An Ecosystem Model Including Nitrogen Isotopes: Perspectives on a Study of the Marine Nitrogen Cycle     

Chisato?YoshikawaEmail author  Yasuhiro?Yamanaka  Takeshi?Nakatsuka 《Journal of Oceanography》2005,61(5):921-942

We have developed an ecosystem model including two nitrogen isotopes (¹⁴N and ¹⁵N), and validated this model using an actual data set. A study of nitrogen isotopic ratios (δ¹⁵N) using a marine ecosystem model is thought to be most helpful in quantitatively understanding the marine nitrogen cycle. Moreover, the model study may indicate a new potential of δ¹⁵N as a tracer. This model has six compartments: phytoplankton, zooplankton, particulate organic nitrogen, dissolved organic nitrogen, nitrate and ammonium in a two-box model, and has biological processes with/without isotopic fractionation. We have applied this model to the Sea of Okhotsk and successfully reproduced the δ¹⁵N of nitrate measured in seawater and the seasonal variations in δ¹⁵N of sinking particles obtained from sediment trap experiments. Simulated δ¹⁵N of phytoplankton are determined by δ ¹⁵N of nitrate and ammonium, and the nitrogen f-ratio, defined as the ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation. Detailed considerations of biological processes in the spring and autumn blooms have demonstrated that there is a significant difference between simulated δ¹⁵N values of phytoplankton, which assimilates only nitrate, and only ammonium, respectively. We suggest that observations of δ ¹⁵N values of phytoplankton, nitrate and ammonium in the spring and autumn blooms may indicate the ratios of nutrient selectivity by phytoplankton. In winter, most of the simulated biogeochemical fluxes decrease rapidly, but nitrification flux decreases much more slowly than the other biogeochemical fluxes. Therefore, simulated δ¹⁵N values and concentrations of ammonium reflect almost only nitrification. We suggest that the nitrification rate can be parameterized with observations of δ¹⁵N of ammonium in winter and a sensitive study varying the parameter of nitrification rate.  相似文献   

Effect of seasonal change in gas transfer coefficient on air–sea CO2 flux in the western North Pacific     

Xuanrui Xiong  Yoshio Masuda  Taketo Hashioka  Tsuneo Ono  Yasuhiro Yamanaka 《Journal of Oceanography》2015,71(6):685-701

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Relationships between trace element concentrations and the stable nitrogen isotope ratio in biota from Suruga Bay,Japan     

Masahiro Sakata  Ai Miwa  Satoshi Mitsunobu  Yasuhiro Senga 《Journal of Oceanography》2015,71(1):141-149

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The H i content of star-forming galaxies at z= 0.24     

Philip Lah  Jayaram N. Chengalur  Frank H. Briggs  Matthew Colless  Roberto De Propris  Michael B. Pracy  W. J. G. de Blok  Shinobu S. Fujita  Masaru Ajiki  Yasuhiro Shioya  Tohru Nagao  Takashi Murayama  Yoshiaki Taniguchi  Masafumi Yagi  Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2007,376(3):1357-1366

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The GMRT EoR experiment: limits on polarized sky brightness at 150 MHz     

Ue-Li Pen  Tzu-Ching Chang  Christopher M. Hirata  Jeffrey B. Peterson  Jayanta Roy  Yashwant Gupta  Julia Odegova  Kris Sigurdson 《Monthly notices of the Royal Astronomical Society》2009,399(1):181-194

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Tidal alignments as a contaminant of redshift space distortions     

Christopher M. Hirata 《Monthly notices of the Royal Astronomical Society》2009,399(2):1074-1087

We investigate the effect of orientation-dependent selection effects on galaxy clustering in redshift space. It is found that if galaxies are aligned by large-scale tidal fields, then these selection effects give rise to a dependence of the observed galaxy density on the local tidal field, in addition to the well-known dependences on the matter density and radial velocity gradient. This alters the galaxy power spectrum in a way that is different for Fourier modes parallel to and perpendicular to the line of sight. These tidal galaxy alignments can thus mimic redshift space distortions (RSD), and thus result in a bias in the measurement of the velocity power spectrum. If galaxy orientations are affected only by the local tidal field, then the tidal alignment effect has exactly the same scale and angular dependence as the RSDs in the linear regime, so it cannot be projected out or removed by masking small scales in the analysis. We consider several toy models of tidal alignments and orientation-dependent selection, normalize their free parameter (an amplitude) to recent observations, and find that they could bias the velocity amplitude   f ( z ) G ( z )  by 5–10 per cent in some models, although most models give much smaller contamination. We conclude that tidal alignments may be a significant systematic error in RSD measurements that aim to test general relativity via the growth of large-scale structure. We briefly discuss possible mitigation strategies.  相似文献   

Impact of stem water storage on diurnal estimates of whole‐tree transpiration and canopy conductance from sap flow measurements in Japanese cedar and Japanese cypress trees     

Tomo'omi Kumagai  Sayaka Aoki  Kyoichi Otsuki  Yasuhiro Utsumi 《水文研究》2009,23(16):2335-2344

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Cooling and inferred exhumation history of the Ryoke metamorphic belt in the Yanai district, south-west Japan: Constraints from Rb–Sr and fission-track ages of gneissose granitoid and numerical modeling     

Takamoto Okudaira  Yasutaka Hayasaka  Osamu Himeno  Koichiro Watanabe  Yasuhiro Sakurai  Yukiko Ohtomo 《Island Arc》2001,10(2):98-115

Abstract The Ryoke metamorphic belt in south-west Japan consists mainly of I-type granitoids and associated low-pressure/high-temperature metamorphic rocks. In the Yanai district, it has been divided into three structural units: northern, central and southern units. In this study, we measured the Rb–Sr whole-rock–mineral isochron ages and fission-track ages of the gneissose granodiorite in the central structural unit. Four Rb–Sr ages fall in a range of ca 89–87 Ma. The fission-track ages of zircon and apatite are 68.9 ± 2.6 Ma and 57.4 ± 2.5 Ma (1σ error), respectively. Combining the newly obtained ages with previously reported (Th–)U–Pb ages from the same unit, thermochronologic study revealed two distinctive cooling stages; 1) a rapid cooling (> 40°C/Myr) for a period (~7 Myr) soon after the peak metamorphism (~ 95 Ma) and 2) the subsequent slow cooling stage (~ 5°C/Myr) after ca 88 Ma. The first rapid cooling stage corresponds to thermal relaxation of the intruded granodiorite magma and its associated metamorphic rocks, and to the uplift by a displacement along low-angle faults which initiated soon after the intrusion of the magma. Uplift by the later stage deformation having formed large-scale upright folds resulted in progress of the exhumation during the first stage. The average exhumation velocity of the stage is ≥ 2 mm/yr. During the second stage, the rocks were not accompanied by ductile deformation and were exhumed with the rate of 0.1–0.2 mm/yr. The difference in the exhumation velocity between the first and second cooling stages resulted from the difference in the thickness of the crust and in the activity of ductile deformation between the early and later stages of the orogenesis.  相似文献   

Characterization of sulfate ion in travertine     

Bokuichiro Takano  Yasuhiro Asano  Kunihiko Watanuki 《Contributions to Mineralogy and Petrology》1980,72(2):197-203

The mode of incorporation of sulfate ion in travertine was discussed on the basis of chemical compositions, i.r. and laser Raman spectra. These data strongly suggest that most of the sulfate ions in the calcitic travertine replace carbonate ions. This conclusion is in good harmony with the facts that calcite incorporates more sulfate ions than aragonite does and that the sulfate content of manganoan calcite decreases with increasing manganese content (Takano et al. 1977). Based on this conclusion, retarding effect of sulfate ion on the precipitation of calcite from solution was discussed.  相似文献   

BSRs and Associated Reflections as an Indicator of Gas Hydrate and Free Gas Accumulation: An Example of Accretionary Prism and Forearc Basin System along the Nankai Trough, off Central Japan   总被引：1，自引：0，他引：1  

Kei Baba  Yasuhiro Yamada 《Resource Geology》2004,54(1):11-24

Abstract. Multi-channel seismic data obtained from the Nankai accretionary prism and forearc basin system has been studied to elucidate the migration and accumulation process of gas to the BGHS and examine the distribution pattern of BSRs and characteristic reflections associated with them.
BSRs are distributed widely in the Nankai accretionary prism and associated forearc basins (33,000 km²) and 90 % of them have migration and recycling origins. The widest distribution of the BSRs can be seen at the prism. A correlation between the BSR distributions and prism size shows that the BSRs tend to be more well-developed in a prism of large size. This suggests that a large prism may produce much amount of gas-bearing fluids that migrate to the BGHS and form the BSRs (tectonic control), hi the forearc basins, the BSRs are identified at topographic highs, anticlines and basin margins (structural control).
The upward migration of gas-bearing fluids is carried out through permeable sand layers and as a result, the distribution of BSRs is confined to alternating beds of sand and mud facies (sedimentary control). However, if there is enough time for upward migration and accumulation of gas to the BGHS, the BSRs can be generated widely in low-permeable mud facies (time control).
Those results imply that structural, tectonic, sedimentary and time controls are primary factors to decide the distribution of BSRs in the Nankai Trough area.  相似文献