Minor and trace element incorporation into branching coral Acropora nobilis skeleton     

Kotaro Shirai  Tatsunori Kawashima  Tsuyoshi Watanabe  Naoto Takahata  Yuji Sano 《Geochimica et cosmochimica acta》2008,72(22):5386-5400

Chemical and isotopic compositions of the Acropora nobilis skeleton were analyzed at various spatial resolutions to investigate the mechanism by which elements are incorporated into the skeleton. Chemical and isotopic profiles along growth axes of axial and radial corallites did not show seasonal variation, with the exception of the δ¹⁸O profile of the axial corallite. Detailed observations of the skeletal structure revealed that the skeletal density increased with distance from the tip because secondarily precipitated aragonite (here called the “infilling” skeleton) filled pore spaces in the “framework” skeleton. Microscale element analyses revealed that main part of the infilling skeleton had lower Mg/Ca and higher Sr/Ca and U/Ca than the framework skeleton. At microscale, Sr/Ca and U/Ca were positively correlated with each other, and negatively correlated with Mg/Ca but only weakly. The results showed that the infilling skeleton differed significantly from the adjacent framework skeleton in terms of not only formation chronology but also chemical composition, and that the bulk composition was influenced by the infilling/framework skeletal ratio. In order to use the Acropora skeleton as a paleoclimate archive, the relationship between environmental factors and the chemical composition of each skeletal component needs to be established.  相似文献   

Ostwald ripening of garnet in high P/T metamorphic rocks     

Kazuhiro Miyazaki 《Contributions to Mineralogy and Petrology》1991,108(1-2):118-128

This paper presents a theoretical formulation of Ostwald ripening of garnet and discusses the importance of the process during high pressure and low temperature (high P/T) metamorphism. The growth rate of garnet due to Ostwald ripening is formulated for the system consisting of minerals and an intergranular medium. Crystal size distribution (CSD) of garnets are examined and compared with the theoretical distribution for Ostwald ripening. Two types of CSDs are recognized. One is consistent with the theoretical prediction of size distribution while the other is wider than the theoretical distribution. The former CSD applies to samples in which garnets show homogeneous spatial distributions. The latter CSD applies to samples in which garnets show heterogeneous spatial distributions such as in clusters or layers. These relations suggest that the heterogeneity of spatial distributions results in a heterogeneity of concentration of garnet, causing the wide distributions. The mean diameter (dg) has a large variation in samples having narrow distributions. Ostwald ripening explains well the similar patterns of CSD in these samples with different dg because of a scaling law. Compositional profiles of garnets with different size are consistent with Ostwald ripening rather than nucleation and growth kinetics. This suggests that the CSDs result from Ostwald ripening. Magnitude of heating rate will determine which mechanism controls CSD. Nucleation and growth kinetics are dominant when heating rate is large. On the other hand, Ostwald ripening is dominant when heating rate is small. CSDs of garnets in high P/T metamorphic rocks are consistent with the latter case.  相似文献   

Numerical study for specifying the major origin of low salinity water associated with <Emphasis Type="Italic">Chattonella</Emphasis> (Raphidophyceae) blooms in Tachibana Bay,Japan     

Kazuhiro?AokiEmail author  Manabu?Shimizu  Hiroshi?Kuroda  Toshifumi?Yamatogi  Naoya?Ishida  Shigeru?Kitahara  Keiji?Hirano 《Journal of Oceanography》2016,72(5):811-816

In both 2009 and 2010, massive Chattonella blooms occurred in Tachibana Bay. Observation results show that high cell densities of Chattonella were distributed in the central area of Tachibana Bay with low salinity water. Model results indicate that the low salinity water originated from the Ariake Sea and intruded into Tachibana Bay during the northerly or weak winds. It is suggested that low salinity water was mainly discharged from the northern area of the Ariake Sea. Northerly wind enhanced the horizontal advection of the low salinity water intruding into Tachibana Bay originating from the northern area of the Ariake Sea.  相似文献   

Application of finite volume coastal ocean model to hindcasting the wind-induced sea-level variation in Fukuoka bay     

Kazuhiro Aoki  Atsuhiko Isobe 《Journal of Oceanography》2007,63(2):333-339

The wind-induced sea-level variations at Hakata tidal station in winter are reproduced realistically using a one-way nested model. This nested model is constructed with a structured finite-difference Princeton Ocean Model (POM) for the Tsushima-Korea Straits, and an unstructured Finite Volume Coastal Ocean Model (FVCOM) for Fukuoka Bay divided into triangular-cell grids. The correlation coefficient and root-mean-square error between observed and modeled results are 0.742 and 1.88 [cm], respectively. Moreover, the results show that the nested model with FVCOM is more accurate than the model in which FVCOM is replaced with a high-resolution POM for Fukuoka Bay. This indicates that the nested model constructed with structured and unstructured models works effectively in hindcasting the wind-induced sea-level variations.  相似文献   

Growth inhibition of a red tide flagellate,Chattonella antiqua by copper     

Nakamura  Yasuo  Sawai  Kazuhiro  Watanabe  Masataka 《Journal of Oceanography》1986,42(6):481-486

Journal of Oceanography - Copper toxicity inChattonella antiqua (Raphidophyceae) was examined using an artificial seawater medium. The growth rate (Μ) was found to be a unique function of...  相似文献   

Effects of fixation and storage on flow cytometric analysis of marine bacteria     

Eriko Kamiya  Shinji Izumiyama  Masahiko Nishimura  James G. Mitchell  Kazuhiro Kogure 《Journal of Oceanography》2007,63(1):101-112

Flow cytometry (FCM) is now becoming a routine tool for the enumeration and optical characterization of bacteria in marine environments. We investigated the effects of sample fixation and storage upon flow cytometric determination of marine bacteria. Fixed and unfixed seawater samples were analyzed by FCM immediately aboard ship and/or later in the laboratory, and the appearances of the fluorescence signals and bacterial counts of these samples were compared. Fixation and storage led to the formation of multiple peaks in fluorescence histograms; this was also seen in 22 out of 36 samples frozen in liquid nitrogen. Fixation did not, but storage did induce a decrease of bacterial counts: a rapid decrease during the first 3 days followed by a slower decline. The decline of cell numbers in stored samples was expressed by a regression model. Our studies indicate that precaution is necessary when interpreting the data from fixed and/or stored marine bacterial samples analyzed by FCM. The possibility that the procedure of fixation and storage leads to the appearance of high DNA and low DNA bacterial groups should be considered.  相似文献   

Properties of sea ice and overlying snow in the Southern Sea of Okhotsk     

Takenobu Toyota  Shinya Takatsuji  Kazutaka Tateyama  Kazuhiro Naoki  Kay I. Ohshima 《Journal of Oceanography》2007,63(3):393-411

The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of 2003 to 2005 with the P/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length) was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer thickness of 12 cm, indicating that dynamic processes are essential to ice growth. The mean thickness of ice blocks and visual observations suggest that ridging dominates the deformation process above thicknesses of 30 to 40 cm. As for snow, it was found that faceted crystals and depth hoar are dominant (78%), as which is also common in the Antarctic sea ice, and is indicative of the strong vertical temperature gradients within the snow. Stable isotope measurements (δ¹⁸O) indicate that snow ice occupies 9% of total core length and that the mass fraction of meteoric ice accounts for 1 to 2% of total ice volume, which is lower than the Antarctic sea ice. Associated with this, the effective fractionation coefficient during the freezing of seawater was also derived. Snow ice was characterized by lower density, higher salinity, and nearly twice the gas content of ice of seawater origin. In addition, it is shown that the surface brine volume fraction and freeboard are well correlated with ice thickness, indicating some promise for remote sensing approaches to the estimation of ice thickness.  相似文献   

Trace metals in Japanese eel Anguilla japonica in relation to ecological migratory types and growth stages     

Dung Quang Le  Naoko Chino  Kotaro Shirai  Takaomi Arai 《Estuarine, Coastal and Shelf Science》2010

In order to understand the metal concentrations in Japanese eel Anguilla japonica, nine elements were analyzed in the livers of different migratory types of eels collected from Tokushima region (south Japan). Migratory types were defined by examining the Sr:Ca ratio in otoliths. The results showed that there were significant differences in V, Cr, Cd, and Pb concentrations among the migratory types. Mature-sea-eels show a higher risk of metal accumulation than other migratory types of eels, and the concentrations of Mn, Cu, and Zn in mature eels were significantly higher than those in immature eels. The study suggests that the eel liver is a valuable bioindicator for trace metals; however, when using the eel as a bioindicator to reveal the pollutants in aquatic systems, life history analysis should be carried out for accurate interpretation of the results.  相似文献   

Chemical and mineralogical compositions of two grains recovered from asteroid Itokawa          下载免费PDF全文

M. Ebihara  N. Shirai  S. Sekimoto  T. Nakamura  A. Tsuchiyama  J. Matsuno  T. Matsumoto  M. Tanaka  M. Abe  A. Fujimura  Y. Ishibashi  Y. Karouji  T. Mukai  T. Okada  M. Uesugi  T. Yada 《Meteoritics & planetary science》2015,50(2):243-254

Two silicate grains (RB‐QD04‐0049 and RA‐QD02‐0064, whose estimated masses are 0.050 μg and 0.048 μg, respectively) recovered from the asteroid Itokawa by the Hayabusa spacecraft were studied for their mineralogical characteristics by synchrotron X‐ray diffraction and synchrotron X‐ray microtomography and further analyzed for their bulk chemical compositions by instrumental neutron activation analysis (INAA). According to X‐ray tomography, RB‐QD004‐0049 is composed of olivine, high‐Ca pyroxene, plagioclase, Ca‐phosphate, and troilite, whereas RA‐QD002‐0064 entirely consists of olivine. INAA data are consistent with these mineral compositions except for rare earth elements (REEs). Although the grain RB‐QD004‐0049 contains measurable REEs, which seems to be consistent with the presence of Ca‐phosphate, their abundances are anomalously high. Very low abundance of Co implies less than 0.1 mass% of metals in these two grains by calculation, which is in contrast to the result for the previously analyzed grain RA‐QD02‐0049 (Ebihara et al., 2011). FeO/Sc ratios of the grains fall within the range of those for ordinary chondrite olivines, implying that these grains are extraterrestrial in origin. FeO/MnO ratios also confirm this conclusion and further suggest that the Hayabusa grains analyzed in this study are similar to material found in LL chondrites rather than CK chondrites although olivines from LL and CK chondrites have similar Fa# (molar% of Fe relative to [Fe+Mg] in olivine) (~30) to those of the Hayabusa grains including the two grains analyzed in this study.  相似文献   

Discovery of a large-scale clumpy structure around the Lynx supercluster at z∼ 1.27     

Fumiaki Nakata  Tadayuki Kodama  Kazuhiro Shimasaku  Mamoru Doi  Hisanori Furusawa  Masaru Hamabe  Masahiko Kimura  Yutaka Komiyama  Satoshi Miyazaki  Sadanori Okamura  Masami Ouchi †  Maki Sekiguchi  Yoshihiro Ueda  Masafumi Yagi  Naoki Yasuda 《Monthly notices of the Royal Astronomical Society》2005,357(4):1357-1362

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