Three-dimensional mapping of red stingray (Dasyatis akajei) movement with reference to bottom topography     

Otaki  Takayoshi  Hamana  Masahiro  Tanoe  Hideaki  Miyazaki  Nobuyuki  Shibuno  Takuro  Komatsu  Teruhisa 《Ocean Science Journal》2015,50(2):327-334

Most demersal fishes maintain strong relations with bottom substrates and bottom depths and/or topography during their lives. It is important to know these relations to for understand their lives. In Tokyo Bay, red stingray, Dasyatis akajei, classified as near-threatened species by IUCN, has increased since the 1980s. It is a top predator and engages in ecosystem engineer by mixing the sand bed surface through burring behavior, and greatly influences a coastal ecosystem. It is reported that this species invades in plage and tidal flats and has sometimes injured beachgoers and people gathering clams in Tokyo bay. Thus, it is necessary to know its behavior and habitat use to avoid accidents and to better conserve the biodiversity of ecosystems. However, previous studies have not examined its relationship with the bottom environment. This study aims to describe its behavior in relation to the bottom environment. We sounded three dimensional bottom topography of their habitat off Kaneda Cove in Tokyo Bay with interferometric sidescan sonar system and traced the movement of red stingrays by attaching a data logger system to survey their migration. The results revealed that red stingray repeated vertical movement between the surface and bottom, and used not only sand beds but also rocky beds.

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A three-dimensional numerical model of hydrodynamics and water quality in Hakata Bay   总被引：1，自引：0，他引：1  

Yongming Shen  Yonghong Zheng  Toshimitsu Komatsu  Naoko Kohashi 《Ocean Engineering》2002,29(4):461-473

The hydrodynamics and water quality in Hakata Bay, Japan, are strongly affected by the seasonal variations in both the gravitational circulation and the stratification in the bay. The three-dimensional hydrodynamics and water quality model has been developed to simulate the long-term transport and fate of pollutants in the system. The model is unique in that it completely integrates the refined modelling of the hydrodynamics, biochemical reactions and the ecosystem in the coastal areas. It is a 3-dimensional segmented model which is capable of resolving mean daily variations in all the parameters relevant to pollution control. It predicts daily fluctuations in the oxygen content at different depths in water throughout the year. It takes into account transport and settling of pollutant particles. It predicts light penetration from computed turbidity variations. It includes interactions between the ecosystem and water quality, through nutrient cycling and photosynthesis. The model has been calibrated well against the data set of historical water quality observations in Hakata Bay.  相似文献   

Temporal fluctuations of water temperature in aSargassum forest     

Teruhisa Komatsu 《Journal of Oceanography》1985,41(4):235-243

This paper examines the influence of aSargassum forest on temporal fluctuations in temperatures of surrounding water in relation to the thermal structure of water in and above theSargassum forest. Water temperature records were obtained at about one-minute intervals for almost two days in May 1977 during the season of luxuriant seaweed growth, and in August 1977 during the season of little growth. The fluctuations were divided into two types. (1) A diurnal fluctuation under the forest with about a three hour lag behind that above the forest during the season of luxuriant growth but with about a 30 min lag during the season of little growth. (2) Sharp spike-like fluctuations with periods shorter than five minutes appearing only in the dense canopy or floating seaweeds in the surface and subsurface layers during the period of luxuriant growth. The luxuriant forest ofSargassum seems to influence the spatial distribution of water temperature and consequently seems to induce the fluctuations mentioned above. The relationship between short period fluctuations and behaviours of larval fishes are discussed.  相似文献   

Origin of glacial–fluvial landforms in the Azas Plateau volcanic field, the Tuva Republic, Russia: Role of ice–magma interaction     

Goro Komatsu  Sergei G. Arzhannikov  Anastasia V. Arzhannikova  Gian Gabriele Ori 《Geomorphology》2007,88(3-4):352-366

The basaltic Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federation. The area was glaciated multiple times, and the field is characterized by the formation of subglacial volcanoes called tuyas, but subaerial volcanoes and lava fields also exist. A combined study of remote sensing and field observations in the vicinity of the tuyas in the southeastern Azas Plateau volcanic field identified landforms that are best explained by the jökulhlaup hypothesis. The landforms include elongated hills, paleochannels, and butte and basin topography. These landforms are hypothesized to have formed by both erosion and deposition caused by high-energy water streams. The triggering for the hypothesized jökulhlaups was either melting of ice by subglacial volcanism and/or destabilization of ice-dammed/subglacial reservoirs. The age estimation of the flood events is difficult, but they probably occurred during the ice ages of the Quaternary, as late as in the Middle-Late Pleistocene.  相似文献   

Geochemical Features of Vein Anhydrite from the Kakkonda Geothermal System, Northeast Japan     

Munetake Sasaki    Koichiro Fujimoto    Hitoshi Tsukamoto    Takayuki Sawaki    Masakatsu Sasada    Masanori Kurosawa  Masahiko Yagi    Yoichi Muramatsu    Osamu Kato  +  Ryo Komatsu  +  Kaichiro Kasai  + Nobuo Doi+ 《Resource Geology》2003,53(2):127-142

Abstract. Cathodoluminescence (CL) color, rare earth element (REE) content, sulfur and oxygen isotopes and fluid inclusions of anhydrite, which frequently filled in hydrothermal veins in the Kakkonda geothermal system, were investigated to elucidate the spatial, temporal and genetical evolution of fluids in the deep reservoir. The anhydrite samples studied are classified into four types based on CL colors and REE contents: type-N (no color), type-G (green color), type-T (tan color) and type-S (tan color with a high REE content). In the shallow reservoir, only type-N anhydrite is observed. In the deep reservoir, type-G anhydrite occurs in vertical veins whereas type-T and -N in lateral veins. Type-S anhydrite occurs in the heat-source Kakkonda Granite. The CL textures revealed that type-G anhydrite deposited earlier than type-T in the deep reservoir, implying that fracture system was changed from predominantly vertical to lateral.
Studies of fluid inclusions and δ³⁴S and δ¹⁸O values of the samples indicate that type-N anhydrite deposited from diluted fluids derived from meteoric water, whereas type-G, -T and -S anhydrites deposited from magmatic brines derived from the Kakkonda Granite with the exception of some of type-G with recrystallization texture and no primary fluid inclusion, which deposited from fossil seawater preserved in the sedimentary rocks. Type-G, -T and -S anhydrites exhibit remarkably different chondrite-normalized REE patterns with a positive Eu anomaly, with a convex shape (peak at Sm or Eu) and with a negative Eu anomaly, respectively. The difference in the patterns might result from the different extent of hydrothermal alteration of the reservoir rocks and contribution of the magmatic fluids.  相似文献   

Benthic Foraminifera in Siliceous Black Ore from the Ezuri Kuroko Deposit, Hokuroku District, Japan     

Kosei KOMURO  Naoaki AOKI  Yoshimichi KAJIWARA 《Resource Geology》2002,52(2):111-121

Abstract: Abundant benthic foraminifera have been identified in thin sections of the siliceous black ore in the Ezuri Kuroko deposit, Hokuroku, Japan. By treating samples with conventional hydrofluoric acid digestion techniques, sponge spicules and radiolaria have also been recognized in the residue. Under microscopic observations, 94 individual foraminiferal specimens have been detected. However, as it is difficult to identify species or genera by means of microscope observations alone, only a small number of genera have been identified based on morphology. The foraminiferal assemblage is composed predominantly of agglutinated species (83%) with subordinate calcareous species (17%), and is assigned to the Cyclammina Assemblage based on the preponderance of Cyclammina (57%). The foraminifera are generally well preserved within micro‐crystalline to cryptocrystalline quartz, and exhibit no obvious features related to compaction or secondary deformation. Textural observations suggest that the siliceous component of this rock was not derived from an allochthonous block but instead constitutes autochthonous proto‐Kuroko sediment. The Cyclammina Assemblage in the ore is different from recently described foraminiferal assemblages in the vicinity of present deep‐sea hydrothermal vents, but is identical to those found in black shales of the Onnagawa to Funakawa stages in the Green Tuff region. The proto‐Kuroko sediment is assumed to have been deposited in an oxygen‐deficient environment within a closed, deep‐seated basin. The existence of siliceous microfossils suggests that the silica in the siliceous ore did not originate from silica sinter deposits produced by submarine hydrothermal activities, but from a biogenic siliceous ooze, probably composed of diatoms. Sulfide mineralization in the interstices of some of the microfossils is inferred to relate primarily to bacterial sulfate reduction associated with the decomposition of organic matter. The later sulfide mineralization associated with larger crystals (which contain fluid inclusions with homogenization temperatures of approximately 250C) cuts across the siliceous masses and foraminiferal septa, and may have been formed after consolidation of the siliceous ooze, accompanying the formation of acidic intrusive rocks during the late Onnagawa stage.  相似文献   

Evaluation of a curve-fitting method for diffuse reflectance spectra in the UV–Visible–NIR wavelength region     

M. Miyamoto  T. Arai  M. Komatsu  A. Yamamoto  T. Mikouchi 《Polar Science》2009,3(2):110-116

The Modified Gaussian Method (MGM) proposed by Sunshine et al. [Sunshine, J.M., Pieters, C.M., Pratt, S.F., 1990. Deconvolution of mineral absorption bands: an improved approach. Journal of Geophysical Research 95, 6955–6966.] is generally used to decompose spectra in the UV–Visible–NIR wavelength region into the characteristic absorption bands of minerals. Here, we compare the optimized results obtained using different curve-fitting methods for this spectrum. The result obtained using the Gaussian function for the absorption band shows a better fit than that obtained using the Lorentzian function. The background continuum of a quadratic polynomial for the wavenumber provides a better result than does the linear function for the wavenumber. We successfully decomposed the spectra of ordinary chondrites and eucrites into the absorption bands of olivine and pyroxene. The wavelength positions of these absorption bands are broadly consistent with the Fe contents of olivine and pyroxene. Although the present results are derived from a limited number of spectra, they are of use in terms of the decomposition of diffuse reflectance spectra.  相似文献   

Comparison of carbon cycle between the western Pacific subarctic and subtropical time-series stations: highlights of the K2S1 project     

Makio C. Honda  Masahide Wakita  Kazuhiko Matsumoto  Tetsuichi Fujiki  Eko Siswanto  Kosei Sasaoka  Hajime Kawakami  Yoshihisa Mino  Chiho Sukigara  Minoru Kitamura  Yoshikazu Sasai  Sherwood L. Smith  Taketo Hashioka  Chisato Yoshikawa  Katsunori Kimoto  Shuichi Watanabe  Toru Kobari  Toshi Nagata  Koji Hamasaki  Ryo Kaneko  Mario Uchimiya  Hideki Fukuda  Osamu Abe  Toshiro Saino 《Journal of Oceanography》2017,73(5):647-667

A comparative study of ecosystems and biogeochemistry at time-series stations in the subarctic gyre (K2) and subtropical region (S1) of the western North Pacific Ocean (K2S1 project) was conducted between 2010 and 2013 to collect essential data about the ecosystem and biological pump in each area and to provide a baseline of information for predicting changes in biologically mediated material cycles in the future. From seasonal chemical and biological observations, general oceanographic settings were verified and annual carbon budgets at both stations were determined. Annual mean of phytoplankton biomass and primary productivity at the oligotrophic station S1 were comparable to that at the eutrophic station K2. Based on chemical/physical observations and numerical simulations, the likely “missing nutrient source” was suggested to include regeneration, meso-scale eddy driven upwelling, meteorological events, and eolian inputs in addition to winter vertical mixing. Time-series observation of carbonate chemistry revealed that ocean acidification (OA) was ongoing at both stations, and that the rate of OA was faster at S1 than at K2 although OA at K2 is more critical for calcifying organisms.  相似文献   

Impacts of the Nakhodka heavy-oil spill on an intertidal ecosystem: an approach to impact evaluation using geographical information system     

Teruhisa K  Masahiro N  Hiroshi K  Tomoko Y  Kouichi O;Marine Life Research Group of Takeno 《Marine pollution bulletin》2003,47(1-6):99-104

A major heavy-oil spill from the Russian tanker Nakhodka occurred in the Sea of Japan on 2 January 1997. We investigated the impacts of this spill on a rocky intertidal ecosystem along the southern coast of the Sea of Japan. We selected Imago-Ura Cove as our study site to observe temporal changes along the oiled shore, because minimal cleaning effort was made in this area. Field surveys were conducted every autumn and spring from 1997 to 2000. We measured coverage by macroalgae in 1 x 1-m(2) quadrats and counted the animals in 5 x 5-m(2) quadrats along the intertidal zone. Changes in the ecosystem caused by the oil spill were analyzed by applying a geographical information system (GIS) to the Sea of Japan for the first time. The GIS showed that following the accident there were heavily oiled areas in sheltered regions, but these decreased over the three years. It also showed that coverage by macroalgae and the number of animals increased, although some species of algae with microscopic sporophyte generations, and some populations of perennial shellfish, remained stable or decreased during the study period. GIS was able to trace temporal changes in intertidal communities resulting from the impacts of heavy oil on flora and fauna at a spatial scale of 10-100 m. GIS is thus a practical tool for visualizing, analyzing, and monitoring changes in an ecosystem polluted by oil, taking into account topographic differences along the coastline.  相似文献   

Multivariate analysis of trace elements in shallow groundwater in Fuchu in western Tokyo Metropolis,Japan     

Dang Quoc Thuyet  Hirotaka Saito  Takeshi Saito  Shigeoki Moritani  Yuji Kohgo  Toshiko Komatsu 《Environmental Earth Sciences》2016,75(7):559

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