Habitability analyses of aquatic bacteria     

Md. Nurul Haider  Masahiko Nishimura  Minoru Ijichi  Ching-chia Yang  Wataru Iwasaki  Kazuhiro Kogure 《Journal of Oceanography》2018,74(2):197-207

Habitability is defined as an ability of an organism to inhabit different environments. Habitability of organisms, however, cannot be inferred from analyses such as a whole genome or community structures. A recently developed database, the MetaMetaDB, gives us information from what kind of environments one particular 16S rRNA sequence data has ever been obtained, and thus enables us to infer the habitability of the bacterium in question. In order to check the applicability of this database to study the habitability of aquatic bacteria, samples collected at two Naka River stations, one estuarine station from Naka River Estuary, two coastal stations at Oarai in Ibaraki Prefecture, Japan and one station in the Kuroshio Current of the western North Pacific were examined. The phylotypes were tracked against the MetaMetaDB and it was reasonably found that the low-salinity stations were dominated by sequences with “freshwater and groundwater”, “human” and “wastewater” habitat identities, while the high-salinity stations were dominated by those with a “marine” identity. The phylotypes of low-salinity stations with a particular habitat identity were absent or rare in the high-salinity stations and vice versa. The MetaMetaDB also showed that sequences of Cyanobacteria or related phylogenetic groups may be present in the human gut, as well as the probable distribution of the relatives (ancestors/descendants/siblings) of some bacteria. These overall findings proved that the MetaMetaDB is useful as a new tool to infer microbial habitability and it gives us new information on the possible origin and ecology of microorganisms in the environments.  相似文献   

Decadal-scale variation in COD and DIN dynamics during the summer in the inner area of the Ariake Sea,Japan     

Yuichi Hayami  Naoki Fujii 《Journal of Oceanography》2018,74(6):551-563

More than 30 years of chemical oxygen demand (COD) and dissolved inorganic nitrogen (DIN) data for the inner area of the Ariake Sea were analyzed with a box model to show the changes in the average seasonal budget and the decadal-scale variation during the summer. The COD peaked in August and March on average. This summertime peak can be explained by an enhanced riverine load and increased primary production. The peak in March suggested additional organic matter production. There were also two peaks in DIN concentration on average: a summertime peak that could be explained by an enhanced riverine load, and a peak in December that was more complicated to explain. From the 1970s to the early 1990s, the bottom water in this area became increasingly hypoxic due to increased COD during the summer, even though there were minimal increases in terrestrial COD and nutrient loads and there were tidal flats covering a widespread area during this period. The increase in COD was caused by increased net ecosystem production, which was due to enhanced primary production induced by an increased freshwater residence time and decreased bivalve grazing. There was a negative feedback control in which hypoxia progressively increased, leading to declines in bivalve biomass, which in turn decreased the grazing pressure limiting primary production, meaning that primary production increased and the area became even more hypoxic. The net DIN production decreased during the 1980s and the 1990s. This was consistent with the change in net ecosystem production according to the COD.  相似文献   

Theoretical and experimental investigation of nickel isotopic fractionation in species relevant to modern and ancient oceans     

Toshiyuki Fujii  Frédéric Moynier  Minori Abe 《Geochimica et cosmochimica acta》2011,75(2):469-7643

Nickel plays a central role as an enzyme co-factor in the metabolism of methanogenic Archaea. Methanogens can fractionate Ni isotopes during assimilation, opening the possibility of using the stable isotopic composition of Ni as a biomarker. However, other sources of Ni isotopic variations need to be evaluated before one can establish Ni isotopes as an unambiguous tracer of methanogenesis in the rock record. Equilibrium exchange of Ni between the different species present in the ocean is a potential source of isotopic fractionation. Through controlled laboratory experiments and theoretical calculations, we quantify equilibrium Ni isotope fractionation between different species relevant to the modern and ancient ocean: Ni(H₂O)₆²⁺, Ni(H₂O)₁₈²⁺, NiOH(H₂O)₅⁺, Ni(OH)₂(H₂O)₄, NiCl(H₂O)₅⁺, cis-NiCl₂(H₂O)₄, trans-NiCl₂(H₂O)₄, NiHS(H₂O)₅⁺, Ni(HS)₂(H₂O)₄, NiSO₄(H₂O)₄, NiHCO₃(H₂O)₄⁺, NiCO₃(H₂O)₄, and organic ligands (crown ether and oxalic acid). The magnitude of ligand-controlled Ni isotopic fractionation, approximately 1.25‰/amu (2.5‰ for the ⁶⁰Ni/⁵⁸Ni ratio), is similar to that previously measured in cultures of methanogenic Archaea.  相似文献   

Experimental study on prevention of acid mine drainage by silica coating of pyrite waste rocks with amorphous silica solution   总被引：1，自引：1，他引：0  

Masahiko Bessho  Takaaki Wajima  Takuro Ida  Takashi Nishiyama 《Environmental Earth Sciences》2011,64(2):311-318

Acid mine drainage (AMD) is a widespread environmental problem associated with working and abandoned mining operations. It results from the microbial oxidation of pyrite in the presence of water and air, affording an acidic solution that contains toxic metal ions. Pyrite microencapsulation, utilizing silica coating, is a novel approach for controlling AMD that has been shown to be very effective in controlling pyrite oxidation. The roles of the solution pH and silica concentration in the formation mechanism for the AMD-preventing coating were investigated. A silica coating can be formed from silica solution at pH 7, at which the amount of Fe eluted from pyrite into the solution is small. No coating was formed at other pH values, and the amounts of eluted Fe were larger than at pH 7, especially at pH 11. The silica coating forms from 2,500 to 5,000 mg/L silica solutions, but not from 0 or 1,000 mg/L silica solutions. The coating formation rate was slower in the 2,500 mg/L silica solution than in the 5,000 mg/L silica solution. The formation of silica coating on pyrite surfaces depends on three main steps: formation of Fe(OH)₃ on the surface of pyrite, reaction between Fe(OH)₃ and silicate in the solution on the pyrite surface, and growth of the silica layer on the first layer of silica. The best pH condition to enable these steps was around 7, and the silica coating formation rate can be controlled by the concentration of silica.  相似文献   

3-D internal architecture of methane hydrate-bearing turbidite channels in the eastern Nankai Trough, Japan     

Satoshi Noguchi  Naoyuki Shimoda  Osamu Takano  Nobutaka Oikawa  Takao Inamori  Tatsuo Saeki  Tetsuya Fujii 《Marine and Petroleum Geology》2011,28(10):1817-1828

The reservoir architecture of methane hydrate (MH) bearing turbidite channels in the eastern Nankai Trough, offshore Japan is evaluated using a combination of 3-D seismic and well data. On the 3-D seismic section, the MH-bearing turbidite channels correspond to complex patterns of strong seismic reflectors, which show the 3-D internal architecture of the channel complex. A seismic-sequence stratigraphic analysis reveals that the channel complex can be roughly classified into three different stages of depositional sequence (upper, middle, and lower). Each depositional sequence results in a different depositional system that primarily controls the reservoir architecture of the turbidite channels. To construct a 3-D facies model, the stacking patterns of the turbidite channels are interpreted, and the reservoir heterogeneities of MH-bearing sediments are discussed. The identified channels at the upper sequence around the β1 well exhibit low-sinuosity channels consisting of various channel widths that range from tens to several hundreds of meters. Paleo-current flow directions of the turbidite channels are typically oriented along the north-northeast-to-south-southwest direction. High-amplitude patterns were identified above the channels along the north-to-south and north-northeast-to-south-southeast directions. These roughly coincide with the paleo-current flow of the turbidite channels. An interval velocity using high-density velocity analysis shows that velocity anomalies (>2000 m/s) are found on the northeastern side of the turbidite channels. The depositional stage of the northeastern side of the turbidite channels exhibits slightly older sediment stages than the depositional stages of the remaining channels. Hence, the velocity anomalies of the northeastern side of the channels are related to the different stages of sediment supply, and this may lead to the different reservoir architectures of the turbidite channels.  相似文献   

Laboratory Enrichment of Radioactive Assemblages and Estimation of Thorium and Uranium Radioactivity in Fractions Separated from Placer Sands in Southeast Bangladesh     

Takayuki Sasaki  Mohammad Rajib  Masafumi Akiyoshi  Taishi Kobayashi  Ikuji Takagi  Toshiyuki Fujii  Md. Mashrur Zaman 《Natural Resources Research》2015,24(2):209-220

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Fractured Rock Permeability as a Function of Temperature and Confining Pressure     

A. K. M. Badrul Alam  Yoshiaki Fujii  Daisuke Fukuda  Jun-ichi Kodama  Katsuhiko Kaneko 《Pure and Applied Geophysics》2015,172(10):2871-2889

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Mapping the change of coral reefs using remote sensing and in situ measurements: a case study in Pangkajene and Kepulauan Regency,Spermonde Archipelago,Indonesia     

La Ode Muhammad Yasir Haya  Masahiko Fujii 《Journal of Oceanography》2017,73(5):623-645

As elsewhere in Indonesia, local inhabitants in the Pangkajene and Kepulauan (PANGKEP) Regency, Spermonde Archipelago area and along the south-west coast of Sulawesi traditionally regard the coral reefs as their livelihood source. Since human activities as well as natural disturbances pose major threats to the coral reefs, these livelihoods may also be at risk. Currently, no comprehensive information on the status and condition of coral reefs in this area is available for this resource management. We determined the changes of coral reef habitat over a period of 20 years from 1994 to 2014 using a satellite Landsat multi-temporal image substantiated with in situ measurement data collected in 2014. The spectral value of coral reefs was extracted from multi-temporal Landsat imagery data, while the diffuse attenuation coefficient of water was obtained by using statistical analysis between the ratio of live coral cover and the spectral value of the visible bands. By using the unsupervised classification integrated with the data ground truth, it is stated that there has been a decline in live coral cover over a period of 20 years from 7716 ha in 1994 to 4236 ha in 2014, with a degradation rate of 174 ha/year. Based on the results, the ratio of the coral cover in the coral reef transects varied from the average of 24% for live corals to 96% for coral rubbles, implying the degraded status of coral reefs in the study area.  相似文献   

Nonlinear behavior of high-damping rubber bearings under horizontal bidirectional loading: full-scale tests and analytical modeling     

Masashi Yamamoto  Shigeo Minewaki  Harumi Yoneda  Masahiko Higashino 《地震工程与结构动力学》2012,41(13):1845-1860

Horizontal bidirectional loading tests are conducted for real-sized high-damping rubber (HDR) bearings with diameters of 700 mm (HDR700) and 1300 mm (HDR1300). The hysteresis loops of these bearings under bidirectional horizontal loadings are compared with those under unidirectional loadings. The results show that the bearing force measurement in the primary direction of loading increases when there is displacement in the orthogonal direction. Unusually, the maximum restoring force in the orthogonal direction to the primary loading direction occurs near zero displacement. On the basis of the observations of the restoring forces, a rate-independent model is proposed. This model simulates well the test results under both bidirectional loading and unidirectional loading. It can reproduce the irregular restoring forces characteristics around zero displacement as described above. Bidirectional loading induced twist deformation in the HDR bearings that increased local shear strains. This phenomenon results in an early failure as observed in HDR700. The additional shear strain is estimated based on the twist deformation measured by video image analysis. The comparison of the nominal total shear stress demonstrates that the increase of shear stress because of bidirectional loading occurs when the average shear strain is larger than about 200%. The larger the shear strain, the greater the bidirectional effect. It is shown that the nominal total shear stress of average strain of 350% under bidirectional circular loading pattern is approximately the same as the average shear strain of 400% under unidirectional loading. This means that the average shear strain of 350% under a bidirectional circular loading corresponds to a local shear strain of 400%. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Evolution of Mount Fuji,Japan: Inference from drilling into the subaerial oldest volcano,pre‐Komitake     

Mitsuhiro Yoshimoto  Toshitsugu Fujii  Takayuki Kaneko  Atsushi Yasuda  Setsuya Nakada  Akikazu Matsumoto 《Island Arc》2010,19(3):470-488

A buried, old volcanic body (pre‐Komitake Volcano) was discovered during drilling into the northeastern flank of Mount Fuji. The pre‐Komitake Volcano is characterized by hornblende‐bearing andesite and dacite, in contrast to the porphyritic basaltic rocks of Komitake Volcano and to the olivine‐bearing basaltic rocks of Fuji Volcano. K‐Ar age determinations and geological analysis of drilling cores suggest that the pre‐Komitake Volcano began with effusion of basaltic lava flows around 260 ka and ended with explosive eruptions of basaltic andesite and dacite magma around 160 ka. After deposition of a thin soil layer on the pre‐Komitake volcanic rocks, successive effusions of lava flows occurred at Komitake Volcano until 100 ka. Explosive eruptions of Fuji Volcano followed shortly after the activity of Komitake. The long‐term eruption rate of about 3 km³/ka or more for Fuji Volcano is much higher than that estimated for pre‐Komitake and Komitake. The chemical variation within Fuji Volcano, represented by an increase in incompatible elements at nearly constant SiO₂, differs from that within pre‐Komitake and other volcanoes in the northern Izu‐Bonin arc, where incompatible elements increase with increasing SiO₂. These changes in the volcanism in Mount Fuji may have occurred due to a change in regional tectonics around 150 ka, although this remains unproven.  相似文献