The formation of oxygen water depleted mass during summer is a main environmental issue of the Mikawa Bay. Sinking fluxes of plankton and detritus greatly influence on the generation process of oxygen depleted water mass. Because the sinking organic matter is decomposed by bacteria using oxygen. The terrestrial loading of nutrients and organic substance had increased in Mikawa Bay until about 1980. and also intensive reclamations were carried out in shallow sea area of Mikawa Bay in 1970s. Therefore we have thought that the formation of the oxygen depleted water mass in Mikawa Bay could be related to an increase of the loading and the land reclamation. In this study, we attempt to determine which is the main process to form the oxygen depleted water mass, by using a numerical ecosystem model. The model run covered from 1961 to 1990. The model results show increased sinking flux of particulate organic matter that related to the oxygen consumption in the sediment in the first half of 1970s compared to early 1960's. It exceeded 500 mgC/mVday in the latter half of 70s. and this level was maintained afterwards, even though the nutrient loading from terrestrial origin decreases in the latter half of 80's. The reclamation of Mikawa ports starts in 70's. and then the amount of the resource the shellfish decreased. The model results show the negative correlation between the shellfish resource and total area of oxygen depleted water mass exists. Therefore, we can conclude that a decrease
of the shellfish due to the reclamation greatly influenced on formation of the oxygen depleted water mass.
In order to identify phytoplankton taxonomic compositions by optical characteristics, we examined a relationship between the pigment composition and the excitation fluorescence spectrum using purely cultured species (Cyanophyceae. Bacillariophyceae.
Raphydophyceae. Chlorophyceae, Dinophyceae). Excitation spectra and phytoplankton pigments were measured by a
spectrofluorometer and a RP-HPLC with a phtodiode array detector. Cyanophyceae showed a characteristic spectrum caused by phycobili-protein pigments (PB). The fluorescent intensity was extremely high from 545nm to 600 nm. and it varied depending on the ratio of phycocyanin and phycoerythrin. Bacillariophyceae. Raphydophyceae and Dinophyceae had a broad peak at around 530 nm. which reflected the existence of light-harvesting-carotenoids (LHCs) in chloroplast. On the other hand. Chlorophyceae did not have any peak at the longer wavelength region than 500 nm. because there is no PB and LHCs which absorbs light at the wavelength region. From these excitation fluorescent features, these five classes could be characterized to three groups; Cyanophyceae. Chlorophyceae. and carotenoid-contained class (e.g. Bacillariophyta, Raphydophyceae and Dinophyta). Finally, we resulted that three fluorescent intensity ratios: [f(490)/f (530)1. I f (545)/f (440)1 and [f (545)/f (440) 1. enabled the identification of the three groups. Our results showed that the fluorescence-excitation-spectra measurement was helpful to classify phytoplankton-taxa based on the pigments composition. This information will be appreciable to develop an in-situ excitation fluorometer for automatic identification of phytoplankton groups.
Environmental transfer model for radionuclides in Lake Obuchi. a brackish lake neighboring the nuclear spent-fuel reprocessing plant. Rokkasho-Village. Japan, has been also developed until 2005. The Lake Obuchi model consists of a water current model and an ecosystem model including lower trophic level organisms. Although the model successfully described background 3H concentration in lake water, the depth profile of l37Cs in sediment was not well simulated. To improve the simulation, the model should include the watershed of Lake Obuchi as a source supplying 137Cs and other radionuclides. Therefore, a watershed model of Lake Obuchi and an ecosystem model includingalso higher trophic level organisms are planed to be developed for describing the behavior of radionuclides in aquatic system in Rokkasho. In fiscal year 2006. we selected the SWAT(Soil and Water Assessment Tool) model, which was originally developed by USDA Agricultural Research Service, as the best one for our purpose among various watershed models.
Oil Spill is one of the most critical issues for the marine environment. The most important thing to minimize the influence is how to find spilled oil area when it occurred. Satellite remote sensing is suitable for use of the disaster surveillance because a periodically wide area can be observed. EspeciallySAR (Synthetic Aperture Radar) can observe the object regardless of day and night, without being influenced by clouds. It is desirable to perform spilled oil are extraction from the SAR imagery automatically, although a visual decipherment technique is main under the present circumstances. In order to solve this problem, the possibility of automatic extraction of spilled oil area in the multi-resolution Wavelet analysis was examined. By applying the multi-resolution Wavelet analysis to SAR imagery, we found the possibility of the detection of spilled oil area. It is possible for automatic recognition of spilled oil area without human interpretation if this technique is established.
We carried out sensitivity analysis using ECOS3D model (Nakata ci al.. 2004) in order to investigate to influence what on the spatial distribution of nutrients (NO3, PO4). Net Primary Production (NPP). export (lux and CO2, fugacity (fO2) in the world ocean by changing parameter of phyloplankton of half saturation constants for PO4 and NO3 uptake, maximum cell-quota capacity (P-quota and N-quota). C/P and C/N ratio and minimum growth temperature. It revealed the possibility that small size phyloplankton may hardly to have cell-quota by comparing the model result with the observation data(WOA01) on nutrients. The model result on fCO2. NPP and export flux also showed the possibility that the activity of phyloplankton in high latitude region may influence on CO2 absorption assessment in the world ocean.
Parts like human eyes are necessary for underwater vehicle to investigate and work under high pressure. Pressure-resistant optical windows are used for underwater cameras equipped in a Remotely Operated Vehicle (ROV) and Autonomous Underwater Vehicle(AUV) in deep sea. A glass dome type lens is often used for this purpose. However, this lens has a great problem when it broke; an internal camera was flooded and broken. A conical trapezoid lens called, below viewport, makes up the fault. Acrylic glass view ports were mainly developed, and the standard for design of acrylic glass viewports are established through a detailed experiments. However, there are needs to get clear images of the deep sea with a high vision camera. For this needs. Borosilicate glass (BK7) has better quality than acrylic glass on the physical characteristics. There were few report about BK7 viewports especially in pressure proof test Mere we carried out high pressure tests for the BK7 viewport, and measured strains. From the test result, we derived a thickness of the most suitable BK7 viewport, and suggested an empirical formula for the optical design of this viewport thickness.
We developed a numerical model of ecosystem dynamics to explore how the behavior of plankton influences the coastal ecosystems with a system dynamics tool, which is named MSFTM (Marine Stoichiometric. Functional Type Model). This model takes stoichiometry of nutrients and plankton functional type into account so that it can handle elemental cycle and biological processes. MSFTM is mainly composed of nutrients (DIN. DIP. DSi). phytoplankton. zooplankton and detritus. Two types of algal functional type, namely Diatom and Flagellates were considered. The Diatom takes DSi as well as DIN. DIP and plays important role on biological pumping. The Flagellates, which generically represents non-diatom (non-seliceous) algae and small contribution to biological pumping. We tested the performance of MSFTM and showed how different behaviors of two algae influence the system in terms of siliceous (therefore fast sinking) or non-siliceous (therefore slow sinking).These resultssuggest that the numerical model with system dynamics could contribute to efficient analysis for pelagic ecosystem by integrating various biological processes.
It is necessary to develop technologies to reduce anthropogenic C02 emission into the atmosphere to control global warming. The ocean sequestration technology is one of the promising measures, considering a large potential capacity of CO2 sequestration of the ocean. The RITE has advanced the project of ” Study of Environmental Assessment for CO2 Ocean Sequestration for Mitigation of Climate Change” for the ocean sequestration technology using the Moving Ship method by the subsidy of the Ministry of Economy, Trade and Industry. In the ocean sequestration project, the technology assessment of the CO2 ocean sequestration ability, the development of the environmental assessment technology, and the development of the CO2 dilution technology have been conducted as an individual element technology. As a result, a lot of outcomes have been steadily accumulated, such as the CO2 sequestration capacity of
the ocean and economical benefit and risk by the ocean sequestration, development of a CO2 acute influence model for marine organisms, development of a basic model for deep sea ecosystem, and development of CO2 dilution and diffusion models, and grasp of design condition of CO2 discharge nozzle. In this report, the results of the first half of the project's Phase 2 were chiefly explained. First, the concept of ”CO2 sequestration technology by the Moving Ship method” was described. Next, the some results of element technologies were explained, such as dissolution process of liquid CO2. diffusion of dissolved CO2 in ocean, and influence on marine organisms by dissolved CO2. Finally, the result of ”Case study of 50 million-ton/year ocean sequestration in a selected site” was introduced based on the knowledge and findings obtained in this research project continuing for more than ten years.
In order to evaluate the impact of sequestration of CO, in the ocean to the deep-sea benthic community, in situ experiment using a free fall type of benthic chamber system was carried out in Kumano trough at a depth of 2,000 m. The exposure concentrations of CO2 averaged 5.000 μatm and 2.000 μatm for the two exposure chambers and an intact chamber as a control has prepared. The number of foraminifera declined in the chamber of 5.000 μatm pCO2 compared with the control. On the other hand, biomass of each taxa in the chamber of 2.000 μatm pCO2 was not changed. These results suggest that the threshold concentration of the acute effect of C02 for the benthic community is recognized between 2.000 and 5000 μatm.
To evaluate whether chronic impacts on biota are caused by 50 Mton CO2 injection per year into the ocean, we simulated transport and dilution of injected CO2 using an offline oceanic general circulation model (OGCM) with a horizontal resolution of 0.1 by 0.1 degrees. Carbon dioxide is continuously injected for 30 years into a site with 1 degree in longitude and 3 degrees in latitude. Most of the CO2 dissolved water is transported in the longitudinal direction. In addition, inter-spatial correlation of the CO2 concentration is relatively higher in the longitudinal direction than in the latitudinal direction. Therefore, a site with large latitudinal width is effective to decrease C02 concentration in order to reduce/avoid biological impacts. CO2 concentration increases first several to 10 years, but shows signs of levelling off after the initial increase. As the simulated maximum CO2 concentration is 80 % of the ” predicted no effect concentration” (PNEC) which is an index to estimate concentration causing no effects on biota, we conclude that 50 Mton CO2 injection per year causes no chronic impacts.
Biological effects on the case study of ocean carbon sequestration in the subtropical ocean were investigated. Among various organisms living in the ocean, copepods is the most dominant zooplanklon in the ocean from the surface to the deep sea. therefore we use copepods as a model organisms of the biological effects. We considered the effect on 3 viewpoints; direct collision, acute and chronic mortality.
One is the direct collision of each animal with liquid CO2 droplets. Although there were the rising liquid CO2 droplets in the sequestration zone, the mortality rate of zooplankton by the collision with liquid CO2 droplets was supposed to be small, because zooplankton individuals was expected to move on the stream neighbor of liquid CO2, droplet and to avoid the striking. Second point is the acute lethality resulted from the exposure with the dense concentration of CO2 during the dissolution of liquid CO2. From the acute experiments using the pelagic copepods. no observed effect concentration (NOEC) was estimated as 5.000 μatm.
The last point is a long-term effect of the diffused CO2 in the ocean. The predicted non-observable effect concentration (PNEC) .
which no organisms in the ecosystem were affected with the target chemicals, was proposed as a threshold of the long-term effects. PNEC of sequestrated CO2 was estimated as 500 μatm calculated with NOEC and the assessment factor. The Assessment factor in the case study was selected as 10. because the NOEC about the reproductive effect of copepods was obtained. Although the sufficient biological data does not obtained, we can overlook the approach of the biological assessment through the case study. Further accumulation of biological data, e. g. various species or chronic data, is required.