Seagrasses from the Nansei Islands, Southern Japanese Archipelago: species composition, distribution and biogeography     

John Kuo  Ziyusei Kanamoto  Hitoshi Iizumi  Keiko Aioi  & Hiroshi Mukai 《Marine Ecology》2006,27(4):290-298

The Nansei Islands in the southern Japanese Archipelago have 15 taxa of seagrasses from seven genera within three families. Seagrasses in this region grow on coral sands or coral debris in shallow reefs and on sandy or muddy substrata in the shallow areas of bays and inlets. Certain Halophila species grow in deep water off some islands. Enhalus acoroides only reaches to Ishigaki I. with winter sea water temperature (WST) at 23 °C, while Okinawa I. (WST at 21.6 °C) is the northern biogeographic limit for Halophila decipiens, H. okinawensis, H. major and H. gaudichaudii. Amami‐oshima I. (WST at 20.7 °C) is the northern border for Thalassia hemprichii, H. minor, H. ovalis, Cymodocea serrulata, Cymodocea rotundata, Syringodium isoetifolium, Halodule uninervis and Halodule pinifolia. Halophila mikii the sole seagrass collected from Yakushima I. (WST at 19.3 °C), is of volcanic origin. The distribution of tropical seagrasses in the Nansei Islands is clearly associated with the warm Kuroshio Current, WST and habitat availability. Zostera japonica is the only temperate species occurring in the region. Meadows of Z. japonica, H. ovalis and Halodule pinifolia have disappeared from certain localities in the Archipelago, due probably to human activities and natural siltation.  相似文献   

Seasonal and interannual variability of sea surface chlorophyll a concentration in the Japan/East Sea (JES)     

Keiko Yamada  Joji Ishizaka  Sinjae Yoo  Hyun-cheol Kim  Sanae Chiba 《Progress in Oceanography》2004,61(2-4):193

Seasonal and interannual variability of chlorophyll a concentration in the Japan/East Sea (JES) was detected spatially by ocean color satellite remote sensing. Start timing of the spring bloom was different spatially. The spring bloom started at the subpolar front and southward of it in March, northward of subpolar front, along the Primorye coast and off Hokkaido in April and in the middle of the Japan Basin in May. The start of the spring bloom showed interannual variability that corresponded with the wind speed in the area. The spring bloom in 1998 and 2002 appeared about four weeks earlier than in 1997, 1999 and 2001, and it corresponded with weak winds that can lead to an early development of the thermocline. The bloom was late in 1999 and 2001 in the Japan Basin and along the Primorye coast, and in the southern area in 2000. It corresponded with stronger wind stress that delayed seasonal thermocline formation. The bloom along the Primorye coast appeared later in 1999, and it corresponded with stronger wind stress, and at the same time, it seemed to be related with the delay of melting of sea ice in Mamiya Strait. The fall bloom appeared from early October to early December, and it did not have a clear temporal transition. The area where chlorophyll a concentration exceeded 0.8 μg l⁻¹ was wider in the western area than in the eastern area every year. The magnitude of the fall bloom was different between years, but it did not show a correlation with average wind speed in fall. Those results indicated that the timing of the seasonal bloom in the JES is largely affected by the variability of global climate such as ENSO events.  相似文献   

Spatial and Temporal Variability of Satellite Primary Production in the Japan Sea from 1998 to 2002   总被引：1，自引：0，他引：1  

Keiko?Yamada  Joji?IshizakaEmail author  Hiroshi?Nagata 《Journal of Oceanography》2005,61(5):857-869

The spatial and seasonal variability of primary production in the Japan Sea from 1998 to 2002 was estimated using a satellite primary production model. A size-fractionated primary production model was validated by in situ primary production data measured in the Japan Sea. Estimated primary production and in situ primary production showed a good positive correlation. Estimated primary production showed spatial variability. Annual primary production levels were 170, 161, 191 and 222 gC m⁻²year⁻¹ at the Russian coast, in the middle of the Japan Basin, the southeastern area and the southwestern area, respectively. It was higher to the south around 40°N than to the north, and higher in the western area than in the eastern one. Peaks of primary production appeared twice, in spring and fall, in the southern area, while a single peak appeared in the northern area. Primary production along the Russian coast was higher than in other areas during summer. The spring bloom contributed 42% to the annual primary production in these four areas. Furthermore, estimated primary production showed an interannual variability that was largest in spring. Primary production in fall also showed interannual variability, especially in the middle of the Japan Basin and the southwestern area. This corresponded mainly to the size of the phytoplankton bloom in each year. Winter convection by wind and the depth of nutrient-rich, cold subsurface water underlying the Tsushima Current may contribute to the nutrient supply to upper layer and interannual variations of primary production in spring.  相似文献   

苏鲁超高压变质带胡家林超镁铁质岩成因及构造意义   总被引：1，自引：1，他引：0  

谢志鹏  王建  HATTORI Keiko  薛传东  钟军伟  王泽利 《岩石学报》2018,34(6):1539-1556

胡家林超镁铁质杂岩体产于苏鲁超高压变质带中部,纯橄岩和(石榴)单斜辉石岩呈不连续透镜体产于蛇纹石化橄榄岩中。纯橄岩遭受了部分蛇纹石化(烧失量=6.6%～13.2%),全岩富集强相容元素(Ni、Cr、Co)和Ir族PGE(IPGE;Ir、Os、Ru)及高IPGE/PPGE值,亏损Al、Ti、V,具高Mg~#橄榄石(Fo=91.7～92.4)和高Cr~#(0.68～0.76)尖晶石。纯橄岩高耐熔地球化学及矿物化学特征和古老的大陆岩石圈地幔相一致,表明其原岩来源于弧前地幔,代表了华北克拉通古老的大陆岩石圈地幔残留。(石榴)单斜辉石岩全岩呈相对低含量的强相容元素(Cr、Ni、Co)和IPGE,高含量的Al、Ti、V和流体迁移元素(Sr、Pb和Ba),球粒陨石标准化REE配分图呈明显"上凸"型,具低Mg~#橄榄石(Fo=76.6～76.8)和低Al_2O_3(2.76%)和高SiO_2(54.56%～56.87%)的单斜辉石。全岩组成和矿物化学表明其原岩为俯冲带内超镁铁质火成堆晶岩,最初岩浆由地幔岩高程度部分熔融的熔体和俯冲带中富H_2O流体和/或熔体构成。(石榴)单斜辉石岩原岩曾被地幔流带入扬子大陆俯冲板片和上覆地幔楔之间的俯冲通道,经历了超高压变质作用和生成大量石榴石。(石榴)单斜辉石岩在折返过程中,与大陆岩石圈地幔楔剥离的蛇纹石化橄榄岩及纯橄岩相结合,形成超镁铁质杂岩体,整体被低密度的俯冲板片(主要由花岗质片麻岩和变质沉积岩组成)裹挟,折返至地壳浅部。  相似文献   

Subduction of mantle wedge peridotites: Evidence from the Higashi-akaishi ultramafic body in the Sanbagawa metamorphic belt   总被引：1，自引：0，他引：1  

Keiko  Hattori  Simon  Wallis  Masaki  Enami  Tomoyuki  Mizukami 《Island Arc》2010,19(1):192-207

The Higashi-akaishi garnet-bearing ultramafic body in the Sanbagawa metamorphic belt, Southwest Japan, represents a rare example of oceanic-type ultrahigh-pressure metamorphism. The body of 2 km × 5 km is composed mostly of anhydrous dunite with volumetrically minor lenses of clinopyroxene-rich rocks. Dunite samples contain high Ir-type platinum group elements (PGE) and Cr in bulk rocks, high Mg and Ni in olivine, and high Cr in spinel. On the other hand, clinopyroxene-rich rocks contain low concentrations of Ir-type PGE and Cr, high concentrations of fluid-mobile elements in bulk rocks, and low Ni and Mg in olivine. Clinopyroxene is diopsidic with low Al₂O₃. The compositions of bulk rocks and mineral chemistry of spinel, olivine, and clinopyroxene suggest that the olivine-dominated rocks are residual mantle peridotites after high degrees of influx partial melting, and that the clinopyroxene-rich rocks are cumulates of subduction-related melts. Thus, the Higashi-akaishi ultramafic body originated from the interior of the mantle wedge, most likely the forearc upper mantle. It was then incorporated into the Sanbagawa subduction channel by a mantle flow, and underwent high pressure metamorphism to a depth greater than 100 km. Such a strong active flow in the mantle wedge is likely facilitated by the lack of serpentinites along the interface between the slab and the overlying mantle, as it was too hot for serpentine. These unusually hot conditions and strong active mantle flow may reflect conditions in the earliest stage of development of subduction, and may have been maintained by massive upwelling and subsequent eastward flow of asthenospheric mantle in the northeastern Asian continent in Cretaceous time when the Sanbagawa belt began to form.  相似文献   

吉林东部汪清新生代玄武岩中地幔包体的矿物化学：对该地区岩石圈地幔形成过程的启示   总被引：1，自引：0，他引：1  

宋樾  王建  刘金霖  谢志鹏  Keiko H.HATTORI 《地学前缘》2013,20(5):75-86

在对吉林汪清新生代玄武岩中橄榄岩包体进行全岩主、微量元素分析的基础上,重点分析了矿物的主、微量元素含量,讨论了华北克拉通东北缘与兴蒙造山带结合部位陆下岩石圈地幔所经历的部分熔融作用和地幔交代作用。橄榄石的Fo、单斜辉石以及尖晶石的Mg#和Cr#均表明该地区陆下岩石圈地幔相对饱满。对地幔橄榄岩透辉石微量元素模拟计算证实,汪清陆下岩石圈地幔经历了1%~3%的部分熔融作用,并遭受后期硅酸盐熔体交代作用。这些地幔特征与中国东部其他地区新生代主体岩石圈相似。研究结果证明,吉林汪清中、新生代以来岩石圈性质的转变是在汇聚板块构造体制下通过“拆沉作用”实现的。  相似文献   

Modeling seasonal variations of ocean and sea ice circulation in the Beaufort and Chukchi Seas： A model-data fusion study     

Kohei Mizobata  Walter Johnson  Koji Shimada  Moto Ikeda 《极地研究(英文版)》2008,19(2):168-184

A 3.8-kin Coupled Ice-Ocean Model （C1OM） was implemented to successfully reproduce many observed phenomena in the Beaufort and Chukchi seas, including the Bering-inflow-originated coastal current that splits into three branches： Alaska Coastal Water （ACW） , Central Channel, and Herald Valley branches. Other modeled phenomena include the Beaufort Slope Current （BSC） , the Beaufort Gyre, the East Siberian Current （ ESC）, mesoscale eddies, seasonal landfast ice, sea ice ridging, shear, and deformation. Many of these downscaling processes can only be captured by using a high-resolution CIOM, nested in a global climate model. The seasonal cycles for sea ice concentration, thickness, velocity, and other variables are well reproduced with Solid validation by satellite measurements. The seasonal cycles for upper ocean dynamics and thermodynamics are also well reproduced, which include the formation of the cold saline layer due to the injection of salt during sea ice formation, the BSC, and the subsurface upwelling in winter that brings up warm, even more saline Atlantic Water along the shelfbreak and shelf along the Beaufort coast.  相似文献   

Geochemical and Microbiological Analysis of Sambe Hot Springs,Shimane Prefecture,Japan     

Keiko Sasaki  Yoshitaka Uejima  Atsushi Sakamoto  Qianqian Yu  Junichiro Ishibashi  Naoko Okibe  Tsuyoshi Hirajima 《Resource Geology》2013,63(2):155-165

Microbiological contribution to the formation of the manganese deposits in Sambe hot springs, Shimane, was investigated in combination with water chemistry, characterization of sediments and microbial community structure. Analysis of bacterial and fungal community structure based on DNA extracted from a Mn‐oxidizing enrichment culture indicated close matches with Pseudomonas putida, Phoma sp. and Plectosphaerella cucumerina, all Mn‐oxidizing microorganisms. These sediments were poorly crystalline and formed at neutral pH values, which is characteristic of biogenic precipitates. The EPMA results demonstrated a positive correlation between Mn and Ba contents in well‐crystalline Mn oxide grains. Substantial Ba contents were observed inside Mn oxide grains. These findings indicated that Ba contents in sediments are influenced by not only aqueous Ba²⁺ concentrations but also crystallinity of biogenic birnessite. Barium would be incorporated in birnessite during biomineralization.  相似文献   

Behavior of Siderophile and Chalcophile Elements in the Subcontinental Lithospheric Mantle beneath the Changbaishan Volcano,NE China   总被引：1，自引：0，他引：1  

WANG Jian  LIU Jinlin  HATTORI Keiko  XU Wenliang  XIE Zhipeng  SONG Yue 《《地质学报》英文版》2012,86(2):409-421

The mantle xenoliths in the Quaternary ChangbaishanVolcano in southern Jilin Province contain spinel-facies lherzolites. The equilibration temperatures for these samples range from 902oC to 1064oC based on the two-pyroxene thermometer of Brey and K?hler (1990), and using the oxybarometry of Nell and Wood (1991), the oxidation state was estimated from FMQ-1.32 to -0.38 with an average value of FMQ-0.81 (n?=?8), which is comparable to that of abyssal peridotites and the asthenospheric mantle. The fO2 values of peridotites, together with their bulk rock compositions (e.g., Mg#, Al2O3, CaO, Ni, Co, Cr) and mineral compositions (e.g., Mg# of olivine and pyroxene, Cr# [=Cr/[Cr+Al]] and Mg# [=Mg/[Mg+Fe2+] of spinel), suggest that the present-day subcontinental lithospheric mantle (SCLM) beneath the Changbaishan Volcano most likely formed from an upwelling asthenosphere at some time after the late Mesozoic and has undergone a low degree of partial melting. The studied lherzolite xenoliths show low concentrations of S, Cu, and platinum group elements (PGE), which plot a flat pattern on primitive-mantle normalized diagram. Very low concentrations in our samples suggest that PGEs occur as alloys or hosted by silicate and oxide minerals. The compositions of the studied samples are similar to those of peridotite xenoliths in the Longgang volcanic field (LVF) in their mineralogy and bulk rock compositions including the abundance of chalcophile and siderophile elements. However, they are distinctly different from those of peridotite xenoliths in other areas of the North China Craton (NCC) in terms of Cu, S and PGE. Our data suggest that the SCLM underlying the northeastern part of the NCC may represent a distinct unit of the newly formed lithospheric mantle.  相似文献   

Ground motion characteristics and shaking damage of the 11th March 2011 M w9.0 Great East Japan earthquake     

Katsuichiro Goda  Antonios Pomonis  Siau Chen Chian  Mark Offord  Keiko Saito  Peter Sammonds  Stuart Fraser  Alison Raby  Joshua Macabuag 《Bulletin of Earthquake Engineering》2013,11(1):141-170

A catastrophic M _w9.0 earthquake and subsequent giant tsunami struck the Tōhoku and Kanto regions of Japan on 11th March 2011, causing tremendous casualties, massive damage to structures and infrastructure, and huge economic loss. This event has revealed weakness and vulnerability of urban cities and modern society in Japan, which were thought to be one of the most earthquake-prepared nations in the world. Nevertheless, recorded ground motion data from this event offer invaluable information and opportunity; their unique features include very strong short-period spectral content, long duration, and effects due to local asperities as well as direction of rupture/wave propagation. Aiming at gaining useful experience from this tragic event, Earthquake Engineering Field Investigation Team (EEFIT) organised and dispatched a team to the Tōhoku region of Japan. During the EEFIT mission, ground shaking damage surveys were conducted in Sendai, Shirakawa, and Sukagawa, where the Japan Meteorological Agency intensity of 6+ was observed and instrumentally recorded ground motion data were available. The damage survey results identify the key factors for severe shaking damage, such as insufficient lateral reinforcement and detailing in structural columns from structural capacity viewpoint and rich spectral content of ground shaking in the intermediate vibration period range from seismic demand viewpoint. Importantly, inclusion of several ground motion parameters, such as nonlinear structural response, in shaking damage surveys, can improve the correlation of observed ground motion with shaking damage and therefore enhance existing indicators of potential damage.  相似文献