Development of Ecosystem Model for Optimum Design of Artificial Lagoon

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The aim of this research is to develop an ecosystem model for optimum design of an artificial lagoon, one of the eco-technologies, which is applicable to environmental restoration of enclosed coastal seas. The research approach consists of field surveys at Inner Sea of Rinku Park in southern part of Osaka Bay, on-site experiments for getting biological process parameters, and ecosystem modeling based on the results of the field surveys and on-site experiments. The results of field surveys showed that seaweeds have large carbon and nutrient fixation functions and oxygen supply functions, but the withering seaweeds become origins of sedimentary organic matter. The results of on-site experiments demonstrated that oxygen consumption rate at sediment mainly depends on the water temperature, and sea cucumbers feed seaweeds by choice. The results of numerical experiments using the developed ecosystem model suggested that the carbon and nutrient fixation effects of the artificial lagoon decreases year by year because of the accumulation of the sedimentary organic matter, and the fixation efficiency increases with decreasing the water depth of the artificial lagoon since the reduction of the light intensity inhibits the growth of seaweeds.