We performed a survey from 27 to 30 October 2005 in the seagrass meadows along the southeast coast of Talibong Island. Trang province. Thailand. We found three typical characteristics of dugong grazing scars on Enhalus acoroides leaves. The blades were unevenly cut (not in straight lines), and these same general shapes were observed at the same abovegroiind height on all leaves. Tooth marks consistent with dugong molars were observed on E. acoroides leaves, and the shapes of grazing scars in E. acoroides meadows were elliptical, whereas scars found in meadows of small seagrass species were meandering lines.

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Seasonal variation of ecological components (epiphytes and aquatic animals) in the seagrass beds (Zostera marina L.) in brackish Lake Obuchi. located in the center of the Shimokita Peninsula in Aomori Prefecture, was observed from June 2004 to April 2005. The biomass of Z. marina varied from maximum in June to the minimum in April. The most numerous species among the epiphytes on the leaf of Z. marina were Cocconeis placentula and Licmophora flabellata belonged to the Bacillariophyceae. The dominant taxa of the aquatic animals in the seagrass beds were the Arthropoda (Ampithoe valida. Gnorimosphaeroma rayi, and Melita sp.). Mollusca (Musculista senhousia) and Annelida (Polydora sp.). From the relationships among water temperature, salinity and the density of epiphytes. Arthropoda and Annelida in the seagrass beds, it was clarified that the densities of them strongly depend on water temperature. The division ratios of organic carbon among the ecological components in the seagrass beds. Z marina, epiphytes. Arthropoda. Mollusca and Annelida, were 100 : 7 : 10:5: 0.02 in summer, and 100 : 11 : 0.1 : 0.4 : 0.0003 in winter, respectively.

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Artificial nightlight emitted from buildings and road lightsin the city area were extracted by using a noise reduction filter (NRF) from Defense Meteorological Satellite Program/Optical Linescan System (DMSP/OLS) nighttime imagery which observed during the year 1999. The NRF finds harmonic signal component and its bias from each pixel of the time series imagery and other random signals are eliminated as the noises. We applied this NRF to the DMSP /OLS time series datasct. If pixels contained stable values through the time series dataset. then those stable values are extracted as the bias components. And those are defined as artificial nighttime lights. However, the levels of extracted those artificial lights were shifted by the season and its latitude. To clarify the shift of the level, we applied spectral analysis by the Fast Fourier Transformation (FFT) to 120 mosaic images which were generated from daily DMSP/OLS data of the year 1999. The result of the FFT analysis showed that the shift of the level was a 1-year cycle component that was affected by sunlight. Then, we developed an improving method of the artificial nightlight extraction by removing 1-year cycle component from the artificial light. And we made a comparison of the difference between the artificial lights extracted by NRF and our method by using four selected pixels at different latitude in the study area, and it was confirmed that the level of the bias were corrected by our method.

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Although the improvement of data loggers has revealed the ecology of a variety of marine creatures, the ecology of deep sea fish has been poorly documented, principally as a result of difficulties in tagging these fish species with data loggers. A new method of tagging fish with data loggers using the Data Logger System (DLS)was developed for in situ underwater tagging of deep sea fish. The method is designed to tag fish with data loggers through bait fishing, such as long line fishing, to install an external towed data logger onto the fish. After a certain time, the data logger is automatically released from the fish and floats to surface of the sea to be recovered. Therefore, the data logger can be recovered without capturing the fish. The prototype was tested with some pacific cods (Gadus macmcephalusYm indoor water tanks of the Toyama Prefectural Fisheries Research Institute. The DLS successfully attached the data loggers to the cods. The acceleration data obtained by the DLS was compared with data from a directly attached logger. The acceleration data gathered through the DLS suggested to be used for grasping fish movements, which was comparable to the data gathered through the conventional, directly attached data logger.

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A large volume in situ filtration and concentration system (LV-FiCS) was developed to measure the activity concentrations of radionuclides in dissolved and particulate forms in seawater. It consists of a filtration and concentration module (FC module), an electromechanical cable (EM cable), and a pump control unit. The main FC unit enables collection of large (＞70 μm) and small particles (1-70 μm). At the same time, dissolved radionuclides are concentrated onto adsorbents just downstream of the filtration unit. Several kinds of adsorbents are used depending on the radionuclides to be collected. Eight FC modules can be simultaneously attached to the EM cable to collect samples from the surface to depths of either 350 m or 2000 m. depending on the cable used. The LV-FiCS was operated during several cruises in Japanese coastal waters and in the Pacific Ocean. The FC module successfully filtered 4-11 m^3 of seawater over 3-5 h. Vertical profiles of the size-fractionated particulate and dissolved forms of radionuclides such as 231Th， 239．240Pu，32．33P， 7Be，99Tc， and 137Cs were obtained.

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The sinking flux of particulate organic matter to the sediment is important process to analyse the formation mechanism of oxygen deplete water mass. In this study, we carried out the simulation for sensitivity analysis of two countermeasure plans on the sinking flux of particulate organic matter using numerical ecosystem model in Mikawa Bay. One is the case of the reduced loading from river by 50 % for organic substance and nutrients, and the other is the case that the clam resources would increase to the level in 1960. The results showed that the clam restoration is more effective than the reduced loading from rivers to lower the sinking flux of particulate organic matter. The results showed that the variation of COD concentration at open boundary of the Mikawa Bay also affect on the sinking flux of particulate organic matter. Therefore the case that DOC degradation rate parameter change 0.005 (labile) to 0.0005 (refractory) showed the sinking flux of particulate organic matter decreased. Even if DOC concentration becomes high at the boundary, its effect on the sinking flux is small.

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Scientific research in the deep ocean is a recent branch of wide-ranging marine research. The requirements of deep ocean scientific research have led to increasingly larger areas to be investigated while the mesh of investigations has become finer and finer, and deeper and deeper. In the deep seas the scientist ventures into an unlimited treasure house of knowledge: it is truly a voyage into the unknown. It has been almost twenty years since ”Shinkai6500” was launched in 1989. and the vehicle providing the world's greatest depth capability for a manned submersible, and also the vehicle has been providing for scientists a means to enable safely access and directly observe the deep ocean at a time when it was difficult for a man to venture to the deep seafloor. However, the time has come to consider a future deep submergence research vehicle as a succeeding vehicle for ”Shinkai6500”. This paper covers the result of study on the conceptual designs of two types of manned deep submergence research vehicles: 11000m submergence vehicle (full depth) and 6500m submergence vehicle (two spheres). On the other hand, during this same time period of twenty years, remotely operated vehicles and autonomous unmanned vehicles were developed worldwide and became available with advanced controlling and sensing technologies. Today, a lot of investigations and operations in the deep sea are utilizing these unmanned systems. Nevertheless, it is still very important that humans work in situ to directly observe and act. This man's capability generating innovative knowledge and hypotheses will be necessary at any time and in any period. Even if unmanned technologies are advanced in the field of natural science, the necessity of field work with man's presence will not be diminished. Consequently, future capable manned submergence vehicles that are responsive to the needs of scientific research in the deep ocean must be used in collaboration with various kinds of unmanned vehicles. This study was carried out by the ”ad hoc Committee” organized in the Japan Deep Sea Technology Association with additional current status regarding ”Shinkai6500”.

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