Population genetic diversity and structure of a dominant tropical seagrass,Cymodocea rotundata,in the Western Pacific region          下载免费PDF全文

Dan M. Arriesgado  Hiroyuki Kurokochi  Yuichi Nakajima  Yu Matsuki  Wilfredo H. Uy  Miguel D. Fortes  Wilfredo L. Campos  Kazuo Nadaoka  Chunlan Lian 《Marine Ecology》2016,37(4):786-800

Cymodocea rotundata is an ecologically important tropical pioneer seagrass species distributed in the Indo‐Pacific region. The population genetic diversity and structure of this species were analysed at 46 sites spanning the Philippines, Ryukyu Islands (northern limit) and Hainan Island, by using microsatellite simple sequence repeat (SSR) markers. Analyses revealed the persistence of C. rotundata likely relies on local population dynamics and fitness influenced by environmental gradients, with sexual reproduction prevalent in the Philippines while the Ryukyu and Hainan populations were predominantly established by clonal spread. Analysis of molecular variance showed significant genetic differentiation (P < 0.001) among three geographic regions: the Philippines, Ryukyu and Hainan. Furthermore, the mean fixation index value was very high (F_ST = 0.36), indicating poor dispersal potential or limited gene flow. Allelic richness and heterozygosity of C. rotundata was comparable in the Philippines and Ryukyu Islands populations. More private alleles were found in the Philippines and excess heterozygotes in the Ryukyu Islands. STRUCTURE analysis revealed that the Ryukyu and Hainan populations were mosaics of admixed alleles of individuals from the Philippines. An assignment test suggested that recruitment occurs from the Northeast Philippines to Ryukyu Islands. These results suggest that the Philippine populations are tropical seagrass hotspots and perhaps the origin of the populations in the Ryukyu and Hainan Islands. This scenario is most likely driven by the Kuroshio Current and island integration events during plate tectonic activities. The Philippine Archipelago is considered of high importance for conservation objectives and management plan of seagrasses. Likewise, the Ryukyu Islands are also important in terms of conserving regional diversity because locally adapted genotypes have important evolutionary potential in the face of environmental change.  相似文献   

Factors controlling typhoons and storm rain on the Korean Peninsula during the Little Ice Age   总被引：1，自引：0，他引：1  

Kota Katsuki  Dong-Yoon Yang  Koji Seto  Moriaki Yasuhara  Hiroyuki Takata  Masashi Otsuka  Toshimichi Nakanishi  Yoonyeol Yoon  In-Kwon Um  Richard C. W. Cheung  Boo-Keun Khim  Kaoru Kashima 《Journal of Paleolimnology》2016,55(1):35-48

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Latitudinal change in benthic foraminiferal fauna by ITCZ movement along the ~131°W transect in the equatorial Pacific Ocean     

Hiroyuki Takata  Chan Min Yoo  Hyung Jeek Kim  Boo-Keun Khim 《Ocean Science Journal》2016,51(4):655-663

Modern and fossil benthic foraminifera were examined from nine surface sediments and two piston cores along the ~131°W transect in the equatorial Pacific Ocean. This study was conducted to clarify the biotic response of abyssal benthic foraminifera during the last 220 ka to changes in the seasonal extent of the Intertropical Convergence Zone (ITCZ). The abundance of modern benthic foraminifera was high at stations between the equator and 6°N, whereas it was low at stations north of 6°N, which is generally consistent with the latitudinal CaCO₃ distribution of surface sediments. The northward increase of Epistominella exigua from the equator to ~6°N is similar to the seasonal variations in chlorophyll-a concentrations in the surface water and ITCZ position along ~131°W. This species was more common at core PC5103 (~6°N) than at core PC5101 (~2°N) after ~130 ka, when the Shannon-Wiener diversity (H’) between the two cores started to diverge. Hence, the presentday latitudinal difference in benthic foraminifera (E. exigua and species diversity) between ~2°N and ~6°N along ~131°W has been generally established since ~130 ka. According to the modern relationship between the seasonality of primary production and seasonal ITCZ variations in the northern margin of the ITCZ, the latitudinal divergence of benthic foraminiferal fauna between ~2°N and ~6°N since ~130 ka appear to have been induced by more distinct variations in the seasonal movement of ITCZ.  相似文献   

The multiple chronological techniques applied to the Lake Suigetsu SG06 sediment core,central Japan     

Richard A. Staff  Takeshi Nakagawa  Gordon Schlolaut  Michael H. Marshall  Achim Brauer  Henry F. Lamb  Christopher Bronk Ramsey  Charlotte L. Bryant  Fiona Brock  Hiroyuki Kitagawa  Johannes van der Plicht  Rebecca L. Payne  Victoria C. Smith  Darren F. Mark  Alison Macleod  Simon P. E. Blockley  Jean‐Luc Schwenninger  Pavel E. Tarasov  Tsuyoshi Haraguchi  Katsuya Gotanda  Hitoshi Yonenobu  Yusuke Yokoyama  Suigetsu Project Members 《Boreas: An International Journal of Quaternary Research》2013,42(2):259-266

The varved sediment of Lake Suigetsu (central Japan) provides a valuable opportunity to obtain high‐resolution, multi‐proxy palaeoenvironmental data across the last glacial/interglacial cycle. In order to maximize the potential of this archive, a well‐constrained chronology is required. This paper outlines the multiple geochronological techniques being applied – namely varve counting, radiocarbon dating, tephrochronology (including argon–argon dating) and optically stimulated luminescence (OSL) – and the approaches by which these techniques are being integrated to form a single, coherent, robust chronology. Importantly, we also describe here the linkage of the floating Lake Suigetsu (SG06) varve chronology and the absolute (IntCal09 tree‐ring) time scale, as derived using radiocarbon data from the uppermost (non‐varved) portion of the core. This tie‐point, defined as a distinct (flood) marker horizon in SG06 (event layer B‐07–08 at 1397.4 cm composite depth), is thus derived to be 11 255 to 11 222 IntCal09 cal. years BP (68.2% probability range).  相似文献   

Attenuation of compressional waves in peridotite measured as a function of temperature at 200 MPa   总被引：3，自引：0，他引：3  

Hiroki Sato  I. Selwyn Sacks  Tsutomu Murase  Gregory Muncill  Hiroyuki Fukuyama 《Pure and Applied Geophysics》1988,128(1-2):433-447

A technique has been developed to determine attenuation in rocks at high temperature using a gas-media, high-pressure apparatus. A pulse transmission technique and a spectral ratio method are used to study compressional seismic properties of rocks. Seismic waves are transmitted to and from the sample through buffer rods of mullite. The effect of seismic wave reflections within the sample assembly are cancelled out by taking ratios of the spectra measured at different temperatures. In order to obtain good signal-to-noise ratio for resolving the attenuation at high pressure and temperature, special care is taken in the sample assembly and the ultrasonic coupling between the sample, buffer rods and transducers. A very tight connection of the sample-buffer rod-transducer is essential for obtaining high frequency signals (>300 kHz) at high temperature. A small mass is attached to each outside end of the transducer to drive low frequency signals (<250 kHz) into the sample. Before attenuation measurements, the sample and the buffer rods are tightly compacted in a platinum tube at high pressure and room temperature to ensure pressure seal of the sample assembly. The frequency range of measurement covers 50 to 450 kHz for the sample. Attenuation is very small in the buffer rod compared to the sample for the entire temperature range of the study. Because of the small attenuation, a wide frequency band of 50 kHz to 3.2 MHz can be covered for investigating the attenuation in the buffer rod. The technique has been used to measure attenuation at high confining pressure, and temperatures including sub- and hyper-solidus of upper mantle rocks. Therefore, effects of partial melting on attenuation can be studied.The method is applied to the attenuation measurement in a peridotite as a function of temperature to 1225°C at 200 MPa confining pressure. At high temperature, signal amplitude decays more rapidly at high frequency than at low frequency, from which attenuation (andQ) can be determined using a spectral ratio method. No frequency dependence ofQ is resolved for both the sample and the buffer rod over the entire temperature and frequency ranges of the measurement. The results show thatQ decreases rapidly with increasing temperature even in the temperature range below the solidus of peridotites. Such temperature sensitivity ofQ is probably more useful to probe thermal structure in the upper mantle than that of conductivity at temperatures below the solidus. The results in this study are compared with available seismic velocity, electrical conductivity and solidus data for peridotites, suggesting that there is no discontinuous change in both mechanical and electrical properties of peridotites at the solidus temperature. Even at hypersolidus temperatures, it appears that velocity drops and conductivity increases continuously (not abruptly) with increasing melt fraction. This implies that mechanical and electrical properties of the upper mantle will gradually change at the boundary where the geotherm crosses the solidus.  相似文献   

Summary of the fossil record of pinnipeds of Japan, and comparisons with that from the eastern North Pacific     

Shigeo  Miyazah Hideo  Horkawa Naoki  Kohno Kiyoharu  Hirota Masaichi  Kimura Yoshkazu  Hasegawa Yukimitsu  Tomida Lawrence G.  Barnes Clayton E.  Ray 《Island Arc》1994,3(4):361-372

Abstract The fossil pinniped record of the North Pacific Ocean includes both Phocidae and Otariidae ( sensu lato ), extends from the Late Oligocene to the Late Pleistocene, is taxonomically diverse, and is constantly becoming more complete owing to additional important discoveries. The earliest and most diverse fossil pinnipeds in the North Pacific are otariids, the phocids not appearing until the latest Pliocene. The theoretical center of otariid pinniped evolutionary history has been considered by some to be in the eastern North Pacific. New materials from the western North Pacific, however, including representatives of the subfamilies Enaliarctinae, Imagotariinae, Odobeninae and Otariinae, indicate that pinniped evolutionary patterns were basin-wide phenomena, and that a more complete record undoubtedly would reveal numerous trans-Pacific distributions. This would be expected considering the distributions of living species. The paucity of fossil Phocidae and their absence from pre-Pliocene deposits are consistent with theories that the family primarily evolved outside the North Pacific.  相似文献   

Seismic,petrologic, and geodetic analyses of the 1999 dome-forming eruption of Guagua Pichincha volcano,Ecuador     

Alexander Garcia-Aristizabal  Hiroyuki Kumagai  Pablo Samaniego  Patricia Mothes  Hugo Yepes  Michel Monzier 《Journal of Volcanology and Geothermal Research》2007

Guagua Pichincha, located 14 km west of Quito, Ecuador, is a stratovolcano bisected by a horseshoe-shaped caldera. In 1999, after some months of phreatic activity, Guagua Pichincha entered into an eruptive period characterized by the extrusion of several dacitic domes, vulcanian eruptions, and pyroclastic flows. We estimated the three-dimensional (3-D) P-wave velocity structure beneath Guagua Pichincha using a tomographic inversion method based on finite-difference calculations of first-arrival times. Hypocenters of volcano-tectonic (VT) earthquakes and long-period (LP) events were relocated using the 3-D P-wave velocity model. A low-velocity anomaly exists beneath the caldera and may represent an active volcanic conduit. Petrologic analysis of eruptive products indicates a magma storage region beneath the caldera, having a vertical extent of 7–8 km with the upper boundary at about sea level. This zone coincides with the source region of deeper VT earthquakes, indicating that a primary magma body exists in this region. LP swarms occurred in a cyclic pattern synchronous with ground deformation during magma extrusions. The correlation between seismicity and ground deformation suggests that both respond to pressure changes caused by the cyclic eruptive behavior of lava domes.  相似文献   

A Simple Single-Layer Urban Canopy Model For Atmospheric Models: Comparison With Multi-Layer And Slab Models   总被引：26，自引：7，他引：26  

Hiroyuki Kusaka  Hiroaki Kondo  Yokihiro Kikegawa  Fujio Kimura 《Boundary-Layer Meteorology》2001,101(3):329-358

We developed a simple, single-layer urban canopy model, and comparedit to both multi-layer and slab models. Our single-layer model has thefollowing features: (a) It is a column model of energy and momentumexchange between an urban surface and the atmosphere, (b) it includesthe influence of street canyons, which are parameterized to representthe urban geometry, (c) it includes shadowing from buildings andreflection of radiation, and (d) it estimates both the surfacetemperatures of, and heat fluxes from, three surface types: roof, wall,and road. In the simulation of the single-layer model, the roof washottest during the daytime, but coolest from midnight to early morning.This is consistent with output from the multi-layer model and fieldobservations at a residential area on a clear, summer day. The diurnalvariation of the energy budget from the single-layer model agrees wellwith that from the multi-layer model. Our single-layer model'sperformance is nearly that of a multi-layer model for studyingmesoscale heat islands. Nevertheless, it is simply parameterized,and thus easily included in larger-scale atmospheric models. The slabmodel has the largest nighttime cooling rate of the three models. Toovercome this, it needs more adjustments than for the canopy models.  相似文献   

Micellar-Enhanced Ultrafiltration and Air Stripping for Surfactant-Contaminant Separation and Surfactant Reuse   总被引：2，自引：0，他引：2  

K. Michelle Lipe  David A. Sabatini  Mark A. Hasegawa  Jeffrey H. Harwell 《Ground Water Monitoring & Remediation》1996,16(1):85-92

Micellar-enhanced ultrafiltration (MELT) and air stripping were evaluated for surfactant-contaminant separation and surfactant recovery. Two linear alkyl diphenyloxide disulfonate (DPDS) surfactants were evaluated with the contaminants naphthalene and trichloroethylene. A separation model developed from micellar partitioning principles showed a good correlation to batch MEUF studies, whereas flux analysis highlighted concentration polarization effects in relation to hydrophobe length. MEUF effectively concentrated the surfactant-contaminant system (93 to 99 percent retention); however, this did not result in surfactant-contaminant separation. Batch and continuous flow air stripping models were developed based upon air/water ratio, surfactant concentration, and Micellar partitioning; model predictions were validated by experimental data. Sensitivity analyses illustrated the decline in contaminant-surfactant separation with increasing surfactant concentration (e.g., TCE removal efficiency declines from 83 percent to 37 percent as C-16 DPDS concentration increases from 0 to 55 mM). This effect is greater for more hydrophobic contaminants (naphthalene vs. TCE) and surfactants with greater solubilization potential (C16-DPDS vs. C-12 DPDS). The resulting design equations can account for this effect and thus properly size air strippers to achieve the desired removal efficiency in the presence of surfactant micelles. Proper selection and design of surfactant-contaminant separation and surfactant recovery systems are integral to optimizing surfactant-enhanced subsurface remediation.  相似文献   

Sulfate reduction using methane in sediments beneath a bathyal “cold seep” giant clam community off Hatsushima Island, Sagami Bay, Japan     

Toshiyuki Masuzawa  Nobuhiko Handa  Hiroyuki Kitagawa  Minoru Kusakabe 《Earth and Planetary Science Letters》1992,110(1-4):39-50

Two sandy sediment cores (Cores D227-120 and D380) were collected from inside a deep-sea giant clam (Calyptogena soyoae) community off Hatsushima Island, western Sagami Bay, central Japan (35°59.9′N, 139°13.6′E; 1160 m deep) and a muddy sediment core (Core D227-202) was obtained from outside the community by the submersibleShinkai 2000. The chloride concentration of the pore waters is constant vertically and sulfate reduction using sedimentary organic matter occurs in Core D227-202 (21 cm long). The chloride concentrations are lower by 7% at the 7.5–9 cm depth in Core D227-120 (9 cm long) and by 3% at the 11–12 cm depth in Core D380 (16 cm long) than those of the overlying bottom waters in the cores from inside of the community. Sulfate concentration decreases remarkably and dissolved inorganic carbon, alkalinity, ammonium-N, and hydrogen sulfide concentrations increase significantly with increasing depth in Core D380.δ³⁴S values of sulfate ions increase from +20.5 to +35.3‰ andδ¹³C values of dissolved inorganic carbon decrease drastically from −7.0 to −45‰ with increasing depth from the top to the bottom of the core, although theδ¹³C values of the organic carbon of the sediments are−23.7 ± 0.9‰ in Core D380. These results indicate that sulfate reduction using methane is active within the sediments just beneath the living clams and that the hydrogen sulfide produced can be used by endosymbiotic sulfur oxidizing bacteria living in the gills ofC. soyoae in the community.  相似文献