A large amount of sand was deposited in an area between the north breakwater and a jetty of Katakai fishing port, and it was calculated to be 7.7×10⁵ m³ in total with the mean rate of sand deposition of 4.5×10⁴ m³/yr between 1994 and 2011 on the basis of bathymetric survey data. This rate is in good agreement with the value of 4.9×10⁴ m³/yr calculated from the numerical simulation using the contour-line change model. Furthermore, southward longshore sand transport turning around the tip of Katakai fishing port has been trapped, resulting in the excessive deposition of sand in an area immediately south of north breakwater because of the extension of a jetty of 650 m length.

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 The controlling effect of longshore sand transport using groins (ordinary-type, groin of low-crown height, groin with an opening near the shoreline, submerged, slit-type groins) was investigated using the BG model (a three-dimensional model for predicting beach changes based on Bagnold' concept). When the landward end of the groin is located at the shoreline, the rate of passage of longshore sand transport is as high as 74%, resulting that almost all longshore sand transport discharges downcoast while losing the groin effect. This condition corresponds to the case in which an opening is formed at the landward end of a groin as a result of shoreline recession. Furthermore, in case of slit-type groin, the rate of longshore sand transport increases because of the passage of longshore sand transport through the slits, and its effect is low.

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 In the area with 5 km length between Yoshiwara and Nyuzen fishing port on the Shimoni-ikawa coast, the width of the offshore shelf gradually narrows with the development of submarine canyons. In particular, near Nyuzen fishing port east of the Kurobe River, a very deep canyon develops very close to the shoreline. Part of westward longshore sand transport could have discharged via the submarine canyon, and this prevents the recovery of sandy beach by beach nourishment. In this study, the mechanism of sand discharge into submarine caynon was investigated using the bathymetric survey data since 1965, and numerical simulation using the BG model was carried out to consider the measures to prevent sand discharge into submarine canyon.

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 Roberts Bank tidal flat, which is located at the mouth of the Fraser River, has been wellknown as one of the world's largest tidal flats for migratory birds. In the previous studies, biofilm, which exists in a lower salinity region, is found to be significant source of nutrients. However, it has not been revealed how infiltration flow influences salinity inside of a tidal flat. We thus conducted field observations of salinity at the depth of 0.2 m from tidal flat surface. Additionally, in order to clarify horizontal distribution of salinity, two-dimensional salinity model was proposed in this study, which shows very good agreement with field observation results.

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 After the earthquakes have happened in April 2016, a large amount of cohesive sediments have flowed into the Shirakawa river mouth delta due to heavy rains. It was found by field observations that the clinoform in the infralittoral zone moved forward at about 100m from 2014 to 2016. Simple flume experiments were conducted in an acrylic–walled flume. A mix turbid water of water and mud was fed along the bottom bed with a constant discharge. Both of velocity values and suspended sediment concentration values were measured at the same time. The horizontal velocities were accelerated due to turbid waters. That was remarkable for high-concentration turbid waters. Settling velocity is increasing with the increase of the salinity and the mud concentration. But it has a maximum value around 16000ppm of the mud concentration.

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 To elucidate relationships between CO₂ absorption and emission rates and properties of sediment at Yodo River mouth tidal flat was conducted in this study. Similarly, CO₂ fluxes (CO₂ absorption and emission rate) were also measured using light and dark chamber. Chemical properties of sediment such as Chl.a, ORP, AVS fluctuated and maximal values were different season throughout the year. There is a negative correlation only between ORP and soil temperature. The CO₂ absorption rate fluctuated 0.0675 to 6.63 mg CO₂/m² /min, the CO₂ emission rate was 0.038 to 2.82 mg CO₂/m² /min, respectively. They showed maximal values in summer season and were positively strongly correlated with soil temperature, Emission rate in water surface was three times higher than emission rate in sediment. Moreover, it is suggested that macrobenthos respiration contributed to emission rate in sediment.

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 There are both essentially saturated zone (the degree of saturation S_r ≅ 100%) and unsaturated zone in all of the exposed sandy beaches. This geo-environmental characteristics change drastically with a certain value known as the air-entry suction. In natural tidal flats, there are the essentially saturated zones in most of the exposed sediment deposits at the time of low tide, whereas in artificial tidal flats, they may contain unsaturated zones. From the viewpoint of the stability of coastal geo-environments and the conservation of rich ecosystems, it is important to identify the essentially saturated zone in sandy beaches and tidal flats. However, in order to accurately evaluate the zone, it takes time and labor, such as a careful sampling of sediments and laboratory tests of the sampled soils. In this study, focusing on a soil moisture sampler applying vacuum blood sampling, we proposed a new simplified method that can easily evaluate and verify the essentially saturated zone through laboratory performance tests and field surveys, and demonstrated the practicability and effectiveness of the new simplified method. From now on, it is expected that this new simplified method will be effectively utilized at the site.

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 The growth of phyto and animal benthos in Fukuyama inner harbor is inhibited because of the discharge of untreated wastewater into the harbor. Field experiments and benthos observations are conducted to examine the restoration processes of ecosystem in the harbor. When gravel was used as the basement, the reduced level of the basement was evaded, leading to the growth of benthos at an early stage. And then, the growth of benthos that are more tolerant to organic-enriched sediment was confirmed. However, the ability (e.g., mineral dissolution, adsorption) of gravel in evading the reduced level was low. Therefore, alkaline materials, such as fly ash and slag, can be used instead of gravel for restoring the ecosystem in the harbor that seriously affected by untreated wastewater discharge.

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 It is required to establish a consistent evaluation scheme regarding the estimation of tsunami height caused by the submarine landslide, since the standard framework for evaluation has not yet been established although several calculation models have been proposed and practically applied.
 In this study, we proposed the case of evaluating tsunami height triggered by the submarine landslide with multiple calculation models by setting the detailed profile of the submarine landslide based on the results of literature survey and re-analysis of marine acoustic wave exploration records.
 As a result of the comparison of the tsunami height evaluation by each calculation model, it was suggested that the safe-side evaluation result will be possibly obtained compared with the experimental result and other methods, in the case of applying the "kinematic landslide model".

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 It is required to establish a consistent evaluation scheme regarding the estimation of tsunami height possibly triggered by the future landslide, since the standard framework for evaluation has not been established although case studies of reproduction calculation for the past individual events have been proposed.
 In this study, we proposed the case of evaluating tsunami height triggered by the landslide with multiple calculation models by setting the detailed profile of the landslide based on the results of literature survey and on-site geological survey. In addition to the kinematic method, another approach using a wave source amplitude prediction formula based on experiments was proposed as a method of estimating the initial water level distribution of the landslide tsunami.

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 A large amount of sediment is transported by tsunami. While there are many studies on the amount of sediment transport or bathymetry changes by tsunami under the condition of active sediment transport, there are only few studies in the lower regime. In addition, not many studies have focused on the unsteady processes of bathymetry changes due to the propagation of tsunami. This research aims to evaluate the tsunami force, and to study the relationship between the force and bathymetry changes in the lower regime by movable-bed experiments. It was observed that ripples are formed when waves subsequent to the tsunami front reach the bed. The bathymetry changes can be classified by the method used in rivers. The relationship between the spatial distribution of grain size and shear stress observed in the experiments is consistent to existing studies.

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 Hydraulic experiments were carried out in order to analyze sediment transport and bottom topography change due to tsunami and accumulate the validation data of numerical model for coastal sea area with narrow pass. The experimental results revealed that high velocity flow in the narrow pass caused by tsunami passage induces local erosion. Furthermore, it was also found that suspended sand transported near the narrow pass settles down and forms deposition area behind the structure. The comparison of the results for two kind of shorelines, namely overflow and reflection types indicated that the condition of the shoreline has a strong influence on the flow structure and sediment transport induced by tsunami.

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 This paper examines the behaviour of subaqueous gravity mud flows in a set of centrifuge model tests. Focusing on the high density sediment transport due to the gravity current, we performed 17 centrifuge tests on clay deposits with water content from 80 to 140%. We found that there is a critical point to differentiate flow regime at water content 120%. These are 1) uniform flow of clay and 2) turbidity current of clay. In the former, the flow distance increases with an increase in the water content. In the flow of the latter, the velocity of the flow was maintained and the flow distance was lengthened. This flow mode is considered to be one of long-distance transport conditions of gravity flow with high density.

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 To study the possibility of the appropriateness of artificial gravel made of the coal ash for the material for beach nourishment, the movement of the natural and artificial gravel of the same grain size under waves were investigated using a two-dimensional wave channel experiment. It was found that the berm height was reduced with greater foreshore slope in case of artificial gravel compared with that in natural gravel. Furthermore, the abrasion test of natural and artificial gravel was carried out using Los Angels' machine for abrasion. The artificial gravel was easy to subject to wave abrasion compared with that of natural gravel.

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 In 2002, beach was severely eroded in front of Hamana Bypass at the Arai coast located west of the Imagire-guchi Inlet of Lake Hamana, resulting in the exposure of the seawall protecting the highway against waves, and the possibility of the failure of the seawall increased. As a urgent measure, gravel net was installed along the seawall to protect the foot of the seawall. In this study, field observation was carried out around the gravel net to investigate the change in gravel net in 2016 when 14 years has passed after the installation of the gravel net.

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 This reports on the jetty work using sand packs, and verifies the effectiveness of the jetty work. The sand pack construction method uses bags made of ground fabric which combines high strength woven polyester fabric with artificial turf, filled with local sand or shore maintenance sand. By adopting a raised fabric that takes care of surface wear due to drifting sand and using canvas with anchor tubes for scouring of the foundation sand surface, it was possible to make the structure highly stable near the shore exposed to the waves. The coastal condition around the jetty work was continuously observed by surveillance cameras, and the effect of the jetty work was verified in one year and five months after construction.

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 Hydraulic experiments were conducted using two-dimensional wave flume to clarify the characteristics of clay slip-out behavior under mixed sediments with different wave conditions and clay fraction. The results showed the mixed sediments exhibit the similar behavior of pure clay in the high clay fraction condition. From the results, it was implied that there is a threshold of clay fraction between pf =0.10 and pf = 0.20 to determine whether clay- or sand-dominant behavior. Moreover, the formations of a flow path near the surface and sublayers in the bed was confirmed with the vibration of different cycle according to the wave period in the case of pf = 0.20, and this flow path accelerate slip-out phenomenon of clay. Therefore, the significance of considering clay slip-out phenomenon is suggested to analyze characteristics of dynamic behavior of mixed sediments.

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 Sampling methods involve destruction of sediment and they cannot be implemented in high frequency. Therefore, in this study, we have developed and proposed a time continuous monitoring method of sediment porosity change under wave action. The monitoring system consists of usage of inexpensive electrical resistivity sensors and calibration technique that is based on porosity-electrical resistivity logarithmic relationship. The compaction effect of suction dynamics on swash zone has been examined through a experiments by using the method proposed in this study.

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 The three-dimensional (3-D) behavior of a sloping-top caisson floating near a fixed existing caisson was investigated using a 3-D coupled fluid-structure-sediment-seabed interaction model (FS3M). From comparison with hydraulic experiments, the predictive capability of the FS3M was demonstrated in terms of the amplitude of the motion of the caisson except for the yaw. Numerical results showed that the offshore and existing-caisson side of the bottom of the caisson can contact with the mound, suggesting that 3-D analysis capable of assessing the pitch of the caisson is essential.

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 Many numerical methods have been developed to estimate wave response of moored floating body and applied in practical design. However, they need some assumptions for behavior of mooring chains and such assumptions were sometimes difficulty for practical application.
 In this study, a new method is developed to solve such problem. The method can simulate detailed behavior of mooring chains with new chain models based on direct and physical phenomena compared with past models.
 The developed method was applied to three different cases which have been investigated theoretically or experimentally. Simulated results were compared to these existing results, and the results showed that the present method can simulate well the behavior of a floating body moored by chains even the chains are grounding and/or slacking.

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 This paper describes results of numerical investigation on dynamic amplifications of fairlead tension using time domain analysis focusing a mooring chain of Floating Wind Turbine in about 100 m water depth. By time domain analysis in which mooring chains are excited by horizontal and sinusoidal displacements at the fairlead with various frequencies, we investigated tension time histories and movements of segments of lines and analyzed dynamic effects associated with the nonlinear damping and added inertia force acting on line segments using simplifying linearised catenary theory , and suggested methods to evaluate the effect of hydrodynamic forces on line tension by using fairlead displacements obtained from quasi- static analysis.

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 This paper proposes a large-scale floating coal transshipment station (LFTS) for loading, storing, and offloading coal. This paper discusses LFTS static stability and its elastic deformation characteristics during coal loading operations. It will act as a relay base for barges and bulk carriers. Installing an LFTS offshore from East Kalimantan is expected to improve coal transport productivity in Indonesia. The proposed LFTS can have a total storage capacity of 500,000 tons, and size was set to 590 m × 160 m. In this study, due to the compartments, coal loading conditions can vary significantly and affect the local static deflection, so we modeled the overall deformation and rigidity under various operational scenarios. The results were compared to the allowable material stress to identify conditions that will produce material failure. Moreover, we evaluated operation in the shallow Kalimantan River, since the weight of loaded coal deepens the LFTS draft, reducing the clearance between the LFTS and sea bed. We found that this reduced clearance and large added mass impact the natural frequency of the LFTS. The natural frequency exists in the low frequency band, and tuning with the wave is also expected, and we tried to grasp the influence of the coal loading conditions on the vibration characteristics of the LFTS.

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 Direct measurement of sea level at Meshima Island during February 10 – March 27 in 2012 and at Uji Island during February 1 – March 31 in 2016 were made in relation to the occurrence of secondary undulation at the west coast of Kagoshima. We found that the secondary undulations with the periods of 12 and 24 minutes at Koshiki Island and the period of 16 minutes at Makurazaki are dominant. Moreover, it was suggested that the monitoring of sea-level variation with the periods of 8 – 32 minutes at Meshima Island and Uji Island is useful to the prediction of the approach of long-period wave to cause the secondary undulation at Koshiki Island and Makurazaki.

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 Fundamental characteristics of seiches observed around Japan became clear in the previous paper. Seasonal variations of frequencies of seiches at most stations in the whole country are very similar except some stations situated in Hokkaido, Okinawa and inland sea areas. On the other hand, secular variations vary according to stations. Characteristics of two neighboring stations do not necessarily resemble. On the contrary, those of two remote stations are sometimes similar.
 In this paper, all stations are classified into three groups using the probability density function of frequencies of seiches and the similarity coefficient of seasonal variations. The similarity of the seasonal variations has close relation to the shape (the maximum value) of the probability density function.
 As for stations whose annual changes are much larger than neighboring ones, the tendencies of secular variations do not show good agreements with those of other stations.
 It is suggested that the mean magnitude of seiches for many years is not necessarily a stable index for some stations.

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 This paper showed and analyzed low frequency sea-surface motions due to the 2016 Fukushima-off earthquake with its magnitude 7.4 occurring at about 30 km off Fukushima Prefecture at 5:59 (JST) on November 22, 2016, observed by the NOWPHAS (Nationwide Ocean Wave information network for Ports and HArborS) network operated by the Ports and Harbors Bureau of the Ministry of Land, Infrastructure, Transport and Tourism. Propagation and deformation characteristics of low-frequency waves in the Tohoku region along the Pacific Ocean from the offshore to the coast were examined. Spectrum responses from outside the port to inside were almost the same as those of the past earthquake events in each sea area.

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 The Ayerwaddy Region of the Republic of the Union of Myanmar, facing the Bay of Bengal and the Andaman Sea, was hit by Cyclone Nargis in May 2008. The cyclone caused a huge storm surge and brought about 140, 000 death or missing.
 The Project on Establishment of End-to-End Early Warning System for Natural Disaster in the Republic of the Union of Myanmar has been conducted by Japan International Cooperation Agency(JICA) to mitigate such disaster which would be caused by a cyclone at the coastal area of Myanmar. The authors participated in this Project and found it is important to transfer technology to observe and predict tide level more precisely using a harmonic analysis in the coastal area so that residents can take proper evacuation actions well before a storm surge hits.
 The authors therefore introduced a simple observation and prediction method of tide level with the survey ribbon rod and installed at 3 places which suffered the damage caused by Cyclones.
 Furthermore, the author established the tide prediction method not only with the 10 constituents by short term observation , but also with multiple regression analysis which can be used in both of dry season and rainy season.

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 The power potential of tidal currents around Nagashima Strait were examined in relation to tidal current power generation using the results of ADCP observation and numerical simulation. We found the tidal current power of 2.2 kW/m² in the Nagashima Strait and 6.0 kW/m² in the Kuronoseto Strait. Moreover, it was shown from the results of the numerical simulation for the arrayed 20 tidal current turbines that the daily mean value of extractable tidal energy is 447 MW in the Nagashima Strait and 540 MW in the Kuronoseto Strait. In addition, it was suggested that the amplitudes of tidal currents in the Nagashima Strait and the Kuronoseto Strait decrease 6 cm/s and 11 cm/s, respectively, because of the arrayed turbines.

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 Wind and wave characteristics for offshore wind power utilization were investigated off the Kita-kyushu city sea area based on observed field data obtained from newly constructed offshore observation tower system. This paper shows reasonable setting methods for extreme wave and wind design conditions, by considering with the existing international standard and the Japanese port standard. As a result of simulations, the correlation coefficient between waves and winds was clarified, and it was proved to be sufficiently conservative to combine expectation values of 50 years return period.

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 In the offshore area of Kita-Kyushu city, experimental study for reasonable planning/designing of the offshore wind power generation facility has been in progress. At the wind observation tower in the site, continuous observation of wind, wave, and current has been carried out since 2012 and accumulated data under various sea conditions. In the study area, complicated currents are generated under high wave condition combined with wave induced current, wind driven current, and strong tidal current passing through Kanmon Straits. In this study, numerical simulations of current under high wave have been carried out and examined the characteristics of current by extracting wind driven current.

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 For the purpose of developing tidal power generation using bridge pier, we conducted tidal current observation and calculated the amount of energy that can be acquired by assuming the power generation facility specifications. As a result of the tidal current observation for the Oshima Ohashi bridge, the maximum power generation output shows a value of about 120 kW, and the maximum power generation amount of the day got about 330 kWh/day. This value is about one-third of the initial forecast, and the main reason for this is the fact that after the current was formed at the generator installation site due to the vortex generated at the upstream piers at the time of downward tide, it was suggested that it becomes smaller.

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 In this study, assuming an OWC type wave power plant, wave amplification characteristics in a water chamber installed behind vertical-type dissipater units of permeable type have been studied from both experimental and theoretical points of view. The dissipation effect of reflection waves is also examined simultaneously. It was clarified that the water chamber installed behind the vertical-type dissipater units is very effective for reducing reflected waves and further exciting pumping mode wave resonances in it. The governing parameter that controls both the reflection wave dissipations and the wave amplifications in the water chamber was also studied and clarified.

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 A long-term wave hindcast system, which is composed of MSM(Meso Scale Model) -based winds data sets and a backward ray tracing wave model is applied to estimate its accuracy at each of the 24 measurement stations around the Japanese coastal areas of the East China Sea and the Pacific Ocean. Wind data sets with a high time and space resolution are produced by JMA(Japan Meteorological Agency) and released to the public domain. The wave model is operated on a nested grid with lower and higher space resolution. 12-year hindcast data of wave heights and wave periods at each station are compared with the measured data. Main findings are as follows. 1) The system yields a rather high quality estimate of wave statistics at each station of the concerned areas, but the wave height-related correlation coefficient(WHRCC) which ranges from 0.80 to 0.93 with a mean value of 0.85 is about 0.1 smaller on average compared to the Japan Sea case with a mean value of 0.95. This figure reflects the complicated wave conditions in the Pacific Ocean. 2)Accuracy of the system is higher at the East China Sea coasts of Japan followed by that at the western and northern coasts of Japan facing the Pacific Ocean and is lower at the central coasts. 3)The present system gives a WHRCC which is about 0.05 larger than the previous systems but does not yield a significant improvement for the estimation of wave periods.

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 Shikoku Regional Development Bureau has been operating the long-period wave height prediction system since fiscal 2010 as a countermeasure against long-period wave in the Port of Kochi facing the Pacific Ocean. It predicts long-period wave height by using a statistical relational ex-pression that long-period wave height is proportional to the product of significant wave height and sig-nificant wave period. So it is pointed out that it cannot predict that long-period wave height will increase when it only increase nevertheless significant wave do not develop. On the other hand, an ultrasonic wave height meter was installed at the revetment in the Misato area at approximately the same time as the operation of this system was started. At the time of construction of this system, there was a wave height meter only outside the port, and it was not possible to compare and verify the predicted result in-side the port with the actual measurement, but now it is possible. Therefore, this observation data was also used to verify the validity of the prediction, and this system was improved based on the result.

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 The -12m berth in the Misato District of the Port of Kochi is a facility that has already gone into service before the breakwater completion, and then the cargo handling troubles, which are considered to be caused by long-period waves, have ever occurred when mooring ships. Therefore, we installed a reduction system for low-frequency ship motions as a provisional countermeasure until the breakwater is completely constructed, and conducted the field demonstration experiments. This system has winches equipped with high-strength mooring ropes (Tetron Dyneema ropes) on land in addition to the mooring ropes of a ship. The system has a function to control the resonance by shifting the natural period of the mooring system from the predominant period of the long-period waves. In this paper, we described the results of the five field experiments conducted for moored ships during the handling of cargo from FY2014 to FY2015, and confirmed the effects of the reduction system from the experimental results.

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 In calculating the allowable wave heights of a moored ship in a port, the suggested values in “Manual for Influence Evaluation of Long-Period Waves in Ports” are generally adopted as the allowable ship motions for the six components of moored ship motions. However, in calculating the allowable wave heights for a mooring facility where sea conditions are severe and a general mooring method or cargo handling method is not adopted such as a remote island port on the ocean, it is necessary to set the allowable ship motions with reference to judgment criteria at on-site cargo handling works and also to consider ship motions as well as the tensions of mooring ropes. Therefore, for the ports of Nanboku-Daito Islands located in the east of the main island of Okinawa, we studied the calculation methods of the allowable wave heights of a ship moored to the mooring facilities directly affected by ocean waves by using a numerical simulation method of moored ships.

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 Mooring and detachment work is a fundamental activity of the port. However, if an accidental disconnection of the mooring rope occurs due to some cause, it can be a serious dangerous work. It is very important that we make mooring work safe in an operation where land operators hang or remove mooring ropes.
 We studied on consideration of installing ancillary equipments (mooring post, fender, car stop etc.) of mooring facilities for the purpose of improving mooring and detachment works safety. We summarized the results that can minimize these dangerous factors by provision of information, specifically, with regard to cases where safety mooring and detachment work is hindered due to the arrangement and shape of ancillary equipments of mooring facilities.

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 Zostera bed has the function of forming a rich ecosystem, and various kinds of organisms inhabit. This Zostera bed has been reduced in number due to landfill construction done during the period of high economic growth, and now the NPO corporation and municipalities are developing activities. It is general to evaluate soundness based on seaweed bed area and stock density, but it is thought that it is necessary to evaluate soundness based on the diversity of biological communities in consideration of the function of Zostera bed. This research, the final objective is to evaluate from the viewpoint of biodiversity for the Zostera bed created, this paper we will present the results of the biological survey of Leaf creature and bentos performed on the native Zostera bed, It is aimed to evaluate by various methods of evaluating existing biodiversity and to verify the difference of trends by those indices.

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 Eelgrass grows up from spring to summer while they absorb CO₂. During autumn and winter, the upper stem is separated and is accumulated as CO₂ stock at the sea bottom. Therefore, eelgrass has been paid attention in Blue carbon studies. However, because of the difficulty considering the interaction between eelgrass and flow field, it is difficult to analyze advection and diffusion of CO₂ around eelgrass. This study thus aims to develop eelgrass model by taking into account the interaction between eelgrass and flow field. As a result, we obtained very good agreement with laboratory experiments using eelgrass in a uniform and oscillation flow fields.

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 Aerial photograph monitoring is used for evaluation of the eelgrass field. There is a problem with the method of extracting the eelgrass from RGB image by threshold method. Generally, this image analysis uses training data. This depends on the analytical accuracy and analysis time by the proficiency of the measurer. Therefore, in this research we use the snakes method used in the medical field. In this research, we tried applying this method to the aerial image of the eelgrass field.
 As a result, it was confirmed that the eelgrass field can be extracted at a higher speed and accuracy of 80% than the conventional method.

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 The satellite data and UAV (Unmanned Aerial Vehicle) was used to measure the vegetated area of Ulva spp. in YATSU tidal flat. The vegetated areas of Ulva spp. on 27 Oct. 2016 and 4 Nov. 2016 were measured from the image taken by UAV and its vegetated area were around 80% on both day. And characteristics of spectral reflectance of Ulva spp. were almost same as that of land green plant. Therefore, NDVI indicated a positive value at all area on 27 Oct. however, it indicated a negative value in the range over 90% on 4 Nov. It was confirmed that these differences strongly correlate with water depth. So, it was suggested that it is possible to evaluate the vegetated area of Ulva spp. by satellite data by considering the influence of water depth.

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 Demersal fish was forced to live near sea surface in a eutrophic sea area because hypoxic water was formed near sea bottom. There was no habitat for demersal fish near sea surface in urban canal because all coastal line was formed by vertical seawall. Environment-friendliness seawall is an effective solution because the seawall can provide a habitat for demersal fishes. This study focuses on design requirement of environment-friendliness seawall, especially inhabitable water quality level of DO for demersal fish, we conducted experiments using small aquarium which can control water quality difference in vertical direction. As a result, we found threshold level of DO for Dusky tripletooth gody(Tridentiger obscurus) was lower than other kind of fishes and Dusky tripletooth gody can live without any abnormal behavior in a condition of DO> 1.0mg/L.

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 In the canal located in urban area, the bottom layer becomes poor oxygen due to the influence of the saline wedge and thermocline. The purpose of this study was to clarify the effect of habitable seawall for fish in the canal area. We set up a simple basket to be an evacuation site for fish in the surface and bottom layer of canal, and investigated the fish in the basket. As a result, when the bottom layer became poor oxygen, the bottom fish evacuated to the surface layer, and when the poor oxygen dissolved, it moved to the bottom layer. It was suggested that by setting the habitat of the bottom fish on the surface layer, it functions as an evacuation site for fish.

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 In this study, the creation and management of habitat for the endangered tiger beetle were examined in a sandy shore created for the purpose of habitat mitigation. We found that the following two important factors for its habitat. 1) The elevation of habitat for larvae: Its absolute value varied spatially. However, its relative value was similar among different sites and it would be suggested that the flooding time is related to that elevation. 2) The area with stable elevation suitable for larval habitats: A lot of adults were occurred in the year when that area was large. We propose that we should create and manage the area with stable elevation suitable for larval habitats as large as possible in the shore.

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 An artificial tidal flat was created in 2007, to compensate for the loss of a natural tidal flat, at Okinosu, Tokushima City. However, five years after its creation, it was found that the ecological conditions in the artificial habitat of benthic animals differed vastly from those in the natural habitat, and that the abundance of benthic animals was much lower in the artificial tidal flat.
 We propose that a “sinking event” is responsible for this phenomenon. Furthermore, we have determined that this sinking event is caused by bioturbation of ghost shrimp Nihonotrypaea japonica. Here, we undertook experiments to clarify the effect of N. japonica on the tidal-flat ecosystem. N. japonica generated coarse sediment grain sizes and decreased the abundance of benthic diatoms. Treatment with N. japonica exclusive led to a low-biodiversity assemblage—it is possible that, in places where N. japonica dominates, there is an increase in the abundance of only the organisms that parasitize N. japonica nests.

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 This paper introduces new restoration techniques for applying the world national heritage site Ichkeul in Tunisia, which are cost-effective and have low-environmental impacts. This study were explores two different laboratory tests to introduce of the natural sediments which collected in the Ishkeul lake. The main outcomes of this study as follows: 1) Microbial induced carbonate precipitation can improve the physical properties of natural sediments that collected in Ichkeul lake, 2) Precipitated calcite layer can covered the sediments surface and reduction of the re-suspended effect, 3) Microbial induced carbonate precipitation clay can still survive the benthos.

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 This study examined whether river has an influence on primary producers and consumers by comparing un-eutrophicated coastal lagoons with and without direct river influence (AK: Akkeshi-ko, HN: Hichirippu-numa), based on the carbon and nitrogen stable isotope ratios (δ¹³C, δ¹⁵N), for the sustainable use of the shallow coastal area. The C/N ratios, δ¹³C and δ¹⁵N of organic matters in the both lagoons showed that most of the organic matters were not carried from the land, but were produced within the both lagoons. In particular, nutrients concentrations and standing stocks of primary producers showed that the benthic primary producers depending on pore water DIN in HN, and also water column DIN in AK, were dominant, respectively. In addition, δ¹⁵N values of primary consumers (clam and oyster) were approximately 1.5‰ higher in AK than HN, while δ¹³C values were similar in the both lagoons. The enriched δ¹⁵N values in AK suggest feeding on epiphytic microalgae depending on water column DIN than epipelic microalgae depending on pore water DIN. These results suggest that river inputs contribute to the development of the benthic ecosystem, which utilizes water column and pore water DIN.

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 The field observation was conducted to verify application of the technique using the mesh-type artificial base CORAL NET for restoring a coral community in the Naha port. Sedimentation of silts and existing of algal mat deteriorate settlement condition of coralline algae. To avoid sedimentation of silts, CORAL NET was installed at some distance upper from the seabed, and this installation can improve coral habitat. The highest survival rate (80%) of the settled coral was observed one year after the base installation. Coverage of Acropora spp. and Pocillopora spp. on the base reached 45% during 5 years observation.

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 In 2016, in Amitori Bay of Iriomote Island, we surveyed bleaching of corals at a deep reef slope from the reef margin to 40 m below sea level. Physical environments such as water temperature related to bleaching were also examined. The following major results were obtained:
 (1) The rates of bleaching of all corals exceed 50% at water depths less than 20 m, with 87% (maximum) bleaching recorded at 15 m water depth. (2) The rate of bleaching of tabular corals was extremely high (91%). (3) The rate of bleaching of ramiform corals is 49% even in deep water of 30 m, suggesting that bleaching occurs even deep in the sea. (4) Bleaching occurred after July 24, 2016. (5) No typhoon approached Amitori Bay in July or August 2016. Therefore, water temperatures higher than 30°C continued from August 9 through August 29, which accelerated coral bleaching.

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 In this study, ecological influence assessment, using Propsilocerus akamusi as biotic indicator, of shell fragment as sediment improvement meterial of regional unused resources was conducted. Survival rate of Propsilocerus akamusi were 100% in unsprinkled system (control), 73.7% in 10g/m², 61.9% in 50g/m², 52.4% in 100g/m², 52.4% in 150g/m² and 52.4% in 200g/m² in unburnt treatment system, and 68.4% in 10g/m², 61.9% in 50g/m², 47.6% in 100g/m², 38.1% in 150g/m² and 28.6% in 200g/m² in burnt treatment system. LC₅₀ (50% Lethal Concentration: median lethal concentration) were estimated as 199g/m² in unburnt treatment system and 97g/m² in burnt treatment system, respectively. The optimal application rate of shells as regional unused resources for balancing ecosystem conservation and water quality improvement was estimated to be 100g/m² burned system. Influence of shell sprinkling using multi species including system considering of food chain should be investigated in future study.

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 We laid out the waste oyster shells in a closed harbor area on the western part of Bisan Seto, and researched the change of biota. Various organisms increasing since two months later, they have reached 117 kinds (2.2 times of the control), 4,700 inds/m² (2.3 times) and 487.3 g/m² (13.2 times) for 1.5 years. Resolved carbon was calculated at 114.2 kgC/year/1,000 m². The shells layer kept to be visible, not buried, at sea floor in this period. These results are suggested that the biological activities can make diversity and biomass in the shells layer increase, and keep not covering with organic particles.

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