Influence of extracellular polymeric substances (EPS) secreted by cultivated laver on both transparency and sedimentary stabilization in Ariake Sea was experimentally examined. The laver culture experiment showed a production of EPS (evaluated by total sugar concentration, viscosity and molecular distribution) and showed an increase in dissolved organic carbon (DOC). The powdered EPS recovered from laver increased transparency of the suspension prepared using particles of Ariake sediment and increased a stability of the sediment based on rheological measurement. The results in this study would suggest a contribution of laver to the increase in transparency and in stability of the sediment in Ariake Sea.

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In order to obtain the background information about characteristics of particulate organic matter (POM) in the inner part of Ariake Bay, oxygen consumption rate of bottom water including POM and primary production rate were investigated. Additionally, relationships between biochemical composition of POM and oxygen consumption capacity, controlling factor of primary production were examined. In summary, it was suggested that contribution of oxygen consumption by POM, especially originated from the marine phytoplankton, plays an important role for the formation of hypoxia in the inner part of Ariake Bay. Primary production rate were varied widely among observation dates and it was suggested that nitrogen is limiting nutrient in this are during summer.

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To investigate and verify the mechanism of occurrence of hypoxia in the waters of the inner western part of Ariake Bay, field observations were performed in summer (July to September) 2008. During the observation period, bottom DO decreased at neap tides, especially at the shallow station, and recovered to higher levels during spring tides. The hypoxic waters in the inner western part of Ariake Bay were essentially generated at two points: around the subtidal (between stations T1 and T14) and in the deeper offshore zone (around station P6). In some cases, hypoxic waters were found from stations T1 to P6 along the submarine valley of the Shiota River, suggesting that that the two masses of hypoxia generated individually were unified because of long-term stratification and massive oxygen consumption by SPM and sediments.

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To clarify influences of large-scale floods on water quality of Tokyo Bay, we performed field measurements on pollutant loads under flood conditions, evaluated the long-term trends of SS, organic materials, and nutrient fluxes, and investigated its relation with DO and nutrients in Tokyo Bay. The large flood event caused by the attack of typhoon no. 0709 was observed to have significantly huge environmental impacts on Tokyo Bay. The comparison between the pollutant loads and DO in Tokyo Bay indicates that subsurface hypoxia at the head of the bay was developed after large flood conditions mainly due to decomposition of organic materials appreciably transported through influent rivers. It is also found that the large flood events influenced the nutrients in the benthic layer.

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Although massive fish death was mostly observed in tidal rivers and mainly caused by hypoxic water mass, there was little information on DO environments in large tidal rivers. To investigate DO environments in tidal rivers with and without massive fish death, we conducted field measurements on hydrodynamics and water quality environments in the Sumidagawa and Arakawa Rivers. In summer, larger intrusion of sea water was found in Sumidagawa River than Arakawa River mainly due to the difference of river discharges, and then DO concentration in the Sumidagawa River was relatively lower than in the Arakawa River. Also found that the intrusion of hypoxic seawater mass and inflows of CSO due to hydrologic events have an important role on reduction of DO concentration in the Sumidagawa River.

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Granulated coal ash was used to restore water environment in a brackish-water lake, Nakaumi, Japan, whose sediment was heavily deteriorated with organic substances. Number of bivalves, Tapes japonica and Scapharca subcrenata, which were important fisheries resources, were significantly recovered 2-3 years after the granulated coal ash covering. Oxydation-reduction potential of the amended sediment with the coal ash was significantly high compared to those with natural sand. Dissolved oxygen concentration in the overlying water was also high at the coal ash amendment site. This means, the sediment oxygen consumption was depressed by covering with the granulated coal ash. From these results, granulated coal ash can be effective to restore water environment and bivalve habitat by amending the organically-enriched sediments.

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The seasonal variations of nitrogen and phosphorus in bottom sediments of tidal flat and shallow water areas in the interior parts of the Ariake Sea were investigated during August, 2007-July, 2008. The supply amount of organic matter to sea bottom and sediment temperature had important effects on the seasonal variations of NH_4-N in porewater. NO_3-N in porewater was significantly influenced by denitrification and NH_4-N in porewater that is substrate of nitrification. The seasonal variations of PO_4-P in porewater were strongly dependent on those of redox environments in bottom sediment. The release rates of NH_4-N and PO_4-P were estimated by the diffusion equation. It was found that bottom sediment was an important supply source of NH_4-N and PO_4-P during summer-autumn.

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In order to clarify formation and disappearance processes of dysoxic water mass which generates near the sea bottom at Kaita Bay, bottom mud properties which contain physical and chemical parameters and water qualities are investigated from summer season to winter season. From this investigation, it is revealed DO near sea bottom decreases when water temperature is low and turbidity increases. Generally, it is known turbidity increases causes formation of dysoxic water mass. It is estimated that the effective density (the difference between water density and suspended matter density) change by water temperature variation triggers the suspended matter motion and causes organic matter to maintain suspended condition.

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Blue tide, upwelling of anoxic water, is a serious water pollution problem in Tokyo Bay. To evaluate each source of anoxic water in navigation channels and dreged trenches, we first proposed a practical method for estimating the amount of sulfide in each water using a measured value of sulfide at the bottom and measured vertical profiles of pH and ORP. We then set an intial condition of sulfide distribution in each water and peformed numerical simulation of upwelling of sulfide using a primitive equation model with nesting. Through the numerical experiments, we can evaluate the contribution of each water to the magnitude and area of the outbreak of blue tide along with its upwelling processes.

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A feasibility study for the evaluation of the Secchi Disk Depth (SDD) by SGLI in Lake Nakaumi which is located in Shimane Prefecture, Japan, was conducted by using the in-situ spectral reflectance data collected in August 2005. As a result, the following conclusions were obtained. (1) The characteristics of spectral reflectance in the lake and their relationship to the band positions of the SGLI sensor were qualitatively understood. (2) Relatively high correlations were obtained between "VN4, VN5, VN6, and VN7" bands of SGLI and SDD. (3)The SDD in the lake can be estimated from the multiple regression method using SGLI four bands (VN4, VN5, VN6, and VN7) with the RMS error of about 0.2 m.

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For effective restoration of enclosed coastal zone under anoxic environment such as Osaka bay, it is necessary to understand characteristics of oxygen consumption by the bottom sediment of ports and harbors. In this study, field measurements of the oxygen consumption rate were carried out during the year in a harbor. Seasonal variations in characteristics of the oxygen consumption by sediment were presented and the formulation of oxygen consumption by bottom sediment was attempted.

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The monitoring program of current and water quality at the mouth of Ise Bay has been conducted since Mar. 2008. The obtained water quality data is compared with datasets of freshwater discharge, meteorological parameters and tide. 1) At the mouth of Ise Bay, the velocity of tidal current is larger than 1m/s at the spring tide. The largest velocity is observed at Irago strait. 2) The residual current in shallow layer is larger at the spring tide rather than at the neap tide.3) Because the shallow water and deep water are mixed by the high speed tidal current at the Irago strait, salinity at the Irago strait is larger than that of the other area.4) The salinity becomes lower several days after the fresh water runoff from rivers. Even if there is little fresh water discharge, salinity becomes higher at the spring tide because the water column is well mixed at the spring tide.

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In some of urban tidal rivers on polluted riverbeds with high loads of nutrients water masses with the minimal concentration of DO near the bottom appear between the river mouths and the upper freshwater areas. Field surveys and numerical analysis are carried out to clarify the mechanism of the appearance in two rivers in Osaka. The 1D numerical benthic model of the type of Wijsman et al.(2002) are applied and represents the observed data well. The sediment is the most polluted in the area with the minimal concentration of DO. The cause of the above minimization is not the wastewater of sewage plants and would be relatively fast sedimentaion rate, the high concentration of sulfide in pore water because of the full supply of sulfate in saline water and the resuspension of the sediment with reducing substances such as sulfide.

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Blue tide events were observed four times in the head of Osaka Bay from July to September, 2005. Strong north wind from the land blew continuously in each event, and the sudden fall of the water temperature of the surface layer and DO of the middle layer were observed at the same time. The upwelling of anoxic water was regarded as the dominant factor of the blue tide events. To discuss these processes, we carried out now cast simulation by using the three-dimensional numerical model by focusing on DO. As a result, the blue tide events and the difference of scales among the events were reproduced. The difference was attributed not only to the strength and weakness of north wind but also to the duration and a condition of the thermal stratification.

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Evaluating the habitat value on tidal flats is important to preserve the coastal environment and to clarify the existence sense of them. With some assessment cases on tidal flat by the organism mass, for example, HSI (Habitat Suitability Index), there are few assessment cases on it by the biodiversity, however. This research carries out the biodiversity assessment and modeling by using a BDI (Biodiversity - Index). The BDI is designed to consider the limiting factor of biodiversity with the relationship between number of species and sediment quality, etc. The results show the BDI model has high reliability about the surmise of all species and the different characteristics of limiting factor with organisms on tidal flats in Ariake Bay.

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Field observations on Zostera japonica habitat and transplanting experiment were conducted in order to obtain scientific knowledge on preservation and restoration of eelgrass beds. The observed seasonal changes in density of Z. japonica were large, and the rhizome biomass had drastically decreased from 0.40g/100cm² to as little as 0.05g/100cm² in a year. The transplanted Z. japonica increased their shoots by 30 times, however, most of the shoots had disappeared in 8 months. The rapid disappearance appears to be due to rise in the sea bed level during the period. It is suggested that sediment inflow from the hinterland must be controlled as well as the possibility of propagation of species be enhanced not only by rhizome extension but by seedling in order to keep Z. japonica community in the site.

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Nutrient fluxes in 3 types of shallow areas (an artificial tidal flat, an artificial Zostera marina bed and a successive area of the tidal flat and the Zostera marina bed) were estimated by investigating water quality under ebb and flow in AGO Bay. In this study, functions of material circulation above 3 types of shallow areas were considered. It is clear that oxygen was consumed by macrofauna in the artificial tidal flat, and oxygen was produced by photosynthesis in the Zostera marina bed. The both areas work as sink for the particulate organic matter and chl. a, and source for dissolved nutrient. Nutrient fluxes in continuous both areas were larger than those in the several artificial tidal flat and Zostera marina bed, because abundance of macrobenthos was strongly linked with the material circulation.

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The objective of this study is to elucidate the burrow structure and to evaluate quantitative physical bioturbation of the dominant species, crab Macrophthalmus japonicus in muddy tidal flat. Burrows consisted mainly of J-shaped structures. Various burrow parameters were strongly correlated with carapace width of M.japonicus. It was estimated that burrows increased the surface area by 5~32% in investigation area. and population of M.japonicus can turn over approximately 3~34% of the upper 20 cm of sediment. These results indicated that burrowing activities of M.japonicus significantly influences the material cycle.

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Relationship between distribution of bacteria and physicochemical characteristics in tidal flat was studied. Sediment samples in Shirakawa river as sandy site and Midorikawa river as muddy site in Kumamoto Prefecture were investigated for the analysis of microbial community and the determination of sediment characteristics such as oxygen-redox potential, organic matter content, and so on. Midorikawa was seemed to be anaerobic and anaerobic bacteria were detected at that site. On the other hand, Shirakawa river was aerobic and aerobic bacteria were detected. Sulfur reducing bacteria, one of the anaerobic bacteria, might be the key group for understanding the relationship between microbial community and physicochemical characteristics in tidal flat.

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In this study, shear wave velocity structures of sandy flats, muddy flats, and subtropical flats were evaluated by means of multi-channel analysis of surface waves (MASW). Spectrum analysis along the cross-shore direction was carried out in order to quantitatively characterize the dominant wavelength for the variations of both shear wave velocity and morphological structures of intertidal flats with various scales and soil types. In the intertidal flats with multi bar-trough structure, dominant wavelengths in a range of 40 to 90 m were obtained, while in the muddy flat or huge-scale homogeneous sandy flat, any dominant wavelength was not obtained. In subtropical intertidal flats, the dominant wavelength was strongly influenced by prominent lime rock rather than the morphological surface variation.

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The movements of the water masses are evaluated by Ra-228/Ra-226 (radioisotope ratio) in the open sea. However, the study on the water's movement in the littoral region based on this ratio is few, because the supply process of Ra-228 is complex. The purposes of this study are explication of the sedimentological characters and the seawater's circulation in the Isahaya bay based on the radium isotope, benthic foraminifers and topography. The erosion and redeposition, that are related with the inflow of the open seawater, are recognized from central to outer area in the southern part of the bay. The radioisotope ratio suggests that the stagnation in the seawater circulation is only present in the front of north drain gate on the dyke in Isahaya reclaimed land.

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In order to grasp return process of brachyuran megalopae to the Amparu Tidal Lagoon, they were collected by using two planktonic nets at the channel connects with the Nagura Bay in Feb. to May, 2007. Many megalopae captured intensively for a short time during the flooding tide before dawn around the new moon periods of Mar. and Apr. Based on the results, the immigration region of megalopa in the sea is estimated, and it seems that they immigrate from the deeper area approximately 500 meters away from the mouth of the lagoon. The settlement distribution of them in the lagoon is examined by using the 2-D Lagrangean chasing simulation. The settlement distribution could be determined largely by not only flow field in this lagoon but also the timing of their return to the lagoon.

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The large-scale coral transplantation with applying asexual reproduction method has been implemented in the shallow lagoon at Kuta Beach in Bali Island of Indonesia. The monitoring and maintenance works after fixing coral fragments were continued for 1.5 years to observe the coral growth and survival conditions. The high survival rate and significant growth of transplanted corals were observed for branching and leaf type coral species which were brought from same coral reef area in comparison with other experiments in Japan. This is mainly caused by different environmental conditions from that in Japan; such as high water temperature with range of 24 to 30 degrees C, no disturbance by storm, inexistence of natural enemy, etc.

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We investigated in detail the performance and mechanics of self-burial activities of bivalves, Japanese Littleneck, from juvenile to adult, by utilizing our new approach encompassing ecology, geophysics and geotechnics. The observed speeds, angles and depths of the self-burial were all governed by the bed surface shear strength irrespective of the types of materials. The increase in the surface shear strength induced the mode shift from the vertical self-burial to inclined and/or partial self-burial, ultimately reaching the non-self-burial state. This self-burial mode shift can be consistently explained by the proposed conceptual model in view of required energy principle. There exists an optimal stage of growth, at which the bivalves can achieve the highest capabilities, below or above which the self-burial capabilities decrease continuously.

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To quantify the natural river's self-purification mechanism, we conducted the field observations in 3 different estuaries - one urban river and two mangrove rivers - at the same period. From comparison of their water qualities, turbidity in urban area (Arakawa river) increased about 10 times immediately after rain. On the other hand, turbidity in mangrove estuaries (Fukido river and Miyara river) didn't change soon and the rate of increase was remarkably smaller than in urban river. TN (Total Nitrogen) and TP (Total Phosphorus) also had same tendencies. It showed that mangrove natural rivers moderate excess outflow of solids and nutrients to coastal area. Adding to it, we compared 2 types of mangrove estuaries with river form and land use and revealed the differences of their moderation effects.

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In this study, a hydrodynamic-primary production coupled model as the water environmental evaluation tool of the Seto Inland Sea has been developed. To verify the model, a simulation was executed. The result showed that the flow field could be reproduced by the model. However concentration fields related with primary production were not well reproduced. The model was applied to the dispersion process of marbled flounder larvae in the Harima nada. The simulation results showed that after 30days floating the larvae mainly distributed around of the Iejima Island, eastward and southward of the Awaji Island and the Bisan seto. Moreover, the larvae that distributed on the Okayama area at the beginning of March came from the spawning ground which located eastward of the Shoudo Island and southwestward of the Awaji Island.

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In order to clarify the primary productivity in disposed coastal area, we measured primary production of phytoplankton by simulated in situ deck incubations in southern part of Kashima-Nada every season from 1995 to 2002. Productivity was high in spring and when river water overflowed in summer. The mean value of the primary production in a site with a bottom depth of 40 m in winter, spring, summer and autumn was estimated at 362, 932, 440, 210 mg-C/m²/day respectively. Production was limited by lack of nutrients (DIN: <1 μM, silicate: <5 μM) or solar radiation (<17.5 MJ/m²/day). Spring bloom occurred from March to May when both nutrients and light condition were good.

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The major objectives of present study are to clarify the properties of heat and temperature environments at the muddy tidal flat in the interior parts of the Araike Sea, and the relationships between these environmental properties and bioturbations such as the burrow constructing or feeding by macrofaunas, in order to obtain the fundamental knowledge for preserving the environment of muddy tidal flat and the rare macrofaunas there. In the present studies, it was shown that there were large differences in the properties of heat balance and soil temperature profiles at the muddy tidal flat in summer and winter. It was also clarified that the air and soil temperature there made affects the bioturbations of macroepifauna strongly, and its active bioturbations reduced the number of the small burrows of macroinfauna.

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Reproductive activity of loggerhead sea turtles can be classified into 3 stages: landing, oviposition, and hatching. The purpose of this study is to investigate the influence of environmental factors such as beach elevation and sand temperature on the reproductive activity of loggerhead turtles nesting on the beach. It was found that the number of landings in the period 2005-2008 was smaller on the beach in front of detached breakwaters than the other areas of beach without breakwaters. The length of tracks with successful nests (oviposition) was significantly larger than the length of tracks with abandoned nesting attempts (oviposition failure). In the hatching stage, sand depth was found to affect incubation temperature.

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ECOHYM (the Ecological Connectivity Hypoxia Model) revealed the daily and annual dynamics of the vertical biochemical-physical oxygen production and consumption rate in the tidal flat quantitatively, based on the validation from two perspectives: (1) the whole estuary, composed of temporal-spatial mutual linkage of the central bay-tidal and benthic-pelagic ecosystems (holistic approach) and (2) each biochemical and physical processes (elemental approach). The benthic oxygen consumption caused by biochemical production during daytime was higher than nighttime due to oxygen production of photosynthesis of benthic algae. This photosynthesis makes the benthic system sometimes an oxygen source for the pelagic system during daytime, although the benthic system is always an oxygen sink during night time.

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It needs to estimate the accurate settling velocity of the suspended organic matter affected by the organic property in order to develop the pelagic-benthic coupled ecosystem model to evaluate coastal religion where organic mud deposits in the bottom. In this study, laboratory experiment was performed to measure the settling velocity of suspended organic matter by particle distribution analyzing for organic matters (flocks). From the results, it was cleared that the effective density decreases with increasing of particle size. Comparing with this result and its organic property, it is understood that the settling velocity is affected by the structural property strongly. And the settling velocity model considering the organic properties was suggested.

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The tidal variations of groundwater salinity and groundwater discharge/infiltration through the riverbed were observed in a tidal estuary. The process of fresh water intrusion and salinity recovery in the riverbed due to flood were analyzed using observed data in relation to the circulation between hyporheic water and wide area groundwater. The groundwater discharge varies with tide in the order of 10^-3cm/s, but the salinity decreases at the surface of the riverbed. The fresh water intrusion to the riverbed during flood depends on groundwater infiltration caused by river water and wide area groundwater, and the fresh water intruded twice deeper than that of tidal intrusion during non-flood period.

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In this paper, field observations were performed in order to clarify the mechanism of groundwater level rising, and variation of groundwater quality under the influence of tidal cycle. Moreover, laboratory experiments using one dimensional infiltration apparatus were conducted to investigate the behavior of salinity in a tidal flat. Observation results suggested that groundwater level rising is occurred by rising of deeper layer of groundwater when river water level is lower than ground level. From laboratory experiments, it was cleared that separation of pore water in free water and bound water is important to consider the behavior of salinity. Ratio of free water increased with increasing of void ratio and decreasing of infiltration velocity. Salinity of bound water varied with infiltration of salt or fresh water.

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A short-time prediction method of sea salt concentration in the atmosphere is developed, considering the transport process in the atmosphere, the emission process from the sea surface, the dry deposition process onto the land and the sea surfaces, and the wet deposition process into water substances. The prediction method is applied to the Sea of Japan, and the numerical results of sea salt concentration are compared with those of an observation obtained at Niitsu in Niigata-shi through January to February, 2008. The characteristics of time-series of the concentration obtained by the model approximately agree with those of observation. The sheltering effect by the mountains at the Sado island characterizes the transport process near Niigata-shi where the concentration of the downwind regions decreases.

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To clarify sediment transport and qualities of sediment in rivers flowing into Tokyo Bay, we performed field measurements and numerical simulation for suspended- and bed-load transports and sediment qualities in the influent rivers. Particle size and ignition loss (IL) of sediment in several influent rivers were found to be similar to those in coastal area. Bed-load transport of coarse and fine sands, which are found in sediments of tidal flat, were larger than the corresponding suspended-load transport, indicating the importance of the bed-load transport for the sediment supply to tidal flat. It is also found that one third of the total sediment yield in the whole basin of Tokyo Bay was trapped in dams located in the basin.

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To consider effective measures using water duct for reducing anoxia in coastal dreaged trenches, we first developed a water quality model including dissolved oxygen and sufide processes copuled with hydrodynamic model using MIKE3 and ECO Lab (DHI). The model was applied to reproduce water quality processes in dredged trenches with one-way nesting approach and verified through comparison with measured data. Peforming numerical experiments installing water duct and transporting oxygen rich water, we showed that transport of surface water with less dense is effective and more practical for the present purpose.

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Nutrients are released from the contaminated sediments on the sea bottom. In order to improve the sediment quality, sand capping techniques were utilized at several coastal seas. However, the technique is worry about the effectiveness due to newly deposited sediments on sea bottom. This paper describes the lasting of sand capping techniques on nutrient release reduction from contaminated sediments by field experiments at MM21 district in Yokohama Port. From the study, it is found that the lasting of sand capping techniques on nutrient release reduction is still remained. But the effect of sand capping technique is decreasing due to newly deposited contaminated sediments on clean sand capping sands.

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In this study,we discuss about an evaluation method of restoring nature planning involving a reformation of breakwater. To promote a exchange of seawater and to improve a habitat environment for coral community, reforming breakwater is examined. As an increase of permeability of a breakwater decreases an efficiency of absorbing waves, the relationships between the improvement work to promote a exchange of seawater and the disaster prevention work such as a breakwater make trade-off problem. In this paper, we examined multiple plans of reforming breakwater by considering the risk of loss about that problem. The optimum plan to remove a part of breakwater was proposed.

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Though a sand banking method is known to be effective to improve an environment of bottom sediment, there is no common method of construction or monitoring investigation. Duration of effect is also not clear. In this study, we verified the duration of effect of sand banking method based on monitoring investigation for 17 years in Tsuda Bay. As a result, it became clear that the effect lasted 17 years on improvement of sediment, elution of phosphorus, and a habitat of bottom fish.

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Biofouling on a steel slag hydrated matrix using steel-making slag as the aggregate and ground granulated blast-furnace slag as the main binder was investigated in enclosed coastal areas, and was compared with that on concrete and a natural rocky shore. The steel slag hydrated matrix tended to display larger microalgal density and diversity than concrete from the initial period at the start of the test, confirming that microalgae readily grow on the steel slag-based material. At a seawall where large-scale works were executed, the biofouling on the steel slag hydrated matrix was equal or superior to that on the natural rocky shore. Based on these results, the steel slag hydrated matrix was judged to be excellent in biofouling performance.

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As a part of MLIT's efforts for "Restoration and construction of tidal flats by reused dredged soil", an experimental tidal flat had been created in Kyushu sea area for developing the utility of the dredged soil. In order to evaluate and verify the improvement effect on the environment, we carried out monitoring research on the habitat environment, habitat situation and the condition of the sea area at 3 sites - Port of Miike, Port of Ooura, and Port of Nakatsu. As a result, environment improvement in the sea bottom was observed in the artificial tidal flat with reused dredged soil, and it was confirmed that such artificial environment served as a suitable habitat for marketable species and the diversity of benthos.

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Tidal flats in Ariake Bay were reclaimed from pre-Edo era to the post-WWII food shortage period for the main purpose of increasing farmland. In the process, high banks were constructed to protect farmland existing around the supratidal zone (shoreline). This, however, has led to the loss of waterfront or coastlines, as well as the ecosystem innate to the tidal flats, including the habitat of benthos and saltwater plants. This is thought to be one of the factors of the environmental deterioration of Ariake Bay. In this study, the prediction method of the benthos species and the biomass when the shoreline was artificially recovered was examined.

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The purpose of this study is to evaluate effect of hypoxic water and blue tide on macrobenthos in artificial tidal flat, Omaehama in inner part of Osaka bay. Hypoxic water influences on macrobenthos to survive under to 1m water depth. In addition, it was revealed that bule tide influences on the amount of filtered water by Ruditapes philippinarum in DL±0m water depth. Blue tide decreased individual of R. philippinarum and the amount of filtered water by them. It is found that the creating artificial tidal flat enhances the number of R. philippinarum and filtaration, but occurrence of blue tide causes disappearance of purification function. These result indicated that it is necessary to consider the method for mitigation of blue tide impact when creating artificial tidal flat.

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This study is aimed for establishment of the breeding technique by the zoogamy of Acropora tumida. The natural restoration works for coral communities has been carried out in the Takegashima underwater park located in Southeast Shikoku. A breeding by the zoogamy is effective for the restoration of the coral. Therefore we conducted field works about the growth process of this coral from eggs to juveniles. As a result of investigation of three years, we obtained some important ecological characteristics of this coral, such that laying eggs occurs about on July 3 in lunar calendar.

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Field surveys and indoor experiments were conducted to prevent the outbreak of green tide by Ulva pertusa at Osaka Nanko Bird Sanctuary. Reduction of biomass of Ulva pertusa was observed at stations where exposure rate to the air was from 30 to 40%. In addition, the exposure rate of 30 to 40% to the air showed no negative impacts on the benthic microalgae and macro-benthic animals. Laboratory experiments revealed that photosynthesis activity of Ulva pertusa decreased when exposed to air for 4 to 7 hours at 25- 35℃. Salinity decrease from 30 to 25 or 20 psu in accompanied with exposure to the air drastically inhibited the photosynthesis of this species. These results suggest the possibility of controlling a green tide of Ulva pertusa without any damage to benthic microalgae and macro-benthic animals by a combination of ground level and low salinity.

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The paper describes an interspecific comparison of burrowing capabilities of benthic fauna in tidal flats. By utilizing our new approach in Ecological Geotehcnics, we simulated and varied surface shear strengths of bed materials, to which we observed the responses of six species of invertebrates that belong to Arthropoda, Mollusca, and Annelida. The results demonstrate that for each of the burrowing activities there exist optimal, transitional and critical surface shear strengths, which are found to differ considerably between species, body sizes and weights. We have constructed a chart by which to examine such difference in the burrowing capabilities in an integrated manner in light of the associated geophysical environments in the field. This chart provides fresh important insights into natural selection of habitats of benthic fauna in tidal flats.

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The behaviour and characteristics of suspended solids were examined using a sediment trap method at Hinuma Lake, a shallow estuarine lake, from November of 2007 to January of 2008. In a vertically well-mixed period, phytoplankton accounted for 17% in suspended solids. Hence, particulate organic carbon, nitrogen and phosphorus in suspended solids derived largely from phytoplankton. In contrast, only 4-6% of phytoplankton occupied in suspended solid in a stratification period. Fluid muds, resuspended due to wind, were likely to be a contributor for particulate organic carbon in suspended solids.

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The sedimentation environment characteristics and distribution characteristics of benthos were studied based on the past investigation data of bottom material, water quality, benthos, tidal current and investigation data of fluid mud layer in the inner area of the Ariake Sea. It is suggested that the change of kind number of benthos was corresponds to the degree of bottom environment deterioration shown in mud content, ignition loss and AVS (acid volatile sulfides). By the geographic distribution of layer thickness, it is suggested that fluid mud layer was precipitated the west slopes of submarine channels and the east slopes of submarine sandbars where there were located at the outside of tidal current.

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An optical environment under the sea is important for designing environmental restoration. Irradiance under the sea is affected by SS(Suspended Substance) which is variable spatially and temporally, so it is not so easy to understand the optical environment. Therefore, it is important to investigate actual phenomena in the field. This study describes a decay of incident rays of sunlight with water depth based on the observation in the head of Osaka Bay. The decay of incident rays defined as the absorption coefficient, k, was considered. In the result, monthly averaged value of k was between 0.94m^-1 and 1.15m^-1 in the summer and between 0.46 m^-1 and 0.59 m^-1 in the winter. Moreover, a compensation depth or a compensation point based on k was examined and it suggested that the photon flux density was insufficient for seaweed (or seagrass) on the sea bottom in the head of Osaka Bay.

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Large volume of mussels attaches on the coastal structure in eutrophic area. The dropped and died mussels accelerate the depression of dissolved oxygen in the bottom layer. This study revealed the relationship between fluctuation of salinity and temperature and their attaching activity on the wall. Result of our investigation at Amagasaki Harbor in Osaka Bay showed that the mass of mussels dropped out at the bottom after the salinity and temperature had extensively changed. It was also observed in Komatsushima Harbor that the salinity and temperature jumps initiated the dropout of the mussel. From laboratory experiments in different environmental conditions; salinity and temperature, we cleared the ecological cycle of the mussels in which the changes in salinity and temperature mainly influenced their activities.

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