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31.
32.
Masahiro Sakata Masaki Yamada Satoshi Mitsunobu Yasuhiro Senga 《Journal of Oceanography》2012,68(5):807-813
The contribution of abiogenic and biogenic particles to trace-metal (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Ti, V, and Zn) composition was investigated for phytoplankton (primarily diatoms) collected in Shimizu Port, a coastal seawater region. Except for Cd, the trace metals occurred predominantly in lithogenic or nonlithogenic abiogenic particles associated with plankton. In contrast, it is likely that Cd in seawater is taken up intracellularly, and not adsorbed extracellularly by phytoplankton. The lower P-normalized quotas of Cd in Shimizu Port than in offshore regions may be because plankton are dominated by diatoms. 相似文献
33.
Shotaro Suzuki Ryo Kaneko Taketoshi Kodama Fuminori Hashihama Shuhei Suwa Iwao Tanita Ken Furuya Koji Hamasaki 《Journal of Oceanography》2017,73(3):383-395
The subtropical and tropical regions of the Pacific Ocean are less productive than other oceanic regions. Although particle association should be an important strategy for heterotrophic prokaryotes to survive in such environments, we have little information on particle-associated (PA) prokaryotes in these regions. The specific aim of this study was to determine bacterial and archaeal community structures in the PA assemblage in comparison to the free-living (FL) assemblage in the North Pacific Subtropical Gyre, the South Pacific Subtropical Gyre, and an eastern equatorial region of the Pacific Ocean. Community profiles and phylogenetic identities were obtained by denaturing gradient gel electrophoresis, 454-pyrosequencing, and cloning followed by Sanger sequencing of 16Sr RNA gene amplicons. The distribution patterns of some abundant groups in three regions and two lifestyles (PA and FL) are shown in this study. Also, the PA community structures of bacteria differed from the FL ones and exhibited higher diversity than the FL ones, while the archaeal community structures did not show significant differences between PA and FL assemblages. We found that specific phylotypes of Gammaproteobacteria and Flavobacteria were abundant in PA bacterial assemblages, suggesting that they prefer to attach and consume particulate organic matter. In summary, the surface seawater PA assemblages represent very different bacterial and archaeal community structures between three different oceanic regions, each of which had distinct PA and FL community structures. These results imply that environmental factors determine microbial community structures. 相似文献
34.
Fuminori Hashihama Shinko Kinouchi Shuhei Suwa Masahiro Suzumura Jota Kanda 《Journal of Oceanography》2013,69(3):357-367
Trace concentrations of labile dissolved organic phosphorus (LDOP) in oligotrophic seawater were measured by use of an enzymatic procedure and a nanomolar phosphate analytical system consisting of a gas-segmented continuous flow analyzer with a liquid waveguide capillary cell. LDOP, defined as DOP hydrolyzed by alkaline phosphatase (AP) from Escherichia coli, was quantified as the difference between the phosphate concentrations of the seawater sample with and without AP treatment. For sensitive measurement of LDOP, we found that phosphate contamination derived from commercially available AP must be corrected, and azide treatment before AP treatment proved effective in removing biological effect that occurs during DOP hydrolysis. Field observations at six stations of the western North Pacific and the East China Sea during the boreal summer revealed that, in the upper 200 m of the water column, LDOP concentrations ranged from the detection limit (3 nM) to 243 nM, and phosphate concentrations ranged from 5 to 374 nM. The spatial distribution patterns of LDOP were similar to those of phosphate. Most of the depth profiles for LDOP and phosphate showed concentrations were extremely low, <25 nM, between the surface and the deep chlorophyll maximum layer (DCML) and increased below the DCML. Strongly depleted LDOP and phosphate above the DCML suggest that LDOP is actively hydrolyzed under phosphate-depleted conditions and utilized by microbes. 相似文献
35.
Potential and gravity changes raised by point dislocations 总被引:9,自引:0,他引:9
Shuhei Okubo 《Geophysical Journal International》1991,105(3):573-586
36.
Sediment core was collected from Tokyo Bay. The surface enrichment of heavy metals due to human activities is recognized in the sediment. Partitioning of Cu, Zn, Fe and Mn into sulfide, carbonate, organic and silicate fractions has been determined with selective chemical leaching techniques for 210Pb-dated sediment core samples. The heavy metal contents of silicate fractions without exchangeable sites are almost constant against depth in sediment core. However, the Cu, Zn and Mn contents of sulfide, carbonate and organic fractions vary with depth. Most Cu and Zn in the polluted sediment layer are associated with the iron sulfide fraction. 相似文献
37.
The two-dimensional equation of motion containing the pressure gradient and Coriolis force is numerically solved for the wind field in and above the layers of a horizontally homogeneous canopy with a vertical distribution of leaf-area densities. The solution shows that, in the case of descending through the canopy, the wind vector turns with an angle which depends on the profile of leaf-area densities. In particular, for the canopy of a forest consisting of upper layers with higher densities and lower layers with smaller densities, the turning is striking; a secondary maximum in wind profile appears in the lower layers.Variations of the aerodynamic parameters for the flow above the canopy are indicated with respect to the leaf-area density. The roughness length varies in such a manner that a maximum appears in intermediate density values, depending on the shape of the profile of leaf-area density. In the case of very dense canopies, the shearing stress acting on the flow above the canopy is determined by the contribution from only the upper canopy elements, but not by that from the lower parts of the canopy. 相似文献
38.
Shingo Yamada Forecast Division Japan Meteorological Agency Tokyo Japan Shuhei Maeda Administration Division Climate Marine Department Japan Meteorological Agency Tokyo Japan K. Gambo c/o Department of Earth Planetary Physi 《大气科学进展》1997,(1)
NotesonExtended-RangeAtmosphericPredictionintheNorthernHemisphereWinterShingoYamadaForecastDivision,JapanMeteorologicalAgency... 相似文献
39.
40.
Mass balance and sources of mercury in Tokyo Bay 总被引:1,自引:0,他引:1
Masahiro Sakata Kohji Marumoto Masahiro Narukawa Kazuo Asakura 《Journal of Oceanography》2006,62(6):767-775
The mass balance and sources of mercury in Tokyo Bay were investigated on the basis of observations from December 2003 to
January 2005. Estimated input terms included river discharge (70 kg yr−1) and atmospheric deposition (37 kg yr−1), and output terms were evasion (49 kg yr−1), export (13 kg yr−1) and sedimentation (495 kg yr−1). Thus, the outputs (557 kg yr−1) considerably exceeded the inputs (107 kg yr−1). In addition, the imbalance between the inputs and outputs of mercury was much larger than that of other trace metals (Cd,
Cr, Cu, Pb and Zn), which suggests that there are other major inputs of mercury to Tokyo Bay. The mercury concentrations in
rivers correlated significantly with the concentrations of Al and Fe, major components of soil. In Japan, large amounts of
organomercurous fungicides (about 2500 tons as Hg) were used extensively in fields in the past, and most of the mercury was
retained in the soil. In this study, the mercury concentration in rivers was measured primarily in ordinary runoff. These
observations lead to the hypothesis that field soil discharged into stormwater runoff is a major source of mercury in Tokyo
Bay. As a preliminary approach to validating this hypothesis, we measured the concentrations of mercury and other trace metals
in river water during a typhoon. The mercury concentrations in stormwater runoff increased to 16–50 times the mean value in
ordinary runoff, which is much higher than the increases for other metals. This tends to support the hypothesis. 相似文献