Peridotite xenoliths from the Shiribeshi Seamount,Japan Sea: insights into mantle processes in a back-arc basin     

Yuji Ichiyama  Tomoaki Morishita  Akihiro Tamura  Shoji Arai 《Contributions to Mineralogy and Petrology》2016,171(10):86

  相似文献   

Emergence Patterns of Small Subtidal Arthropods in Relation to Day/Night, Tidal, and Surface/Bottom Factors: Investigations in the Boreal Sea, Japan (Akkeshi, Hokkaido)     

Masayuki Saigusa  Kazushi Oishi  Akihiro Ikumoto  Hiroshi Iwasaki  Michihiro Terajima 《Journal of Oceanography》2000,56(3):295-310

The emergence of small arthropods was studied in the boreal sea, Japan (Akkeshi, Hokkaido). In the shallow subtidal zone, two impeller pumps were set in the surface and bottom waters. The pumps ran continuously for 25 days (22 August-16 September, 1998), and invertebrates were sampled using a nylon net (300 to 500 m in mesh size). The small arthropods collected with the net belonged to 16 orders comprising about 60 taxa. In the dominant 23 taxa, a two-way ANOVA was applied to determine whether there was any significant difference in abundance between day and night and between surface and bottom. While emergence of 15 taxa (65%) was significantly different with regard to the day/night factor, that of the other 8 taxa (35%) was not. As to the difference between the two depths, the distribution of 15 taxa (65%) was significantly different. Furthermore, in 25 taxa for which over 100 specimens were collected in each of the two depths of water, emergence patterns were examined with regard to the synchrony with day/night and tidal cycles. There were various nocturnal patterns, and the strength of the synchrony with the day/night cycle was different for each species or group. Within the same taxa, nocturnal patterns were more clearly manifested in the surface water than in the bottom water. A tidal rhythm of emergence was only seen in zoeas of shrimp. Variations of the emergence patterns of benthic crustaceans are accounted for by a hypothesis that the frequency of swimming during day versus at night is different in each species. On the other hand, the emergence patterns of some zooplankton reflect by the daily rhythm of vertical migration or dispersal in the water column.  相似文献   

长牡蛎(Crassostrea gigas)微卫星克隆快速分离及特性分析   总被引：22，自引：2，他引：22  

李琪  木岛明博 《海洋与湖沼》2004,35(4):364-370

采用磁珠杂交选择和PCR筛选法，从长牡蛎DNA选择片段文库中，快速分离含有微卫星序列的阳性克隆。结果表明，在筛选的200个白色菌落中，56个克隆含有重复次数5以上的微卫星序列，其中41个(20．5％)有随机侧翼区，可以进行引物设计，12个缺乏足够的侧翼序列，3个为中断的微卫星序列。此外，还获得两个小卫星克隆。在获得的微卫星序列中，完全的占54．7％，不完全的占20．8％，复合的占24．5％。除探针中使用的CA重复单元外，还观察到CT、ACT、CGCA、CACT、GACT、GCAC、CCTTA和CCTCA的重复序列。微卫星重复次数主要集中在5-30次之间，占71．7％，最高为60次。本研究中构建的长牡蛎(CA)n富集微卫星文库将为以后开发未知微卫星标记提供帮助。  相似文献   

Primary productivity in a cold water mass and the neighborhood area occurring off Enshu-nada in the late summer of 1989     

Akihiro Shimoto  Satsuki Matsumura 《Journal of Oceanography》1992,48(1):105-115

Primary productivity off Enshu-nada was measured by the¹³C method in September 1989. Primary productivity was estimated in a cold water mass developed off Enshu-nada for the first time. The obtained value was 469 mgC·m^–2·d^–1 and higher than those in the pelagic area of Kuroshio, but equivalent to those in the neritic and the Oyashio areas. It was indicated that cold water mass is the place where organic matter is produced actively. Extremely high chlorophylla of more than 5g·l^–1 were found in the cold water mass. The high productivity was due to high standing crop of phyoplankton. Furthermore, calculated light efficiency and quantum yield showed consistent increase with depth and showed a maximum at 10% light level. Both were larger on the coastal side than those on the oceanic side of the Kuroshio current.  相似文献   

Sequences Characterization of Microsatellite DNA Sequences in Pacific Abalone(Haliotis discus hannai)   总被引：1，自引：0，他引：1  

Kijima Akihiro 《中国海洋大学学报(英文版)》2007,(1)

1 Introduction Microsatellites or simple sequence repeats (SSRs) are tandemly repeated motifs of one to six bases found in all prokaryotic and eukaryotic genomes analysed to date (Zane et al., 2002). Due to their hyper-variable and co-dominant nature, relatively high abundance and random distribution in the genome, microsatellites are among the most efficient class of molecular markers. Such repeats display high polymorphism because of variation in repeat length and can be rapidly analysed t…  相似文献   

Isotopic composition of dissolved inorganic carbon in subsurface sediments of gas hydrate-bearing mud volcanoes, Lake Baikal: implications for methane and carbonate origin   总被引：1，自引：1，他引：0  

Alexey A. Krylov  Oleg M. Khlystov  Akihiro Hachikubo  Hirotsugu Minami  Yutaka Nunokawa  Hitoshi Shoji  Tamara I. Zemskaya  Lieven Naudts  Tatyana V. Pogodaeva  Masato Kida  Gennady V. Kalmychkov  Jeffrey Poort 《Geo-Marine Letters》2010,30(3-4):427-437

We report on the isotopic composition of dissolved inorganic carbon (DIC) in pore-water samples recovered by gravity coring from near-bottom sediments at gas hydrate-bearing mud volcanoes/gas flares (Malenky, Peschanka, Peschanka 2, Goloustnoe, and Irkutsk) in the Southern Basin of Lake Baikal. The δ¹³C values of DIC become heavier with increasing subbottom depth, and vary between ?9.5 and +21.4‰ PDB. Enrichment of DIC in ¹³C indicates active methane generation in anaerobic environments near the lake bottom. These data confirm our previous assumption that crystallization of carbonates (siderites) in subsurface sediments is a result of methane generation. Types of methanogenesis (microbial methyl-type fermentation versus CO₂-reduction) were revealed by determining the offset of δ¹³C between dissolved CH₄ and CO₂, and also by using δ¹³C and δD values of dissolved methane present in the pore waters. Results show that both mechanisms are most likely responsible for methane generation at the investigated locations.  相似文献   

Radiometrically determined skin temperature and scalar roughness to estimate surface heat flux. Part I: Parameterization of radiometric scalar roughness     

Akihiro Kubota  Michiaki Sugita 《Boundary-Layer Meteorology》1994,69(4):397-416

A series of experiments carried out in a pasture field during a growing season, allowed a radiometric determination of the scalar roughness for sensible heatz _oh,r . The values ofz _oh,r are shown to vary over the range of 10^–1–10^–7m both diurnally and seasonally, and an existing theoretical model for the estimation of scalar roughness for sensible heat is found to be inappropriate for the precise estimation ofz _oh,r . To parameterizez _oh,r better, a multiple regression analysis was performed, with predictor candidates such as solar elevation, solar radiationR _s , leaf area index LAI, canopy height, the ratio of the solar radiation and the extraterrestrial radiationR _s /R _e , the ratio of the direct and the total solar radiationR _d /R _s , and the roughness Reynolds number among others. The best regression equation which usesR _s , LAI,R _s /R _e , andR _d /R _s is derived withr=0.75; with smaller numbers of predictors, values ofr tend to deteriorate gradually down tor=0.52 when only one predictor, LAI, was incorporated into the equation.  相似文献   

Magma mixing model for the genesis of middle crust in the Izu–Bonin–Mariana arc: evidence from plutonic rocks in the Mineoka-Setogawa ophiolitic mélange,central Japan     

Yuji Ichiyama  Hisatoshi Ito  Akihiro Tamura  Shoji Arai 《International Geology Review》2020,62(4):503-521

ABSTRACT

A Paleogene accretionary complex, the Mineoka–Setogawa belt is distributed adjacent to the northern portion of the collision zone between Honshu and Izu–Bonin–Mariana (IBM) arcs in central Japan, comprising a mélange of ophiolitic fragments of various sizes. The Eocene-Oligocene plutonic rocks in this belt (gabbro, diorite, and tonalite) have been interpreted as fragments brought from the deep crust beneath the IBM arc through tectonic collisions. The geochemical characteristics of the gabbro and associated basaltic dike are similar to those of the Eocene IBM tholeiitic basalt; thus, the gabbro was likely formed via the crystallization of the Eocene tholeiitic basaltic magmas, which was produced by the partial meltings of a depleted mantle wedge. A comparison with experimental results and geochemical modeling indicates that the tonalite was generated by 10–30% dehydration melting of the gabbro. Actually, Eocene–Oligocene felsic veins, which are coeval with the plutonic rocks, occur in the Mineoka–Setogawa gabbro. Plagioclase crystals in the diorite comprise Ca-rich and -poor parts in a single crystal. Their compositional characteristics are consistent with those of plagioclase in the gabbro and tonalite, respectively. The textures and chemical composition of plagioclase indicate that the diorite was formed by the mixing between mafic and silicic magmas. The whole-rock composition of the diorite also indicates the evidence for the mixing between basaltic magmas which were fractionated to variable degrees and homogeneous silicic magma. The mixing model proposed from the first direct observations of the IBM middle crust exposed on the Mineoka–Setogawa belt is applied to the genesis of the Eocene to present intermediate rocks in the IBM arc. If the continental crust were created at intra-oceanic arc settings such as the IBM arc, the magma mixing model would be one of the most likely mechanisms for the genesis of the continental crust.  相似文献   

Study of the effect of water-soluble fractions of heavy-oil on coastal marine organisms using enclosed ecosystems,mesocosms   总被引：1，自引：0，他引：1  

Ohwada K  Nishimura M  Wada M  Nomura H  Shibata A  Okamoto K  Toyoda K  Yoshida A  Takada H  Yamada M 《Marine pollution bulletin》2003,47(1-6):78-84

Mesocosm facilities composed of 4 experimental and 2 reservoir tanks (1.5 m in diameter, 3.0 m in depth and 5 tons in capacity) made of FRP plastics, were constructed in the concrete fish rearing pond in the Fisheries Laboratory, The University of Tokyo. The water-soluble fraction of Rank A heavy residual oil was formed by mixing 500 g of the oil with 10 l of seawater, which was introduced to the 5000 l-capacity tanks. Experimental Run 4 was conducted from May 31 to June 7, 2000. Oil concentrations in the tanks were 4.5 microg/l called LOW, and 13.5 microg/l, called HIGH tank. Bacterial growth rates very quickly accelerated in the HIGH tank just after the loading of oil which corresponded with a high increase of bacterial cells in the same tank after 2 days. Later, bacterial numbers in HIGH tank rapidly decreased, corresponding with the rapid increase of heterotrophic nano-flagellates and virus numbers on the same day. Sediment traps were deployed at the bottom of the experimental tanks, and were periodically retrieved. These samples were observed both under light microscope and epi-fluorescent microscope with UV-excitation. It was observed that the main components of the vertical flux were amorphous suspended matter, mostly originating from dead phytoplankton and living diatoms. It was further observed from the pictures that vertical transport of oil emulsions were probably conducted after adsorption to amorphous suspended matter and living diatoms, and were settling in the sediment traps at the bottom of the tanks. This means that the main force which drives the soluble fraction of oil into bottom sediment would be vertical flux of such amorphous suspended particles and phytoplankton. Further incubation of the samples revealed that the oil emulsions were degraded by the activity of autochtonous bacteria in the sediment in aerobic condition.  相似文献   

Melting of enstatite from 13 to 18 GPa under hydrous conditions     

Akihiro Yamada  Tetsuo Irifune 《Physics of the Earth and Planetary Interiors》2004,147(1):45-56

Experiments on MgSiO₃ enstatite were conducted in the pressure range from 13 to 18 GPa under hydrous conditions in order to clarify the effect of water on the melting phase relations of enstatite at pressures corresponding to the Earth’s mantle transition zone. In some previous experiments [Geol. Soc. Am. Bull. 79 (1968) 1685; Phys. Earth Planet. Inter. 85 (1994) 237], incongruent melting behavior to form Mg₂SiO₄ forsterite and SiO₂ enriched liquid up to 5 GPa was observed, and congruent melting behavior at pressures up to 12 GPa was observed. Under hydrous conditions, we found that the melting reaction changes from congruent to incongruent at around 13.5 GPa. Liquid formed above 13.5 GPa is enriched in MgO component relative to MgSiO₃ because it coexists with stishovite (SiO₂). Moreover, the solidus temperature decreases drastically at around 13.5 GPa, in unison with the change in the melting reaction. The solidus temperature is about 1400 °C at 13 GPa, but approximately 900 °C at 15 GPa. Our results show that the liquidus phase changes from clinoenstatite to stishovite with increasing pressure and water content above 13.5 GPa. MgSiO₃ enstatite is one of the major constituent minerals in the Earth’s mantle, and it is expected that MgO-enriched liquid will be generated in the transition zone if water is present.  相似文献