Contribution of different functional groups to the diet of major predatory fishes at a seagrass meadow in northeastern Japan     

Katsumasa Yamada  Masakazu Hori  Yoshiyuki Tanaka  Natsuki Hasegawa  Masahiro Nakaoka 《Estuarine, Coastal and Shelf Science》2010

We examined the variation in habitat use and diet of three dominant fish species (Myoxocephalus brandti, Pholidapus dybowskii, and Pholis crassispina) in a seagrass meadow in the Akkeshi-ko estuary in northeastern Japan, where broad and dense Zostera marina beds exist, using a semi-quantitative census of the fishes and analyses of their stomach contents. Differences among the three fish species in the temporal variation in abundance of each age class (mainly 1- and 2-year age classes) indicated that the temporal pattern of utilization of the seagrass meadow were different among them. In the semi-quantitative dietary analysis, two prey categories, i.e., taxonomic group (order and suborder) and functional group, were used to explain the variation in prey composition with size-dependent changes. The six prey functional groups were classified based on the ecological traits of the prey, i.e., trophic level, size, and life type (habitat and behavior). Ontogenetic shifts in prey of the three fish species could be fully explained by a combination of the two prey categories, and not by the use of only one category (taxonomic or functional group). The pattern of ontogenetic shifts in prey differed among the fish species and size (age) classes. These results indicate that segregation of habitat (seagrass meadow) and prey group (taxonomic and functional group) is performed among the three species, which may contribute to their coexistence in this estuary.  相似文献   

Preliminary report on Lower Jurassic radiolaria of Gondwana origin from the Kawhia coast, New Zealand     

R. S. Hori  Y. Aita  J. A. Grant-Mackie   《Island Arc》1996,5(2):104-113

Abstract Well-preserved radiolarians from the Newcastle Group in southwest Kawhia, New Zealand, constitute the first record of Lower Jurassic radiolarians from in situ deposits in high latitudes of the Southern Hemisphere on the margin of Gondwana. The radiolarians were extracted from carbonate nodules from five horizons in the Rewarewa Formation and the lower part of the Arawhero Formation, in the Murihiku Terrane. The radiolarian-bearing sequence, which lies within the upper part of the type section of the local Aratauran Stage, is roughly datable as Hettangian-Sinemurian from rare ammonite occurrences. The radiolarian assemblages consist, on average, of 80–90% spumellarians and 10–20% nassellarians. Spumellarians include species of the following genera: Archaeotriastrum, Crucella, Emiluvia (?) Homeoparo-riaella, Orbictilifomaa, Pantanellium, Paronaella (?), Pseudocrucella, PseIIdoheliodiscus, Spon-gostaurus and Spongotrochus. Nassellarians are composed of species of Ragotum, Bipedis, Droltus, Jams (?) Perispyridium (?) Raoultius, Riedelius, Saitoum and Thetis. From data of Lower Jurassic radiolarian faunas of Europe, North America and Japan, the New Zealand fauna shows stronger affinity with those of the European Tethys such as Turkey (e.g. De Wever 1982) and the Northern Alps (Kozur & Mostler 1990) than with faunas from other areas of the circum-Pacific. This connection between the European Tethyan and New Zealand faunas is not well explained by presently accepted continental reconstructions (Smith et al. 1994) for the Early Jurassic.  相似文献   

Control of incised-valley fill stacking patterns by accelerated and decelerated sea-level rise: the Changjiang example during the last deglaciation     

K. Hori  Y. Saito  Q. Zhao  P. Wang 《Geo-Marine Letters》2002,22(3):127-132

The evolution of paleo-Changjiang incised-valley fills in relation to step-like, postglacial sea-level rises is presented, based on sedimentary facies analyses and ¹⁴C age dating on three sediment cores. Timing of rapid transgressions deduced from the succession of incised-valley fills correlate well with Barbados's very rapid, sea-level rise periods. By contrast, estuarine deposits aggraded actively, and the coastline did not retreat markedly during the Younger Dryas (YD) cooling event when the rising rate decelerated considerably relative to stages before and after the YD.  相似文献   

Two modes of climatic control in the Holocene stalagmite record from the Japan Sea side of the Japanese islands          下载免费PDF全文

Tomomi Sone  Akihiro Kano  Kenji Kashiwagi  Taiki Mori  Tomoyo Okumura  Chuan‐Chou Shen  Masako Hori 《Island Arc》2015,24(3):342-358

The Holocene stalagmite FG01 collected at the Fukugaguchi Cave in Itoigawa, central Japan provides a unique high‐resolution record of the East Asian winter monsoon. Because of the climate conditions on the Japan Sea side of the Japanese islands, the volume of precipitation during the winter is strongly reflected in the stalagmite δ¹⁸O signal. Examination of the carbon isotopes and the Mg/Ca ratio of FG01 provided additional information on the Holocene climate in Itoigawa, which is characterized by two different modes separated at 6.4 ka. Dripwater composition and the correlation between the δ¹³C and Mg/Ca data of FG01 indicate the importance of prior calcite precipitation (PCP), a process that selectively eliminated ¹²C and calcium ions from infiltrating water from CO₂ degassing and calcite precipitation. In an earlier period (10.0–6.4 ka), an increase in soil pCO₂ associated with warming and wetting climate trends was a critical factor that enhanced PCP, and resulted in an increasing trend in the Mg/Ca and δ¹³C data and a negative correlation between the δ¹³C and δ¹⁸O profiles. A distinct peak in the δ¹³C age profile at 6.8 ka could be a response to an increase of approximately 10% in C4 plants in the recharge area. At 6.4 ka, the climate mode changed to another, and correlation between δ¹⁸O and δ¹³C became positive. In addition, a millennial‐scale variation in δ¹⁸O and pulsed changes in δ¹³C and Mg/Ca became distinct. Assuming that δ¹⁸O and PCP were controlled by moisture in the later period, the volume of precipitation was high during 6.0–5.2, 4.4–4.0, and 3.0–2.0 ka. In contrast, the driest interval in Itoigawa was during 0.2–0.4 ka, and broadly corresponds to the Little Ice Age.  相似文献   

Radio Bursts Associated with Flare and Ejecta in the 13 July 2004 Event     

S. Pohjolainen  K. Hori  T. Sakurai 《Solar physics》2008,253(1-2):291-303

We investigate coronal transients associated with a GOES M6.7 class flare and a coronal mass ejection (CME) on 13 July 2004. During the rising phase of the flare, a filament eruption, loop expansion, a Moreton wave, and an ejecta were observed. An EIT wave was detected later on. The main features in the radio dynamic spectrum were a frequency-drifting continuum and two type II bursts. Our analysis shows that if the first type II burst was formed in the low corona, the burst heights and speed are close to the projected distances and speed of the Moreton wave (a chromospheric shock wave signature). The frequency-drifting radio continuum, starting above 1 GHz, was formed almost two minutes prior to any shock features becoming visible, and a fast-expanding piston (visible as the continuum) could have launched another shock wave. A possible scenario is that a flare blast overtook the earlier transient and ignited the first type II burst. The second type II burst may have been formed by the same shock, but only if the shock was propagating at a constant speed. This interpretation also requires that the shock-producing regions were located at different parts of the propagating structure or that the shock was passing through regions with highly different atmospheric densities. This complex event, with a multitude of radio features and transients at other wavelengths, presents evidence for both blast-wave-related and CME-related radio emissions.  相似文献   

Current state of integrated earthquake simulation for earthquake hazard and disaster   总被引：1，自引：0，他引：1  

Muneo Hori  Tsuyoshi Ichimura 《Journal of Seismology》2008,12(2):307-321

This paper presents the current state of integrated simulation for earthquake hazard and disaster. This simulation takes advantage of the macro–micro analysis method; this method estimates an earthquake’s strong motion with high spatial and temporal resolution, using the bounding medium theory to obtain optimistic and pessimistic estimates of expected strong motion distribution and the singular perturbation expansion that results in an efficient multi-scale analysis. Integrated earthquake simulation calculates seismic responses for all structures in a target area, inputting simulated strong ground motion to a structure analysis method that is plugged into the system by means of a wrapper; a suitable method, linear or nonlinear, is chosen depending on the type of the structure. The results of all simulations are visualized so that residences and government officials can share a common recognition of earthquake hazard and disaster. Two examples of this integrated earthquake simulations are presented; one is made by plugging nonlinear structure analysis methods into the system, and the other is made for an actual city, the computer model of which is constructed with the help of available geographical information systems.  相似文献   

Physical criterion to evaluate seismic activity associated with the seismic cycle of great interplate earthquakes     

Takane Hori  Yoshiyuki Kaneda 《Journal of Seismology》2004,8(2):225-233

A new criterion is introduced to judge if the vicinity of the source region of a great interplate earthquake is in an active period. It is based on the stress change caused by the great earthquake. A region is regarded as being in an active period of seismicity if the occurrence rate of earthquakes on faults in the stress shadow of the great earthquake is significantly higher than in the early stage of the seismic cycle, and if the stressing rate of these faults is sufficiently low. This criterion was applied to the seismicity in the central part of southwest Japan before and after the 1944 Tonankai and 1946 Nankai earthquakes. The results show that before the 1944 Tonankai earthquake, the region was in an active period from at least 1927.The region was in a quiet period for almost50 years after the 1946 Nankai earthquake.Data after 1995 show that the region is once more in an active period of seismicity preceding the next great interplate earthquakes along the Nankai trough,although the total number of earthquakes has not yet significantly increased. Our results indicate that earthquake probability in the central part of southwest Japan will become high in the coming decades until the next great interplate earthquakes along the Nankai trough.  相似文献