An artificial seamound is a structure which induces vertical mixing of seawater and prompts primary production, but its quantitave evaluation method has not been established. In this study, we developed an image analysis method for density measurement by using dye and transmitted light. Vertical mixing induced by a moving mound in stratified still water was evaluated in a water tank. We found that vertical mixing is large in cases that density interface of two-layer flow is broken, and density can change by mixing at pycnocline even if density difference is small. Also we compared the resuls of laboratory experiments with three-dimensional LES numerical simulation. It was found that the numerical simulation can reproduce results of laboratory experiments, and it is expected that the model can evaluate mixing effects under more complicated conditions comforming to real sea states.

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 In order to investigate seawater exchange processes in Shirahama Bay and Funauki Bay, Okinawa, Japan, which are mutually connected by a channel at the inner parts of the bays, observational, numerical, and theoretical studies are conducted in this study. In-situ observations and numerical simulations indicate that periodic currents in the connecting channel are dominate in response to flood tidal and ebb tide, and the stagnation of river-origin and low-salinity water is often observed at the 10-cm surface layer in Funauki Bay. Continuum theory of momentum and mass transfer suggest that periodic currents and steady-state flows among the bays and ocean depend mainly on the differences of depth and length among the two bays. As a result of the geographical features, it is concluded that river-origin water likely stagnates in Funauki Bay over the long periods of time, compared to Shirahama Bay.

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 A novel numerical method is proposed with the aim of simulation of heat diffusion problems associated with coastal engineering. The method is founded on the solution of continuity, Navier-Stokes and heat diffusion equations in closure with Sub-Particle Scale turbulence model (according to Large Eddy Simulation approach) within a SPH (Smoothed Particle Hydrodynamics) framework. Boussinesq approximation is applied in order to take the effects of buoyancy into consideration. The model is first verified by considering a set of benchmark tests, and then applied into the simulation of a simplified problem of heated effluent into coastal waters.

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 We carried out a 3-D numerical simulation of the Ariake Sea for the heavy rainfall event in northern Kyushu in July 2012, and reproduced the large-scale salinity stratification in Isahaya Bay. In order to investigate the wind response of freshwaters from the Chikugo River and the Kikuchi River, the numerical experiments were conducted under three hypothetical wind conditions, i.e., the conditions of windless, 10 m/s northeasterly wind and 10 m/s southwesterly wind. The residence time and the existence rate of river water in Isahaya Bay were quantified, and the representative residence time was estimated by fitting an empirical function to the existence rate. The northeasterly wind enhances the inflow of the Chikugo River water into Isahaya Bay and also promotes the outflow from the bay, so the residence time is found to become shorter than the windless condition. On the other hand, the southwesterly wind reduces the inflow of freshwaters from the Chikugo River, and makes the residence time very short. The inflow of the Kikuchi River water into Isahaya Bay is restricted by the northeasterly wind, and enhanced by the interaction between the southwesterly wind and the tidal motion.

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 While recreational waterfront in urban area has been developed, chronical water quality degradation such as red tide and sewage water inflow has been occurred. Monitoring flow field around estuaries is required for appropriate water management. However, it is technically challenging to measure or calculate river discharge in estuaries due to complexity of its flow structure. This study discusses a method of measuring discharge of two-layered flow field by a stationary H-ADCP at Odaibakaihin park. Firstly, in a preliminary survey by an ADCP, a phase shift was observed in tidal velocity components of upper layer and lower layer in the vertical direction, which can be utilized to detect boundary of two layers and to determine thickness of the upper layer. The H-ADCP was settled upward in an angle of 1.5 degrees. Current profiles across the boundary were monitored, and river discharge of two-layered flow field was simultaneously calculated. In addition, a water quality meter combined with two pumping devices was vertically arrayed to observe water properties of multiple layers. Freshwater discharge could be quantified by relating flow rate and salinity of upper layer. This proposed monitoring method enables to monitor discharge of respective water layers and will expand more observatories effectively along analogous estuaries.

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 The characteristics of upwelling, mixing, and residual process of bottom hypoxic waters were investigated from both the field observation at Rokujo tidal flat in the bay-head of Mikawa Bay and an experiment on two-layer stratification designed to imitate the tidal flat. Conclusions obtained in this paper are as follows; (i) Water mixing at the tidal flat often occurs even at moderate wind speed of 4 - 5 m/s. The distinct profile of water quality was observed and hypoxic water mass was mesured to at the edge of the tidal flat. (ii) The magnitude of the lower layer upwelling into tidal flat area was determined by the interaction between pynocline tilting and vertical mixing at the pynocline. (iii) The mixing rate at the slope and tidal flat area seems to increase as Wedderburn number decrease, despite the same degree of Wedderburn number can correspond to different the rate of mixing.

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 The purpose of this study is to analyze the relationship between high turbidity and sulfur, and transfer of a blue tide after upwelling. We achieved ship observations of a blue tide at 24th August 2015 on the inner part of Tokyo Bay. Upwelling water of the blue tide outflowed to the middle layer for analyzing a composition of the blue tide water. It was considered that a density of upwelling water decreased slightly due to mix with around surface water. The blue tide water drifted on a pycnocline for wind driven current and density current. There was a definite positive correlation between turbidity and sulfur from analysis of water samples. Therefore, high turbidity indicates the particulate sulfur element in a blue tide. It was found from the analysis of automatic water quality measurement systems that an upwelling of high density water was not always to produce extensive blue tide. An occurrence of large-scale blue tide may depend on an accumulation of hydrogen sulfide on a flat bottom area of the bay.

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 The water quality characteristics of Isahaya Bay at the time of an occurrence of a large-scale red tide were investigated by analyzing the quality of water that sampled at the surface in the whole area of the bay where a large-scale red tide occurred. The formative process of the large-scale red tide was also clarified by analyzing the data of water quality measured by the Kyushu Regional Agricultural Administration Office. The values of total nitrogen and total phosphorus were over 1.00mg/l and 0.10mg/l respectively, in the region of the red tide occurrence. Its main component was derived from phytoplankton. The dissolved inorganic nitrogen was consumed until it was exhausted. The phosphate-phosphorus, however, remained in a relatively large value. This indicates that the growth of phytoplankton in Isahaya Bay is limited by the dissolved inorganic nitrogen. It was clarified that the river water flowed into the Ariake Sea transported to Isahaya Bay with the vigorous growth of phytoplankton, as one of formative process of large-scale red tides in Isahaya Bay. The red tide in Isahaya Bay trends to become larger scale in the salinity range from 21 PSU to 28 PSU.

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 Using sequential data including chlorophyll-a (chl-a) and sea water density observed by Japan's Ministry of Agriculture, Forestry and Fisheries, we tried to characterize the ecological properties of Chattonella and diatom red tides occurring in Isahaya Bay during the summer and to find indices for prediction of these red tides cessations. Chattonella red tides grew with repeated diel vertical migrations observed moving beyond halocline levels and settling down at the sea bottom in cessation periods. On the other hand diatom red tides grew in the upper layers before it started to fall at the middle period, then it reached full bloom and ceased growth at the bottom layer. Moreover, it was observed that a dominant index of diatoms' cessation was settling clusters which started at the time when the difference of sea water density between upper and lower layers was rather large, unlike Chattonella red tides which were small. Additionally, the velocities of diel vertical migrations of Chattonella and those of settling clusters of diatoms were estimated numerically.

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 There have been numerous estimates of nutrient supply from rivers to coastal seas, and investigations of the impact of nutrients on primary production in coastal ecosystems using the stable isotope (δ¹⁵N) have been reported. However, few of these studies have considered variations in the concentrations of nutrients (dissolved inorganic nitrogen: DIN; and dissolved inorganic phosphorus: DIP) and δ¹⁵N in nitrate in river water. Over a period of 4.5 years we conducted monthly measurements of nutrients and stable isotope in three Class 1 rivers flowing into the Seto Inland Sea. Changes in the concentrations of total nitrogen and total phosphorus in the river water corresponded to variations in DIN and DIP, respectively. There was an increase in δ¹⁵N in nitrate when the DIN concentration decreased, suggesting the influences of denitrification and the assimilation of DIN by phytoplankton in the rivers. The shapes of the mixing curves between DIN and δ¹⁵N changed substantially as a function of river discharge. The results of this study show that to evaluate the impact of nutrient supply from rivers on primary production in coastal seas, it is necessary to construct mixing curves for each change in river discharge.

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 Water quality sensors in Osaka Bay are mostly located along the shore, making it difficult to observe the distribution of hypoxia in summer. To solve this problem, we developed a real-time water quality prediction system in Osaka Bay based on the Regional Ocean Modeling System (ROMS). With a careful quality control to filter out abnormal values in the observed data and a sensitivity analysis on the data assimilation radius, this system successfully simulated the annual change of water quality and the horizontal distribution of hypoxia in summer. With weather forecasting GPV data, the system generally predicted the change in surface temperature and bottom dissolved oxygen, but did not fully predicted the drastic change of dissolved oxygen in the bottom water.

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 To clarify a mechanism of water environmental degradation by coastal landform change in Osaka Bay, numerical analyses have conducted. The results showed that the landfill weakened a anticyclonic circulation in the bay head which had a significant role in material transport on the bay scale, and consequently promoted hypoxia inducing increase of nutrient elution amounts from the seabed and material cycle in the bay. Moreover, simulation results indicated that coastal landform change could influence on not only currents and water quality in the bay but also mass balance of the adjascent seas, and that reclamation of seaweed bed was not effective in water quality improvement in the bay head.

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 We examine inter-annual and inter-seasonal effects of the fluctuating Kuroshio path, sea-surface wind and tides on circulation and larval dispersal in the Seto Inland Sea (SIS) using a massive amount of Lagrangian particles released in the modeled SIS circulation field with a double-nested, high-resolution ROMS-based SIS model for the years 2007-2014. When the Kuroshio path is close to Cape Ashizuri but far from Cape Shionomisaki, the clockwise SIS throughflow associated with the SSH difference between Bungo and Kii Channels is enhanced to transport more larvae eastward. Consequently, inter-annual variability of larval dispersal is largely affected by the fluctuating Kuroshio path. Northwesterly winter monsoon promotes direct eastward transport of larvae while resultant southwestward Ekman transport also play a role in the western side of the SIS. Tidal currents substantially reduce eastward larval transport through strong vertical tidal mixing that leads to downward larval transport across the pycnocline.

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 We evaluate sensitivity and robustness of larval dispersal patterns to particle tracking parameters (the number of particles and the particle release depth) and to configurations of circulation model (horizontal resolution and output interval), using a triple-nested, high-resolution Seto Inland Sea (SIS) circulation model coupled with an offline Lagrangian particle tracking model. The optimal number of particles is evaluated 8,000 in inner bays while 12,000 near the mouth. Although the depth of initial particle displacement relevant to vertical migration of spawned larvae is less influential, refinement of lateral grid resolution in the circulation model is essential to realistic larval dispersal patterns due to better representation of complicated flow structures near coastlines and straits. Inclusion of transient tidal forcing is substantial to enhance the robustness, even as residual effects through the daily-averaged circulation field.

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 Minamata Bay which suffered from a major disaster called “Minamata Disease” has already remediated from 1977 to 1990 by carried out highly mercury (Hg) contaminated sediment and reclaimed it in the bay area. Furthermore, many studies reported that the mercury has reached Yatsushiro Sea, the outer part of Minamata Bay. It can be assumed that the sediment transport still occurs from remaining Hg concentration even after the remediation project. In order to investigate it, we try to simulate the transport of sediment contaminated by Hg from Minamata Bay to the Yatsushiro Sea with different coastal morphology on before and after the reclamation projects.
 Sediment transport and tidal flow with rectangular variable grid both before and after reclamation conditions around the Yatsushiro Sea and Minamata Bay are simulated by DELFT3D. The initial bottom sediment thickness of 1m is set in the only inner side of the bay and six months simulation results for both before and after reclamation area are compared. The change of hydrodynamic condition inside Minamata Bay due to the remediation project gives a slight change in sediment transport pattern. It is estimated that after the reclamation, the sediment transport moves slower than before it due to the change of its magnitude of velocity above the seabed. As an important result, it is clarified that a change of the amount of bottom sediment which can be re-suspended in Minamata Bay caused by the topographical change can also affect the pattern. Also, this result suggests that the southern part of Yatsushiro Sea can be influenced by sediment contaminated by higher Hg included before the reclamation project.

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 The authors performed field surveys, collecting surface and core sediment samples at 39 stations at the head of Tokyo Bay in 2014 and 2015, to analyze spatial and temporal variation in sediment quality during the past three decades. Sediment quality, such as grain size distribution and TC, was measured along with radiations of Pb-210 and Cs-137 for determining age of sediment. Collected sediments were classified into four groups through a cluster analysis and characteristics of sediment variation were identified, such as the appearance of maximum TC at the surrounding area of the center at the bay head and significant influences of the distance from major rivers and coasts, sediment accumulation rates, and a frequency of exposure to hypoxic water. TC values took peak around 1980s, then decreasing and recently they have a tendency of restoring to high values, which tendency is consistent with the recent unsuccessful restoration of water environment in terms of hypoxia.

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 In order to elucidate a link between SOC and the benthic environment, field observations of water quality and sediment environment were carried out from summer to autumn at 5 sites in the head of Tokyo Bay in 2009 and 2010. SOC was relatively large in off-Makuhari dredged pit and peaked at Ebigawa river mouth. Temporal variation and dominant patterns of quinone were different across stations. The experiment result of long-term oxygen consumption and changing content of quinone before and after analysis speculated that SOC tended to strengthen because increase of microorganism number by decomposable matters, promotion of microorganism activation and strengthening of oxidation of reduced substances in the sediment when bottom water is provided oxygen from upper layer. SOC afterward reduces due to decrease of microorganism number and elution suppression of reduced substances.

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 Radioactive materials were released from the Fukushima Daiichi Nuclear Power Plant as a result of the reactor accident after the 9.0 earthquake and subsequent tsunami of 11 March 2011. The radioactive cesium density in the Edo-river and the inflow amount of the radioactive cesium from Edo-river into the Tokyo Bay were estimated quantitatively. And, amount of sediment of radioactive cesium was estimated quantitatively in estuary area and front sea area of the mouth of Edo-river.

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 We carried out numerical studies for sediment discharge from a large scale river mouth. The numerical method is not a traditional advection-diffusion of sediment but an individual tracking of sediment particles influenced by river discharge and density current of sea water. The particle tracking scheme considers flocculation effects due to mixing process of river water and sea water, leading to enhanced settling of sediment eventually. Numerical parameters for the flocculation processes are estimated by a laboratory experiment. We confirmed that starting time of flocculation changes depending on river discharge and finally effects level of flocculation and distribution of deposition of sediment on sea bottom.

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 Biodegradability tests were conducted and refractory organic carbon in the sediment of an artificial salt marsh was seasonally examined because of increasing demands for the knowledge of carbon storage at the salt marsh. The results revealed that 45.9 - 77.0% of the sedimentary organic carbon were refractory organic carbon at the intertidal area, while the refractory organic carbon increased up to 92.5 - 98.3% at the submerged area. A rough estimation of carbon storage at the upper 5 cm of the sediment was 9.5 ton C for intertidal area and 27.6 ton C for submerged area of the north salt marsh of Osaka Nanko bird sanctuary.

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 Soil particle surface has negatively charge. Characteristics of organic mud change with adsorption of cation and organic matter has been reported. Understanding of transport and deposition of organic mud, we proposed a new measuring method of adsorption ion of organic mud. Moreover, we cleared that liquid limit varies because of the changing the type and cation concentration and ion concentration of pore water.
 Amount of adsorption cation was measured based on the cation exchange capacity test. Adsorption cation of the sediment located at the tidal river and sea bottom were almost Ca²⁺, Na⁺, K⁺ and Mg²⁺. The ratio of adsorption cation was same and adsorption cation varies with amount of clay and silt. In the 90 % cations adsorbed on the organic mud changed to Ca²⁺, liquid limit of the mud decreased about 10 %. The pore water changed sea water to fresh water, liquid limit of the mud increased about 10 %. These phenomena can explain thickness of electrical double layer.

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 Sediment microbial fuel cell (SMFC) can improve decomposition of organic matter in sediments; however, there are some problems such as low rate of electron transfer and decrease in pH of sediments. In this study, we aim to understand effects of granulated coal ash (GCA) on increasing electron transfer rate, increasing pH, and fixing nutrient salts in SMFC through laboratory experiments. Sediment was collected from a coastal region that affected by wastewater discharge, and used as fuel in SMFC. At the end of experiment, we analyzed and compare pore water and overlaying water qualities, and sediment properties of each case. As a result, mixing GCA with sediment increased electron transfer rate, protecting the decrease of pH by electron recovery, and fixing the nutrient salts released during decomposition of organic matter, specifically fixing PO₄. Furthermore, SMFC can make GCA to be more effective in fixing the nutrient salts, and decomposition of organic matter within SMFC is enhanced after mixing GCA.

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 Sediment microbial fuel cell (SMFC) can improve decomposition of organic matter in sediments; however, there are some problems such as low rate of electron transfer and decrease in pH of sediments. In this study, Effects of steel slag on increasing electron transfer rate, increasing pH, and fixing nutrient salts in SMFC were examined through laboratory experiments. Sediment was collected from a coastal region that affected by wastewater discharge, and used as fuel in SMFC. At the end of experiment, pore water and overlaying water qualities, and sediment properties of each case were analyzed and compared. As a result, mixing steel slag with sediment increased electron transfer rate and protected the decrease of pH caused by SMFC. Furthermore, SMFC enhanced dissolution of steel slag, making steel slag to be more effective.

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 Sediment microbial fuel cells (SMFCs) can remediate sediment that vanish water environment, in concurrence with electricity generation. Unfortunately, power produced by SMFCs is still low because of energy losses (overvoltage) such as activation loss and mass transfer loss, which weaken the practical use of SMFCs.
 In this study, we proposed some methods for reducing internal losses of SMFCs, such as electrode design and the use of bamboo powder. The SMFCs using these methods were performed in a tidal river. We found that spreading electrode and mixing bamboo with sediment could reduce the overvoltage of SMFCs, providing a higher performance of SMFCs.

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 Anaerobic digestion in organic matter-enriched sediment forms a strong reduced environment which inhibits benthos living. Here, we aim at examining the growth and type transition of algae in a strong reduced sediment through field experiments. We supplied electron acceptors to the sediment to lower the reduced condition of the sediment. The supplying method is the same to that of used in shallow regions (e.g., tidal flat) in combination with the construction method of using alkaline material (i.e. granulated coal ash) as a basement. Experiment results showed that supplying electron acceptors induces to the growth and type transition of benthic flora, fauna and algae. We also revealed correlations of the transition of benthic algae with benthic flora and fauna, and with the quality of water and sediment.

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 Oxygen radical absorbance capacity (ORAC) was applied to brackish water bivalve Cobicula japonica to assess oxidative stress responses to water temperature and salinity as natural factors, municipal wastewater as an anthropogenic factor, and suspended solids (SS) as its food source. The changes in water temperature and salinity led to drop in ORAC within two days. In contrast, wastewater exposure increased ORAC within the same days. Particulate matters in municipal wastewater would have an influence on the synthesis of antioxidants. However, ORAC was recovered to the initial level among any factors in less than one week from the start of the experiment. The results revealed that the brackish water bivalve was presumably adapted to the environmental changes. The response experiment to SS showed that SS was sensitive to the behavior of ORAC. Particularly, carbon content in SS was found to be important to synthesize and maintain antioxidant in the bivalve.

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 This study examined the environment characteristics of each sea area by past studies of the Yathushiro Sea, correlation of bottom sediment environmental characteristics and macrobenthos distribution, mean currents of undermost layer, time series variation of nitrogen and phosphorus in water quality and bottom sediment and clustering of water quality, bottom sediment and benthos species. Result of examination, the Yatsushiro Sea can be divided into seven sea area divisions.
 This study is to be a valuable reseach in order to examine measures of restoring of polluted sea area.

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 The awareness of coastal blue carbon is increasing, and the dynamics of the CO₂ fugacity (fCO₂) in shallow coastal waters are becoming critical for evaluation of CO₂ fluxes. We carried out numerical computations using a three-dimensional environmental flow model including snowmelt-related groundwater discharge and estimated fCO₂ in water from salinity, biological metabolism, and calcification. Under the influence of the low salinity from the growndwater, fCO₂ in water was found to increase slightly as a result of the opposite effect of a decrease in fCO₂ with decreasing DIC and an increase in fCO₂ with decreasing TA.

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 The Kuroshio is one of the most energetic western boundary currents accompanied by vigorous eddy activity both at meso- and submesoscales which significantly affect biogeochemical productivity in the upper ocean. We examine such processes with a climatological ocean modeling based on ROMS coupled with an NPZD model for the Kuroshio region off Japan. Cyclonic mesoscale eddies develop in the coastal area of Enshu Nada, leading to upward nutrient supply to euphotic zone with promoting active primary production. In contrast, Chl.a is much less prominent around the Kuroshio path where the higher EKE is distributed. The downward eddy-induced vertical nutrient flux occurs at depth beneath the Kuroshio path and the reduction of nutrient consequently takes place. Therefore, a substantial amount of nutrient is removed from the near-surface layer by eddy-driven downward nutrient transport, resulting in suppressing the primary production there.

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 Transport processes of larval marbled sole (Pseudopleuronectes yokohamae) from the spawning ground to the juvenile habitat via a floating larval piriod are estimated by the ocean modeling in order to understatnd the ecosystem networks of the larval fish surveyed in Osaka Bay. The field surveys in 2014 showed that the floating larvae were a lot and widespred in Osaka Bay on later half of January though they were little on early January. The spawning grounds of the observed larvae are estimated using the two-way particle tracking model (PTM) combined the forward-in-time PTM with the backward-in-time one. The backward-in-time PTM results indicate that the spawning grounds of the observed larvae are only Osaka Bay and the neighbor area such as Harima Nada, Akashi Strait, Kitan Strait and Kii Channle. Furthermore, the results of forward-in-time PTM which particles run off from the spawning ground assumed with the backward-in-time one reveal that the origins of the observed larvae are mainly Osaka Bay though about 20% larvae at a survay station in the closed section of the bay were transported from the outside areas such as Akashi Strait and Harima Nada.

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 The larval Japanese anchovy Engraulis japonica (so-called “shirasu”) enter the Osaka Bay from the Pacific Ocean every end of April, and the catch reach its peak in May. The Japanese anchovy is important fish species both of ecosystem and fisheries. We constructed a coupled model of primary ecosystem and particle-tracking of shirasu, and it is examined that the production rate of shirasu affected by which of the nutrient loading into Osaka Bay and quantity of recruitment from the open ocean. Consequently, when the nutrient loading changed 0.5 times and 2.0 times from basis case, the rate of variability which the shirasu production rate is 0.15 to 0.26 for rate of loading change. On the other hand, when the recruitment of shirasu from the Kii Channel decreases 0.3 times, it reach 0.34 for rate of recruitment change. Comparing to the production rate variation of shirasu to each two factor, it is suggested that its production rate more depend on the quantity of recruitment into Osaka Bay than the nutrient loading fluctuation in this bay.

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 The present study aimed to investigate the impacts of the hydrodynamic flow on the phytoplankton biomass in Kesennuma Bay, Japan by continuous monitoring of the vertical distributions of flow and water qualities (water temperature, salinity, and Chl-a) at the narrow chnael in the bay during March 2014 to June 2015. Residual flow and residence time were estimated +10 ～ -40 mm/s and 11 days respectively. The inflow from the Pacific Ocean to inside of the bay dominated from October 2014 to March 2015 from all depths, while the outflow dominated during April to September 2014. Chl-a was transported from the Pacific Ocean to inside of the bay during March to May 2014 and December 2014 to May 2015, and the mixamum Chl-a inflow from the Pacific Ocean was observed during March to May 2014. On the other hand, Chl-a was transported from inside to outside of the bay during June to November 2014. The temperature-salinity diagram suggested the inflow of the Oyashio water from the bottom layer during 2014 spring. Thus, the approaching and flowing southward trends of the Oyashio current were thought to highly contribute to the supply of abundant phytoplankton into the Kesennnuma Bay.

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 In coastal area of Toyama bay, the fresh water with rich nutrient from rivers joins the Tsushima warm water entering from the open sea with high salinity. Thus, the fine oceanic environment is formed and aquatic resources are rich. Recently, however, it becomes important to understand the distributions and variations of ecosystem because of a change for the worse of its environment. Accordingly, we analyzed the observational data of chlorophyll a in Toyama bay coastal-area and investigated its vertical distribution and its changing using one-dimensional ecosystem model (NPZ model). As a result, it was found that the turbulent mixing affected the vertical distribution of phytoplankton in Toyama bay significantly.

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 Artificial tidal flats are constructed using dredge soil with high silt-clay content, which is generated during the dredging of port channels and anchorages. Experimental tidal flats were constructed in the sea to investigate the positive effects of these habitats on short-necked clam populations. Sulfides generated in the bottom sediments, even at a very low level, reduced the survival rate of clams, and temporal variations in survival rates could generally be estimated from the monthly total sulfide production.

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 To clarify the applicability of recycled resources as ground material on a pro-environmental seawall, we conducted the verification test that covered the sediment with a ferronickel slag (FNS) and a granulated coal ash (GCA) at the pro-environmental seawall. In this study, we focused on the characteristics of FNS and GCA as habitat for manila clam Ruditapes philippinarum, especially. Though the competing species abundance at the FNS area were higher than the sand area, the mamila clam abundance was comparable with the sand area. Therefore, we considered that the FNS function as habitat for manila clam was equivalent to the sand. The mamila clam abundance at the GCA area was smaller than the sand area owing to a limitation of the bottom reaching rate of the juvenile due to the coarse grain size. However, the growth rate of manila clam at the GCA area was faster than the sand area due to the efficient food (benthic algae) supply and reducing the hydrogen sulfide. The GCA was expected to use as groud material at the protective zone for manila clam.

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 We conducted a monitoring study of artificial tidal flat in Yatsushiro Port. We found out the influence to biological communities from the competitive organisms and sediment . In the evaluation management of flats, there is a need for such a comprehensive perspective. Various bottom sediments of artificial tidal flats, complicates the biological relationship to each other, improve biodiversity.

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 Spatial prioritization for conservation of the biodiversity of threatened brackish gobies is imperative. Therefore, we conducted field surveys at 189 riverine estuaries flowing into the Seto Inland Sea and prioritized estuaries for conservation by using Marxan analysis. For the case in which the entire area of Seto Inland Sea was set as the target area for conservation, it was revealed that the top 47 rivers cover more than 50% of the habitat of all goby species.

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 Barren ground is widely distributed in the sea area. The growth of seaweed is effected by water temperature, wave height, solar radiation and other environmental factors. And feeding pressure of sea urchin is also important to predict seaweed growth. In this research, from field survey of thrown stone reef and breakwater structure that has reef steps, change characteristics of seaweed amount and sea urchin number are clarified. Seaweed amount of thrown stone reef are smaller than that of rear steps. By improving the prediction method in the rock reef area, estimation method of seaweed amount in thrown stone reef are developed.

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 A sea glass species. Enhalus acroides is an endangered species distributed over Iriomote island. The physical external force were simulated using the wave model (SWAN) . in every month for 1 year. The simulated distributions of monthly averaged H_1/3 and bottom current velocities were compared with the plane distributions of E.a. observed in 2013. The distributions of E.a were reproduced in excessive areas using in calm condition in June. and could be reproduced more correctly using in rough condition in typoon and winter season. E.a. were decreased from 1989 to 2013. in the outer part of H_1/3 and bottom current velocity.

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 This study was conducted to clarify the relation between coral distributions and physical variables in Sakiyama Bay, Iriomote Island, Japan. First, distributions of coral coverage by the colony shapes and coral areas by the community types were investigated at 72 points around the bay. Next, results of numerical simulations for the physical variables such as oceanic flow and soil particle numbers under average summer and winter conditions in the region were analyzed and compared with the obtained coral distribution.
 The results are summarized as follows: 1) Coral coverages show a direct relation with bottom flows in the region, and the bottom flows differ with coral community types. 2) Coral coverages show an inverse relation with soil particle numbers in the region. Enhalus acroides mainly inhabit the region with a larger number of soil particles.

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 We elucidated seasonal dynamics of the CO₂ flux in reed salt marsh of Yodo River. The CO₂ flux by eddy correlation method observed 0.90 mgCO₂/m²/s in the daytime on spring and reed salt marsh absorbed CO₂. On the other hand, CO₂ was emitted in the daytime on summer. Relating to the CO₂ flux, the latent heat flux and sensible heat flux were also observed seasonal dynamics. CO₂ detected by bulk method constantly emitted at water surface in all season. CO₂ emission rate in sediment measured by chamber method were high on spring and autumn. It was revealed that CO₂ flux had seasonal changes.

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 In order to examine the evaluation method of CO₂ exchanges of the artificial salt marsh in urban coastal area, CO₂ exchange of the intertidal flat and the sea surface were reviewed based on the measurement data by chamber method at Osaka nanko bird sanctuary in 2014-2015. Furthermore, the sea bottom CO₂ emission was measured by conducting laboratory experiment using the sediment. After the gross photosynthesis rate of microalgae on the intertidal flat was approximated by three type models, it was suggested that CO₂ absorption rate of the intertidal flat is able to estimate by the sediment temperature and the light intensity. It was thought thatCO₂ emission of the intertidal flat is able to be expressed as a function of the sediment temperature. On the other hand, it is found that the measurement data by chamber method and the estimation data by bulk equation must be used selectively according to wind condition in order to estimate the air-sea CO₂ exchange. Finally, it was thought that the sea bottom CO₂ emission is desirable to estimated from the data of time variation of DIC concentration of the sea water.

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 We developed a new stated preference approach that was named rank comparison method (RCM) for evaluating multiple ecosystem services in a tidal flat easily. We conducted the internet survey to the citizen at the Tokyo Bay Basin, and inquired about the ranking of economic value of evaluating services compared with the reference services. The economic values of reference services were decided using market value approach or revealed preference approach. Based on the ranking of evaluating services and the economic values of reference services, we estimated the economic value of evaluating services. In addition, the economic values of evaluating services were converted into the individual economic values at the four tidal flats by use of the quantitative scores that were based on Ocean Health Index and assessed by the biological or sociological metrics.

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 We estimated tsunami mitigation effects of coastal forest, multiple countermeasures, and its combination by tsunami numerical analysis and actual damage data in Iwanuma City. Our results demonstrated that coastal forest could delay the tsunami arrival time at around the Sendai-Tobu Road by a maximum of three minutes. Reduction of building damage probability and fatality ratio in all areas other than Yanome District can be confirmed. Furthermore, scenarios focused on a multiple defense system were also considered in our hazard assessment. As results, the current multiple defense system shows tsunami mitigation effect. Configurations and combinations of the multiple defense system could increase the mitigation effect. Tide embankment decreases inundation of tsunami, and hill decreases flow velocity of the rear. Multiple defense system utilizing these characteristics with the combination is effective for tsunami mitigation.

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 A long-term assessment of storm surge using the stochastic typhoon model (STM) is one of the secured methodology with the large number of samples of the reproducibility is desired if we can estimate storm surge from STM. This study has improved statistical maximum storm surge model, which uses only typhoon information, in the three major bays using artificial neural network (NN). In order to estimate long-term changes in storm surge characteristics under future climate conditions, NN uses STM and climate database for Policy Decision making for Future climate change (d4PDF). The long-term impact assessments of storm surge using several scenarios are compared.

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 This study examined long-term ensemble projections for historical and future climate conditions over 5,000 years by atmospheric global circulation model. The future climate condition is assumed as a constant +4°C of global mean temperature and present climate condition is perturbed by observed SST error. A set of ensemble experiments makes impact assessment of low probability phenomena such as tropical cyclone and storm surge in comparison with conventional time-slice experiments. Future changes of storm surges will be severe at 15-35°N in the northern hemisphere, especially around East Asia region. In addition, future changes of regional storm surge targeting Tokyo and Osaka bay give +0.5 m increase of storm surge height at a 100-year return period.

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 High-resolution 60km-mesh atmospheric general circulation models (MRI-AGCM 3.2H) and even finer resolution models have been developed and used to investigate potential future changes in tropical cyclone activity due to the global warming. In order to consider uncertainity in projecting future climate change, multi-physics, multi-SSTs, and multi-intial conditions ensemble simulations are conducted, however, therer are still unignorable bias remains in GCM simulations. In this study, we use the statistical bias correction method that we developed for these ensemble simulation output and use the ensemble data for storm surge model to project future storm surge change. This study indicates that storm surge around Japan would likely shift to the east in the future.

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 In order to evaluate the uncertainties on typhoon intensity and storm surge due to the differences of global warming scenarios (GWS) and general circulation models (GCM), pseudo-global warming ensemble experiments are conducted using the high-resolution typhoon model (HTM) and storm surge model (SSM). Typhoon Haiyan (2013), which caused a severe storm surge around Leyte Gulf in Philippines, is seleceted as the worst case of a typhoon in present climate. The standard deviations of typhoon intensity and storm surge due to the difference of GWS are 4.6 hPa and 0.18 m, respectively. On the other hand, the standard deviations due to the difference of GSM are 8.9 hPa and 0.39 m, respectively. The results suggest that the uncertainty of GSM is larger in the target case than that of GWS. It is concluded that to project the future storm surge using the GSM, HTM and SSM, the GSM-derived data should be avaraged before feeding HTM which contains strong nonlinearlity.

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 This study developed an integrated model of long-term assessment for storm surge height based on typhoon maximum potential intensity and simplified storm surge modeling. Climatological parameters were related to explanatory variables of storm surge. Storm surge caused by Typhoon Vera (1959) was analysed for validation, and sensitivity analysis found that the most sensitive parameter is wind speed for the integrated model. Then, we calculated maximum possible storm surge height of three major bays in Japan by applying both present and future climate condition. If global warming is represented by SST (sea surface temperature) rise only, sensitivity of storm surge height against SST is about 0.8-1.5 m/°C for these bays.

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 The object of this study is to numericall investigate atmospheric and oceanic environments mainly governing the intensity of a typhoon and its storm surge. An individual effect of sea surface temperature (SST), stratospheric and tropospheric air temperature (SAT, TAT), and relative humidity (RH) to intensity of typhoons and storm surges are investigated, via making use of pusedo global warming methodology employing 26 Global Climate Model results of CMIP5's RCP 8.5 scenario. As a result, the change in both SAT and TAT can cause to decrease a typhoon and its storm surge intensity. One of the reasons is that latent heat flux above ocean can be dampeded by high air temperature in lower troposherer. Furthremore, the expected small increments of RH have relatively a little influence on the intensity of typhoon, compared to those of SST, SAT and TAT. As a conclusion, it can be said that future environments composed of both low TAT and high SST have a positive inpact on the high intensity of a typhoon and storm surge.

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