Air-sea exchange of mercury in Tokyo Bay     

Masahiro Narukawa  Masahiro Sakata  Kohji Marumoto  Kazuo Asakura 《Journal of Oceanography》2006,62(3):249-257

In Tokyo Bay the concentrations of dissolved gaseous mercury (DGM) in the surface seawater and total gaseous mercury (TGM) over the sea were measured during December 2003, October 2004 and January 2005. Based on these data, the evasional fluxes of mercury from the sea surface were estimated using a gas exchange model. In addition, an automatic wet and dry deposition sampler was used to measure the wet and dry depositional fluxes of mercury from December 2003 to November 2004 at three locations in and near Tokyo Bay. The results indicate that the average DGM and TGM levels of seven locations are 52 ± 26 ng m⁻³ and 1.9 ± 0.6 ng m⁻³, respectively, which shows that the surface seawater in Tokyo Bay is supersaturated with gaseous mercury, leading to an average mercury evasional flux of 140 ± 120 ng m⁻²d⁻¹. On the other hand, the annual average wet and dry depositional fluxes of mercury at three locations were 19 ± 3 μg m⁻²yr⁻¹ and 20 ± 9 μg m⁻²yr⁻¹, respectively. These depositional fluxes correspond to the daily average total depositional flux of 110 ± 20 ng m⁻²d⁻¹. Thus, it is suggested that in Tokyo Bay, the evasional fluxes of mercury are comparable to the depositional fluxes.  相似文献   

Biomass, Abundance, and Vertical Distribution of Micronekton and Large Gelatinous Zooplankton in the Subarctic Pacific and the Bering Sea during the Summer of 1997     

Jun Nishikawa  Shuhei Nishida  Masatoshi Moku  Kiyotaka Hidaka  Kouichi Kawaguchi 《Journal of Oceanography》2001,57(3):361-375

The biomass, abundance, and vertical distribution of micronekton, including enidarians, mysids, euphausiids, decapods, thaliaceans, and fishes, were studied on the basis of samples collected with an 8-m² opening-closing rectangular midwater trawl (RMT-8, mesh size: 4.5 mm) at three stations in the subarctic Pacific (the western subarctic gyre, the central Subarctic, and the Gulf of Alaska) and one station in the oceanic Bering Sea. The total biomass in the 0–1000 m water column ranged from 2.9 to 5.1 gDW m^–2. Except for primary consumers that showed highly variable biomass (thaliaceans and euphausiids), biomass was highest in the oceanic Bering Sea followed by the central (boundary between eastern and western gyres), western gyre, and eastern Gulf of Alaska. The biomass compositions by higher taxa were basically similar between regions: fishes were most dominant, followed by enidarians at all stations, except for the marked predominance of thaliaceans in the Gulf of Alaska. High biomasses of gelatinous animals (31% of overall dry weight), occasionally comparable to those of fishes and crustaceans, suggest their potential importance in the subarctic Pacific. Characteristics in vertical patterns of micronekton biomass common in all stations were: (1) a mesopelagic peak around 500–600 m both day and night, (2) a layer of low biomass in the cold intermediate water and/or in the upper mesopelagic zone, (3) a nighttime shift of biomass to upper layers, and (4) an highly variable biomass of epipelagic/interzonal migrants (euphausiids and thaliaceans).  相似文献   

Impact of the 2011 Tohoku earthquake tsunami on zooplankton community in Otsuchi Bay,northeastern Japan     

Yuichiro Nishibe  Hiroshi Isami  Hideki Fukuda  Shuhei Nishida  Toshi Nagata  Aiko Tachibana  Atsushi Tsuda 《Journal of Oceanography》2016,72(1):77-90

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Occurrence of organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers in deep-sea fishes from the Sulu Sea     

Ramu K  Kajiwara N  Mochizuki H  Miyasaka H  Asante KA  Takahashi S  Ota S  Yeh HM  Nishida S  Tanabe S 《Marine pollution bulletin》2006,52(12):1827-1832

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Contribution of abiogenic and biogenic particles to trace-metal composition of phytoplankton assemblages in seawater of Shimizu Port, Japan     

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   

Comparison of community structures between particle-associated and free-living prokaryotes in tropical and subtropical Pacific Ocean surface waters     

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   

Sensitive determination of enzymatically labile dissolved organic phosphorus and its vertical profiles in the oligotrophic western North Pacific and East China Sea     

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   

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

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Partitioning of heavy metals into mineral and organic fractions in a sediment core from Tokyo Bay     

Yasushi Kitano  Masahiro Sakata  Eiji Matsumoto 《Geochimica et cosmochimica acta》1980,44(9):1279-1285

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   

Numerical studies on the two-dimensional flow in horizontally homogeneous canopy layers     

Junsei Kondo  Shuhei Akashi 《Boundary-Layer Meteorology》1976,10(3):255-272

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