海洋理工学会誌
Online ISSN : 2188-3262
Print ISSN : 1341-2752
ISSN-L : 1341-2752
11 巻 , 1 号
選択された号の論文の12件中1~12を表示しています
原著
  • 石井 憲, 澤田 浩一
    2005 年 11 巻 1 号 p. 1-6
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    Target strength (TS) of squid is required to convert acoustic integration values to estimates of the existing biomass of squid. Squid are weak in both body and acoustic reflection compared to fish. We constructed a new TS measurement system for squid considering the above characteristics. Contrary to the usual TS measurement system for fish, a target is fixed and a transducer then rotates around the target in this system. A personal computer (PC) has been installed for automatic measurements including synchronization between rotation and acoustic data acquisition. A control program that consists of six sub-programs integrated via network has been developed for the TS measurement systems. The main concepts of the control program are 1) adaptability to other TS measurement system. 2) flexibility. 3) and a user-friendly man-machine interface. Any combinations within six sub-programs can be separately installed on different PCs connected to the same network or on the same PC. The six sub-programs work as one control program. The required functions of the TS measurement mechanism are classified into three command groups : 'Basic' commands used commonly in rotating systems, 'Network' commands related to the priority among PCs and 'Proprietary' commands on each mechanism. The network-integrated program has determined the precise positioning of a transducer and the easy synchronization with the echo data acquisition system. It also monitors the angle and the current status information of the rotating mechanism from several PCs connected to the network as monitors in addition to the control PC as a controller.
  • 角田 晋也, 佐々木 保徳, 中田 喜三郎
    2005 年 11 巻 1 号 p. 7-11
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    The scientific mission of the project ARGO is to build a real-time, high-resolution monitoring system for upper and middle layers of the world ocean, which consists of Argo floats, satellite-communication systems, and information-processing technologies. The ocean monitoring system will obtain the high quality data of upper and middle layers of the world ocean almost simultaneously with very high space-time resolution. That will help us to understand large scale, on going oceanic variations. An easy-touse method of determining launching points to deploy floats drifting with certain average spacing is proposed. Counting the number of floats drifting within a certain radius from the last launching point, this method determines the next launching point successively. It is easy to adopt this method even on cruise tracks curved or broken.
  • 西村 清和, 上嶋 正人, 徳岡 隆夫, 吹田 歩, 竹内 倶佳
    2005 年 11 巻 1 号 p. 13-19
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    When geological surveys or environmental studies are carried out in brackish water lakes like Lake Nakaumi and Lake Shinji out. a sub-bottom profiler (SBP) which images the geological structure of the lake sediment and sidescan sonar (SSS) which reveals the microtopography of the lake bottom are essential survey equipment. However, conventional survey equipment was designed for marine operations, and as a result, it is big and difficult to use in lakes. A system was developed to introduce low-cost and compact sidescan sonar and sub-bottom profiler which can be deployed from a small boat and easily used in the survey of the brackish water. The trade name of the digital sidescan sonar is SportScan (Imagenex Technology Corp.. Canada) and the trade name of the sub-bottom profiler is StrataBox (SyQwest Inc.. USA). In this paper, it focuses on the sidescan sonar. The low-cost sidescan sonar is composed of towfish and towing cable, and is connected to power (10-16VDC) and notebook PC directly with the shipboard towing cable. The operating frequency of the sidescan sonar is 330 kHz. available operating range is 15 m-120 m, and the best towing speed is 2-3 knots. Surveys of Lake Nakaumi and Miho Bay were carried out by combining sidescan sonar /sub-bottom profiler and a DGPS receiver, and navigation used map software ”KASHMIR 3D”. The sidescan sonar survey has produced a mosaic map of the sediment surface.
  • 安岡 澄人, 畑 恭子, 芳川 忍, 中野 拓治, 白谷 栄作, 中田 喜三郎
    2005 年 11 巻 1 号 p. 21-33
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    A pelagic-benthic coupled ecosystem model has been developed for a tidal mud flat and shallow-water area of Ariake Bay, reflecting key features of the area. e.g.. development of anoxic conditions in the sediment, composition of the benthic biomass, deposition and resuspension of sediments, and their influences on the nitrogen cycle. The nitrogen cycle and budget were estimated through simulation run for a year. Water purification capability, defined by the removal of nitrogen from the system, was estimated at 7.2 mgN m”2 day”1. Denitrification corresponds to 97% of the total removal flux of nitrogen from the system. High primary production rates exceeding the total transformation rate from organic nitrogen to inorganic nitrogen shows that this mud flat and shallow-water system is an autotrophic system. Except for artificially intervened bivalves grounds, bivalves in the muddy flat and shallow-water area haveonly a limited role concerning the control over the blooming of phytoplankton.
  • 山本 譲司, 中田 喜三郎, 堀口 文男
    2005 年 11 巻 1 号 p. 35-44
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    It has been difficult to accurately estimate TBT concentrations in sediments using conventional models, in which TBT concentrations in sediments were calculated only by taking temperature and dissolved oxygen levels into account. In this study, a new model has been developed, and processes, in which sediments undertake re-suspension associated with the flow of the overlying water, are incorporated into the model to reproduce more realistic phenomena in marine environments. The calculated results of TBT concentrations in water and sediments were compared with field data. As the result, the model was validated with a good agreement between them. In addition, the persistence of TBT in sediments much longer than that in water was revealed in the TBT fate simulated by the model, indicating adverse impacts of TBT on benthic organisms.
  • 山本 譲司, 堀口 文男, 中田 喜三郎, 中西 準子
    2005 年 11 巻 1 号 p. 45-51
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    This study involved the development of a Windows-compatible model that is a simple exposure forecasting system that predicts environmental concentrations of specific chemicals in specific marine areas. The model was used to evaluate the exposure of marine organisms to an antifoulant chemical in Tokyo Bay. These results were then used in a risk assessment study. In addition, using existing data, a calculation (distribution of current, temperature, salinity, plankton and detritus concentration) for Tokyo Bay, over four seasons, was carried out using a three-dimensional flow model and an ecosystem model. The calculation results for each season was stored in a database, and then combined with a chemical fate-prediction model for marine areas. This model can be adapted for operation in Windows® with a Graphic User Interface (GUI) so that it is easy to use by other operators. With a simple system to input parameters, this prototype modeling system enabled detailed prediction of environmental concentrations of TBT in Tokyo Bay and was used in a risk assessment for several species of marine organisms exposed to those TBT concentrations.
  • 中西 喜栄, 細谷 誠一, 中西 佳子, 荒井 修亮, カンジャナ アドゥンヤヌコソン
    2005 年 11 巻 1 号 p. 53-57
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    Survey on distribution of seagrass beds and dugong trenches was performed from February 27 to March 2. 2001 around Libong Island. Trang Province. Thailand. Seagrass beds were observed at southeast to north coast of Libong Island and between Libong Island and the Malay Peninsula. Ten species of seagrasses were identified there. Among the ten species. Halophila ovalis, Cymodocea serrulata and Cymodocea rotundata dominated. The total number of 22 dugongs were observed on February 27 and 28 on and around these seagrass beds by aerial surveys. Dugong trenches were distributed densely in the communities where Halopkila ovalisdominated orHalophilaovalis and Cymodocea serrulata occured together. Therefore, we concluded that dugongs in this study site fed selectively at the Halophila oralis community. We observed the feeding trenches at the nine species of them, but we did not observe the obvious feeding traces of dugongs at Enhalusacoroides. We did not observe the selectivity that dugong prefer to feed at the seagrass bed with less sediment on leaves.
速報
  • 安岡 澄人, 石川 知樹, 中野 拓治, 白谷 栄作, 中田 喜三郎
    2005 年 11 巻 1 号 p. 59-66
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    A comprehensive field study concerning a mud tidal flat and shallow-water area in Ariake Bay demonstrated distinct nature of nitrogen cycle in the mud flat system. Fine particles, low percolation and anoxic environments in sediments determined the relative abundance of inorganic nitrogen compounds in sediments. Ammonium was highly accumulated in interstitial water of sediments. Denitrification appeared to be limited by low nitrification in thin oxidized layer of sediments, together with the limited supply of nitrate from the overlying water. The composition of benthic biomass in terms of nitrogen were characterized by abundant bacteria and less abundant macro-benthos in comparison with those reported in sandy tidal flats. Bivalves were however observed to be dense in artificially intervened area, such as bivalve grounds and oyster beds.
  • 正木 宏和, 中田 喜三郎
    2005 年 11 巻 1 号 p. 67-70
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    We estimated the amount of silicate loading to the Lakes Shinji and Nakaumi from April 1999 to March 2000. The IIil River is the major source of nitrogen and phosphorus to the Lakes Shinji and Nakaumi. A L-Q relationship based on the observations is used to estimate the amount of loading such as nitrogen and phosphorus. The computed results for nitrogen and phosphorus concentration distribution show good agreement with observations. In terms of silicate, there was no observations. To estimate the amount of silicate loading, the inverse problem method is applied. As a results, the estimated the amount of silicate loading is 21 (ton/day) to the Lake Shinji and 3 (ton/day) in the Lake Nakaumi. The IHi River accounts for 75% of the whole loading.
  • 酒井 亨, 中田 喜三郎
    2005 年 11 巻 1 号 p. 71-76
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    In order to investigate the possibility of seasonal succession between a grazing food web and a micro-bial food web. and seasonal variation of the dominant species of phytoplankton. a lower-trophic marine ecosystem model has been developed. The preypredator interactions and the interspecies competition were incorporated into this model. This improved model was applied to Ise Bay for 1995 by coupling with a 3-D hydrodynamic model. In a physical model, the turbulent heat transfer process between sea surface and atmosphere was modified to more realistic formulation, which resulted in better agreement with the observed data. The simulated results of biological processes using a lower-trophic marine ecosystem model showed that a simulated chlorophyll-a variation was reproduced well, and that the dominant plankton species is diatoms through the simulated year. Simulated ANF and bacteria biomasses were compared favorably with the field measurements. But in terms of HNF and picophytoplankton. the simulated results showed some discrepancies.
  • 堤 千華, 市川 光太郎, 赤松 友成, 荒井 修亮, 新家 富雄, 原 武史, カンジャナ アドゥンヤヌコソン
    2005 年 11 巻 1 号 p. 77-80
    発行日: 2005年
    公開日: 2019/02/16
    ジャーナル フリー
    Dugongs {Dugong dugon) are herbivorous marine mammals and endangered species. Unfortunately, the lack of basic research especially on use of seagrass patches by dugongs prevents us from taking any effective countermeasures for the conservation. In this study, to monitor feeding behavior of dugongs in the seagrass bed of a tidal flat, we propose a visual-acoustic combined observation method which is comprised of the visual observation and the acoustic observation using a digital camera and automatic underwater sound monitoring systems for dugong (AUSOMS-D). This new observation method was tested in Thai waters. The increase in the number of dugong feeding trails was observed during nighttime by the visual observation. Dugong calls and feeding sounds were recorded by the acoustic observation. The increase of the dugong feeding trails coincided with the feeding sounds. Therefore, the visual-acoustic combined observation method is effective in monitoring feeding behavior of dugongs. This method has technical benefits not to impact both on the dugongs and the seagrass beds.
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