Particulate peptidoglycan in seawater determined by the silkworm larvae plasma (SLP) assay     

Akira Shibata  Kouichi Ohwada  Masakazu Tsuchiya  Kazuhiro Kogure 《Journal of Oceanography》2006,62(1):91-97

Peptidoglycan (PG) is a biopolymer found exclusively in the cell wall of bacteria. Recent chemical analysis of particulate organic matter suggests that a major amount of the muramic acid, an amino sugar present only in PG, could not be accounted for in terms of bacterial cells (Benner and Kaiser, 2003); however, data on particulate PG is quite sparse. In the present study, conducted in 1996, the PG was examined at 5 sampling sites in the northwestern Pacific Ocean, and in natural seawater cultures. Particulate PG, which was concentrated using a 96-well filtration plate equipped with Durapore filters (pore size, 0.22 μm), was measured by the silkworm larvae plasma (SLP) assay. The PG concentration generally decreased with depth and correlated significantly with bacterial abundance throughout the entire water column. However, the ratio of particulate PG to bacterial abundance varied with depth. The average ratio was 0.61 ± 0.53 (average ± SD, n = 40) between 50 and 2000 m, which agreed with the bacterial cellular PG content from 0.63 to 1.1 fg cell⁻¹ obtained in seawater cultures. On the other hand, the ratios of PG to bacteria from the surface to 50 m (3.7 ± 2.6, n = 29) and below 2,000 m (2.1 ± 1.7, n = 7) were significantly higher than that between 50 and 2,000 m. These results may suggest that, in the surface and deep layers, a significant fraction of particulate PG was present in bacterial detritus, whereas this fraction was reduced in the middle layer.  相似文献   

Numerical study of the summer temperature decrease induced by the enhancement of estuarine circulation in Fukuoka Bay     

Kazuhiro Aoki  Atsuhiko Isobe 《Journal of Oceanography》2006,62(2):207-217

The Princeton Ocean Model with realistic bottom topography has been used to investigate the summer temperature decrease in the past 25 years in Fukuoka Bay. The vertical mixing of the model is expressed by a scheme that effectively includes the influences of interannual variations of tidal currents and wind. The results show that the historical temperature decrease in summer has been caused by tidal currents and wind weakening in the past 25 years in Fukuoka Bay. The weakening of tidal currents and wind gives rise to weakening of the vertical mixing, and to enhancement of the estuarine circulation in the bay. The enhancement of the estuarine circulation activates the inflow of open-ocean water toward Fukuoka Bay. Coastal water in summer has therefore tended to be colder and more saline in the past 25 years. This interannual variation in coastal waters is called “open-oceanization” in this study. On the basis of the numerical model, it is anticipated that the temperature will decrease by 0.2°C in the next 25 years in Fukuoka Bay if the tide and wind weaken persistently as in the present bay.  相似文献   

Application of Atomic Force Microscopy to Observation of Marine Bacteria   总被引：3，自引：0，他引：3  

Tomohiko Nishino  Eiko Ikemoto  Kazuhiro Kogure 《Journal of Oceanography》2004,60(2):219-225

The atomic force microscopy (AFM) is a recently developed, bench-top instrument that can image the surface structures of biological specimens at high resolution with simultaneous measurement of their size. This paper describes the application of AFM to marine bacteria. Both natural and cultured bacteria were retained on a filter or placed on glass, washed, air-dried and observed by AFM. The instrumental condition, the choice of suitable filter, effect of fixation and filtration, comparison with epifluorescent microscopic (EFM) count, and the size and shape of bacterial cells were investigated. An Isopore filter was best for concentration and subsequent observation because of its surface flatness. Cross section images showed that both rod and coccoid cells were flattened, the former usually having a two-humped shape. Bacterial cells were differentiated from non-living particles based on their cross section shape and size. Bacterial counts by AFM and EFM showed good agreement. Although size measurement is easily done by the instrument, AFM tends to overestimate the size of microspheres. More work is thus needed on the size measurement of living organisms. Because AFM easily provides images of natural bacterial cells at high magnification, it can be used as a new tool to study the fine structures of marine bacteria. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Use of an optical oxygen sensor to measure dissolved oxygen in seawater     

Hiroshi Hasumoto  Tsuneo Imazu  Toshiaki Miura  Kazuhiro Kogure 《Journal of Oceanography》2006,62(1):99-103

The use of an optical oxygen sensor to measure dissolved oxygen in seawater was investigated. The sensor is based on the dynamic quenching of an oxygen-sensitive fluorochrome embedded in the tip. Dissolved oxygen in seawater samples collected from eight stations at depths ranging from 3000 to 6000 m was analyzed both with the optical sensor and by the Winkler titration method. The two sets of data did not differ significantly. The stability and simplicity of the method and the good agreement of the results with those of the titration method indicate that the sensor would be useful for fieldwork.  相似文献   

Ecologic and taxonomic diversification in the Mesozoic brackish-water bivalve faunas in Japan, with emphasis on infaunalization of heterodonts     

Yasuo Kondo  Takeshi Kozai  Naoki Kikuchi  Kazuhiro Sugawara 《Gondwana Research》2006,10(3-4):316-327

Mesozoic brackish-water bivalve faunas in Japan diversified in three steps: at the beginning of the Early Jurassic, Early and Late Cretaceous. The Hettangian Niranohama Fauna in northeastern Honshu represents the establishment of a heterodont-dominated brackish-water fauna that persisted until the early Late Cretaceous. No similar composition is known from the Triassic. The infauna consists mostly of non-siphonate and some short-siphonate heterodonts, while the epifauna is represented by diverse pteriomorphian families. In the Early Cretaceous Tetori Group in central Honshu, the long-siphonate heterodonts Tetoria (Corbiculidae) and the semi-infaunal soft-bottom oyster Crassostrea appeared. The evolutionary diversification of the latter, known as the most important element of modern brackish-water faunas, may thus originate at that time. In the early Late Cretaceous (Cenomanian) of the Goshoura and Mifune Groups in west Kyushu, several euryhaline deep-burrowing heterodont families, such as Veneridae and Tellinidae, further diversified in the brackish and marine environments. The Late Cretaceous is characterized by massive shell biolithic beds in which large Crassostrea species are common, a feature common for Cenozoic brackish-water faunas. The long-term changes in the composition of the brackish-water faunas in Japan represents thus an evolutionary record, irrespective of the severe physiological and environmental conditions imposed on the highly conservative nature of the fauna.  相似文献   

Jurassic Dextral and Cretaceous Sinistral Movements Along the Hida Marginal Belt     

Kazuhiro Tsukada 《Gondwana Research》2003,6(4):687-698

The Hida marginal belt (HMB), which consists of various kinds of fault-bound blocks, is located between the continental massif of the Hida belt and the Mesozoic accretionary complex of the Mino belt in Central Japan. Detailed field investigation reveals that the HMB had grown through the two different movements, i.e., Jurassic dextral and Cretaceous sinistral movements. The Jurassic dextral ductile shear zones run in the southern marginal part of the Hida belt and the northern part of the HMB, whereas the Cretaceous sinistral cataclastic shear zones occur in the southern part of the HMB and the northern marginal part of the Mino belt. Geologic map and field evidence seem to suggest that the Jurassic dextral movement form the fault-bound blocks of the HMB to form the basic structure of the Hida marginal belt, i.e., formation of the ‘proto-HMB.’ Following the dextral movement, the sinistral one restructured the ‘proto-HMB’ to complete the present feature of the Hida marginal belt. The Cretaceous sinistral movement might result in the sinistral collision between the proto-HMB and the Mino belt.  相似文献   

Formation and shortening deformation of a back-arc rift basin revealed by deep seismic profiling, central Japan   总被引：1，自引：0，他引：1  

Hiroshi Sato  Takaya Iwasaki  Shinji Kawasaki  Yasutaka Ikeda  Nobuhisa Matsuta  Tetsuya Takeda  Naoshi Hirata  Taku Kawanaka   《Tectonophysics》2004,388(1-4):47

The northern Fossa Magna (NFM) basin is a Miocene rift system produced in the final stages of the opening of the Sea of Japan. It divides the major structure of Japan into two regions, with north-trending geological structures to the NE of the basin and EW trending structures to the west of the basin. The Itoigawa-Shizuoka Tectonic Line (ISTL) bounds the western part of the northern Fossa Magna and forms an active fault system that displays one of the largest slip rates (4–9 mm/year) in the Japanese islands. Deep seismic reflection and refraction/wide-angle reflection profiling were undertaken in 2002 across the northern part of ISTL in order to delineate structures in the crust, and the deep geometry of the active fault systems. The seismic images are interpreted based on the pattern of reflectors, the surface geology and velocities derived from refraction analysis. The 68-km-long seismic section suggests that the Miocene NFM basin was formed by an east dipping normal fault with a shallow flat segment to 6 km depth and a deeper ramp penetrating to 15 km depth. This low-angle normal fault originated as a comparatively shallow brittle/ductile detachment in a high thermal regime present in the Miocene. The NFM basin was filled by a thick (>6 km) accumulation of sediments. Shortening since the late Neogene is accommodated along NS to NE–SE trending thrust faults that previously accommodated extension and produce fault-related folds on their hanging wall. Based on our balanced geologic cross-section, the total amount of Miocene extension is ca. 42 km and the total amount of late Neogene to Quaternary shortening is ca. 23 km.  相似文献   

Kinematic analysis of sinistral cataclastic shear zones along the northern margin of the Mino Belt, central Japan   总被引：1，自引：0，他引：1  

Masakazu Niwa  Kazuhiro Tsukada  Shiro Tanaka 《Journal of Asian Earth Sciences》2005,24(6):787

In this paper, cataclastic shear zones along the northern margin of the Mino Belt, central Japan are described, and the significance of the shearing in the tectonic evolution of SW Japan is examined. The Mino Belt in SW Japan is composed of accretionary complexes of Jurassic to Early Cretaceous age. Field investigation revealed that remarkable cataclastic shear zones trending east to northeast run along the northern margin of the Mino Belt. Closely spaced cleavage is developed in these shear zones. Lineation on the cleavage plunges at shallow to moderate angles. Deformation structures (e.g. composite planar fabric and asymmetric structure of clasts) in the sheared rocks clearly indicate a sinistral sense of shear. The shearing ceased by latest Cretaceous time, because the sheared rocks are overlain by unsheared Upper Cretaceous volcanic rocks. The sinistral shearing may be closely related to Cretaceous sinistral movement along the eastern margin of Asia. Sinistral shearing along the northern margin of the Mino Belt can be considered as a key for re-examining the tectonic development of SW Japan.  相似文献   

Least squares and integral methods for the spherical harmonic analysis of theSq-field     

Koji Kawasaki  S. Matsushita  J. C. Cain 《Pure and Applied Geophysics》1989,131(3):357-370

Spherical harmonic coefficients (SHCs) for the daily magnetic variation fields (solar and lunar) and the main field of the earth are usually estimated by the method of least squares applied to a truncated spherical harmonic series. In this paper, an integral method for computing the SHCs for the solar quiet daily magnetic variation fieldSq is described and applied toSq data for May and June 1965. TheSq SHCs thus derived are then compared with the results obtained using both unweighted and weighted versions of the least squares method. The weighting used tends to orthogonalize the least squares terms. The integral and weighted least squares results agree closely for terms up to order 4 and degree 30, but both disagree considerably for the higher degree terms with the results of the unweighted least squares. Errors introduced by the numerical integration can be shown to be small, hence the disagreement between integral and unweighted least squares coefficient sets arises from improper weighting. Also, it is concluded that discrepancies between the geomagnetic northward and eastward component-derived coefficient sets arise from either time-dependent external sources that produce non-local-time, based fields or nonpotential sources and not from truncation of the spherical harmonic series as has previously been suggested.Deceased.  相似文献   

Structural change of GeO2 under pressure     

S. Kawasaki  O. Ohtaka  T. Yamanaka 《Physics and Chemistry of Minerals》1994,20(8):531-535

Pressure-induced amorphization of α-quartz type GeO₂ was studied with a newly developed X-ray diffraction system which consists of a 4-circle goniometer and a curved position sensitive detector. Single-crystal diffraction was measured under pressurs up to 7.3 GPa at room temperature in order to investigate pretransitional phenomena. Diffraction intensity and line width of the diffraction profiles showed no remarkable change up to 5.9 GPa. However, no sharp diffraction line was observed at pressures over 6.5 GPa. The bulk modulus at 0.1 MPa and its pressure derivative of α-quartz type GeO₂ were determined to be K _T =32.8(3.3) GPa and K′ _T =6.0(2.0), respectively. In situ microscopic observations of the amorphization transformation was also performed. The large volume change due to amorphization was observed and estimated to be about 10%.  相似文献