The Role of Suspended Oyster Culture on Nitrogen Cycle in Hiroshima Bay   总被引：1，自引：0，他引：1  

Putth Songsangjinda  Osamu Matsuda  Tamiji Yamamoto  Narasimmalu Rajendran  Hajime Maeda 《Journal of Oceanography》2000,56(2):223-231

The predominance of bivalves affects the cycle of materials in the coastal ecosystem. In the present study, the role of suspended oyster culture on the nitrogen cycle was demonstrated for the northern Hiroshima Bay. The nitrogen cycle was considered as two systems, (1) the primary production (PP) system and (2) the oyster culture (OC) system. The results show that about 26% of N productivity was supplied to process by cultured oysters in the OC system. This process varies seasonally due to the seasonal variations of PON, physiological activities and biomass of oysters. The N processing rates were found to be high in summer and low in winter. The biodeposition and excretion of N in the OC system are 3.0 and 2.1 ton N d^–1, while the natural sedimentation rate and N regeneration in the PP system are 8.3 and 18.0 ton N d^–1, which indicates that the PP system is a major system regenerating N in the water column. The release of total dissolved N from the bottom to the water column is about 8.3 ton N d^–1. The amount of N harvested as oyster product was about 1.3 ton N d^–1, which is about 10% of daily N loading in north Hiroshima Bay. According to the N cycle developed in the present study, the results suggest the significant role of suspended oyster culture on the nitrogen cycle in Hiroshima Bay. In addition, our results indicate that oyster production was efficiently harvested, suggesting that oyster culture could probably be used as a tool to remove N from Hiroshima Bay.  相似文献   

GIS and quantitative geography     

Keiji Yano 《GeoJournal》2000,52(3):173-180

The purpose of this paper is to explore the development of the GIS revolution within the field of geography in the 1980s and 1990s, taking into consideration the influence of external and internal factors on disciplinary change. Geography is rapidly changing by the impact of external factors on geographical research and also as a consequence of economic recession and cutbacks in higher education. Most geography departments in universities have tried to approach this impact by promoting or shifting to human geography as an applied science, and by offering relevant skills through GIS as an approach to contemporary problems. It is concluded that quantitative geography is essential for the further expansion of GIS within geography and also for the survival of geography. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Numerical analysis of effects of tidal variations on storm surges and waves   总被引：2，自引：0，他引：2  

Soo Youl Kim  Tomohiro Yasuda  Hajime Mase 《Applied Ocean Research》2008,30(4):311-322

This study examines the effects of tides on surges, wave setups and waves, in terms of tidal amplitudes and phases, by using a coupled numerical model of Surge, WAve and Tide (called as SuWAT). The SuWAT model, composed of depth integrated nonlinear shallow water equations and Simulating WAves Nearshore (SWAN) model, is able to simultaneously run with an arbitrary number of nested domains by using the Message Passing Interface. The results for an idealized case indicate that surge and wave setup are increased in the phase of low water and decreased in the high water phase; on the other hand, waves change in a reverse manner. Such changes are enhanced by large tidal variations. The conventional method (e.g., surge plus tide independently) has the possibility of overestimation for the total water level. The hindcast results for Typhoon Ewiniar in 2006 show that the run with tides is more accurate 10% than that without tides in coastal areas of Korea. The nested scheme improves the accuracy up to 40% for the prediction of water levels in the simulations. It is shown that the present coupled model, SuWAT, is capable of predicting both water levels and waves under storm events with reasonable accuracy against the observations.  相似文献   

Further characterization of carbonaceous materials in Hayabusa‐returned samples to understand their origin     

Masayuki Uesugi  Motoo Ito  Hikaru Yabuta  Hiroshi Naraoka  Fumio Kitajima  Yoshinori Takano  Hajime Mita  Yoko Kebukawa  Aiko Nakato  Yuzuru Karouji 《Meteoritics & planetary science》2019,54(3):638-666

Carbonaceous materials in the sample catcher of the Hayabusa spacecraft were assigned as category 3 particles. We investigated the category 3 particles with a suite of in situ microanalytical methods. Possible contaminants collected from the cleanrooms of the spacecraft assembly and extraterrestrial sample curation center (ESCuC) were also analyzed in the same manner as category 3 particles for comparison. Our data were integrated with those of the preliminary examination team for category 3 particles. Possible origins for the category 3 particles include contamination before and after the operation of the Hayabusa spacecraft.  相似文献   

Special section on the Cooperative Monitoring Program of Ariake Sea (COMPAS)     

Yuichi Hayami  Shinichiro Yano  Toshiya Katano 《Journal of Oceanography》2018,74(6):549-549

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POC fluxes estimated from 234Th in late spring–early summer in the western subarctic North Pacific     

Hajime Kawakami  Makio C. Honda  Kazuhiko Matsumoto  Masahide Wakita  Minoru Kitamura  Tetsuichi Fujiki  Shuichi Watanabe 《Journal of Oceanography》2015,71(3):311-324

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Geochemical Characteristics of Apatite in Heavy REE‐rich Deep‐Sea Mud from Minami‐Torishima Area,Southeastern Japan     

Yoshiaki Kon  Mihoko Hoshino  Kenzo Sanematsu  Sayaka Morita  Maiko Tsunematsu  Nobuyuki Okamoto  Nobuhiko Yano  Mikiya Tanaka  Tetsuichi Takagi 《Resource Geology》2014,64(1):47-57

We have conducted geochemical and mineralogical investigations of the rare earth and yttrium (REY)‐rich mud from the Minami‐Torishima area in the Pacific in order to clarify the concentration of REY and their host‐phase in the mud. X‐ray diffraction analysis shows that the mud is mainly composed of phillipsite, fluorapatite, quartz, albite, illite and montmorillonite. Whole‐rock CaO, P₂O₅ and total REY contents of the mud are positively correlated. Relative abundance of apatite is also positively correlated to P₂O₅ and total REY contents. These correlations suggest that apatite is the main host of the P₂O₅ and REY in the mud. We make in situ compositional analyses of constituent minerals in the REY mud. The results show that the apatite is abundant in REY (9300–32,000 ppm) and is characterized by a negative Ce anomaly and enrichment in heavy rare‐earth elements. This abundance and composition of REY of the mud is similar those of fish debris apatites. In contrast, phillipsite is less abundant in REY (60–170 ppm). Therefore we conclude that the main REY host phase of the mud is apatite.  相似文献   

Evaluation of various satellite sensors for waterline extraction in a coral reef environment: Majuro Atoll, Marshall Islands   总被引：4，自引：0，他引：4  

Hiroya Yamano  Hiroto Shimazaki  Tsuneo Matsunaga  Albon Ishoda  Caleb McClennen  Hiromune Yokoki  Kazuhiko Fujita  Yoko Osawa  Hajime Kayanne 《Geomorphology》2006,82(3-4):398-411

The ability of five satellite sensor bands (IKONOS band 4, Terra ASTER bands 3 and 4, and Landsat ETM+ bands 4 and 5) was examined to extract the waterline at coral reef coasts (Majuro Atoll, Marshall Islands) using different wavelength regions (near infrared [NIR] and shortwave infrared [SWIR]) and different spatial resolutions (4, 15, and 30 m). After performing georeferencing and normalization of the images, density slicing was used to extract the waterline. Comparisons of extracted waterline positions with ground-level data for eight transects and global positioning system (GPS) tracks of the island shorelines showed that NIR bands were superior to SWIR bands because of the characteristics of the coral reef coasts, including a lack of foam and suspended sediments (which can affect the NIR wavelength region, if present) and the presence of remnant water on reef flats during low tide (which can affect the SWIR wavelength region). A linear relationship was found between the estimation errors of waterline positions and the spatial resolutions of the NIR sensors. Analysis on estimation errors and image costs showed that Terra ASTER band 3 was the most cost-effective sensor for extracting waterlines with reasonable accuracy. The results serve as general guidelines for using satellite-derived data to estimate intertidal topography and detect and monitor shorelines in coral reef environments.  相似文献   

A Three-Dimensional Simulation of HO x Concentrations Over East Asia During TRACE-P     

Meigen Zhang  Hajime Akimoto  Itsushi Uno 《Journal of Atmospheric Chemistry》2006,54(3):233-254

The Models-3 Community Multi-scale Air Quality modeling system (CMAQ) coupled with the Regional Atmospheric Modeling System (RAMS) is used to simulate three-dimensional concentration distributions of hydroxyl (OH) and hydroperoxyl (HO₂) radicals over the western Pacific Ocean during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) field campaign. Modeled values of OH and HO₂ and their closely related chemical species and photolysis rates are compared with observational data collected onboard the DC-8 aircraft. Comparison shows that the model reasonably reproduced these observed values over a broad range of conditions with an overall tendency to overestimate the measured OH and HO₂ by a factor of 1.56 and 1.24, respectively. A case study of OH, HO₂ and their closely related chemical species and photolysis rates along the DC-8 flights 11 and 12 conducted on 17–18 March 2001 shows that the model reproduces the temporal and spatial variations reasonable well, and produces more reliable OH and HO₂ concentrations in the polluted environment than in the clean marine boundary layer.  相似文献   

Oxygen isotopic and chemical compositions of cosmic spherules collected from the Antarctic ice sheet: Implications for their precursor materials     

Toru Yada  Tomoki Nakamura  Noriko Matsumoto  Hajime Hiyagon  Naoji Sugiura  Nobuo Takaoka 《Geochimica et cosmochimica acta》2005,69(24):5789-5804

Bulk chemical compositions and oxygen isotopic compositions were analyzed for 48 stony cosmic spherules (melted micrometeorites) collected from the Antarctic ice sheet using electron- and ion-microprobes. No clear correlation was found between their isotopic compositions and textures. The oxygen isotopic compositions showed an extremely wide range from −28‰ to +93‰ in δ¹⁸O and from −21‰ to +13‰ in Δ¹⁷O. In δ¹⁸O-δ¹⁷O space, most samples (38 out of 48) plot close to the terrestrial fractionation line, but 7 samples plot along the carbonaceous chondrite anhydrous mineral (CCAM) line. Three samples plot well above the terrestrial fractionation line. One of these has a Δ¹⁷O of +13‰, the largest value ever found in solar system materials. One possible precursor for this spherule could be ¹⁶O-poor planetary material that is still unknown as a meteorite. The majority of the remaining spherules are thought to be related to carbonaceous chondrites.  相似文献