanda Takehiko Manabe Kuninao Tada 《Estuaries and Coasts》2010,33(2):417-427
Long-term monitoring of water quality and phytoplankton was conducted at 19 sampling stations in Harima-Nada, eastern Seto Inland Sea, Japan for 35 years from 1973 to 2007. There were two significant long-term changes, an increase in winter water temperatures of 0.042°C year?1, and a decrease in dissolved inorganic nitrogen (DIN) from about 10 μM in the 1970s to ~5 μM in the late 1990s due to the reduction in nutrient inputs. DIN concentrations and total phytoplankton cell density were both higher during the 1970s to the early 1980s and then exhibited a significant decrease in the mid 1980s and remained relatively constant thereafter. Diatoms were the dominant phytoplankton group (>90%) over the 35-year period, and there was a dramatic shift from Skeletonema dominance (~70%) to Chaetoceros in the mid 1980s. This shift in diatom species may be attributed to differences in the life cycle of Skeletonema and Chaetoceros and the response to the decrease in DIN concentration. 相似文献
108.
Ayumi Asai Takaaki Yokoyama Masumi Shimojo Satoshi Masuda Kazunari Shibata 《Journal of Astrophysics and Astronomy》2006,27(2-3):167-173
We report a detailed examination about the relationship between the evolution of the Hα flare ribbons and the released magnetic
energy during the April 10 2001 flare. In the Hα images, several bright kernels are observed in the flare ribbons. We identified
the conjugated foot-points, by analyzing the lightcurves at each Hα kernels, and showed their connectivities during the flare.
Then, based on the magnetic reconnection model, we calculated quantitatively the released energy by using the photospheric
magnetic field strengths and separation speeds of the Hα flare ribbons. Finally, we examined the downward motions which are
observed at the Hα kernels. We found that the stronger the red-asymmetry tends to be associated with the brighter the Hα kernel. 相似文献
109.
Satoshi Hinata 《Solar physics》1987,109(2):321-333
As the electrical conductivity along the magnetic field in solar atmosphere is large, parallel electric fields have been neglected in most investigations. We will first demonstrate their importance for post-flare loops, and then introduce a model for them which takes into account the effect of parallel electric fields. The electric field calculated from the model is consistent with the electric field observed by Foukal et al. (1983). 相似文献
110.
Terrigenous loading into enclosed water bodies has been blamed for eutrophic conditions marked by massive algal growth and subsequent hypoxia due to decomposition of dead algal cells. This study aims to describe the eutrophication and hypoxia processes in a semi-enclosed water body lying near a big metropolis. Phosphorus mass balance in a small inlet, Ohko Inlet, located at the head of Hiroshima Bay, Japan, was quantified using a numerical model. Dissolved inorganic phosphorous inflow from Kaita Bay next to the inlet was five times higher than that from terrigenous load, which may cause an enhancement of primary production. Therefore, it was concluded that not only the reduction of material load from the land and the suppression of benthic flux are needed, but also reducing the inflow of high phosphorus and oxygen depleted water from Kaita Bay will form a collective alternative measure to remediate the environmental condition of the inlet. 相似文献