The global carbon recycling system related with soil ecology is not well understood, and the plankton ecosystem variation in the ocean surface with the CO₂ dissolution should be studied in relation to its effect on the fishery resource. Also, the risk assessment on the ecosystem will be important for the CO₂ sequestration. And, it is another important thing that the human being social-life should be made depend on the solar energy, which would be related to the ecoengineering. These subjects should be totally discussed from the view point of the eco-engineering to minimize the uncertainty on the global warming. “Withdraw from carbon society” is an important keyword for the post Kyoto Protocol, but it is preferable to think a wider system of global environment remediation with the core of “withdraw from carbon society.” In this sense, the role of the Society of Eco-engineering in the global environment remediation is considered to become more important from now.

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Establishment of an experimental system composed of plants, animals and humans, in which materials are circulated in a closed loop, is underway using the Closed Ecology Experiment Facilities (CEEF), for investigation of carbon dynamics. The plant cultivation system takes roles of supplying food, oxygen and clean water to, and scrubbing carbon dioxide from, humans and animals in the experimental system. A hydro-culture technique is used for the plant culture system. It is necessary to circulate nutrient solution in the plant cultivation system in order to circulate water in the CEEF. To obtain data on carbon transfer using the CEEF, it is necessary to establish a steady plant cultivation system. In the system, water transpired from the plants are collected as condensate, and it is reused for replenishment of water in each plant cultivation bed. In order to circulate water, not only transpired water but also waste nutrient solution need to be regenerated and reused. Main crops in the plant cultivation system include rice, soybean and peanut. Some elements such as copper and zinc were accumulated, but total organic carbon (TOC) did not increase in the nutrient solution, when the nutrient solution was circulated. This study compared the soybean yield cultivated using the circulated nutrient solution (circulating system) with that cultivated using newly produced solution (non-circulating system). Result of this study showed that circulation of nutrient solution did not decrease soybean production compared to that without circulation of nutrient solution. This research was performed under contract with the Aomori Prefectural Government, Japan.

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Freshwater is essential to life in a closed habitation. An enormous amount of freshwater is used for drinking, daily use and hydroponics and recycled. In order to control the microbiological quality of the water used in a closed habitation system, it is important to rapidly obtain accurate information of the numbers and types of organisms. In this study, we applied the fluorescent vital staining (double staining with 6-carboxyfluorescein diacetate (CFDA) and 4',6-diamidino-2-phenyl indole (DAPI)) and microcolony method to freshwater used in the Closed Ecology Experiment Facilities (CEEF) and determined the abundance and physiological activity of the bacteria in this closed habitation system. Bacterial population dynamics were analyzed by denaturing gradient gel electrophoresis (DGGE) with the PCR-amplified 16S rRNA gene of bacteria in water used in closed habitation system. Bacterial numbers in the purified water in the tank, tap water and shower of this system were 10³ to 10⁵ cells/mL during the experimental period. Many of the cells had esterase- and/or growth activities and the proportion of bacteria with the growth activities gradually increased. In the water used for hydroponics, the bacterial number was 10⁵ to 10⁶ cells/mL. The bacterial community structure was steady in purified water in the tank, but the dominant bacteria in the hydroponic solution in the tank were significantly changed. These techniques would provide early warning of an impending problem and might be applicable to rapid and accurate microbial monitoring of a closed habitation.

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In this paper, the relationship between system diversity and its stability was discussed using a mathematical model of a microcosm reported in the first report. To examine this relationship, behavior of the system for changing number of species and maximum growth rate coefficients of microorganisms was observed. Maximum growth rate coefficients in the model were adjusted through the activity indices for cell division (energy for multiplication). The following aspects were analyzed in simulation results: (1) spatial habitat segregation for two kinds of decomposers was observed, and when they competed spatially, the system became thermodynamically unstable; (2) coexistence through differentiation of characteristics of organisms was quantitatively determined; and (3) the stability of the system was observed by changing the topology of the food web and strength of its links. These results provided information about invasion of an existing ecosystem by a new species.

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In this study, chlorophyll fluorescence imaging of the maximal yield in the dark was applied to estimation of cell concentration of Amphidinium sp. As the result, a linear relationship was observed between chlorophyll fluorescence intensity and cell concentration. It was revealed that the method enabled rapid measurement of cell concentration without effect of chlorophyll fluorescence induction. To investigate the effect of light qualities during the culture on photosynthetic activities of Amphidinium sp., changes in Φ_PSII of the algae cultivated under red, blue and red+blue lights were compared. As the result, the Φ_PSII of algae cultivated under red+blue light was higher than that under blue light. It was implied that the light quality affected the efficiency of the photosynthetic electron transport. Meanwhile, the Φ_PSII of algae cultivated under red light was similar to that under red+blue light in spite of its low growth rate. It was implied that the heat dissipation of Amphidinium sp. cultivated under red light did not increase because their low chlorophyll concentration led to low light absorbance.

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