Development of Ecosystem Model for Optimum Design of Artificial Lagoon

本研究旨在建立适用于沿海封闭海域环境修复的生态技术之一--人工泻湖优化设计的生态系统模型。研究方法包括在大阪湾南部仁古公园内海进行实地调查、现场实验获取生物过程参数以及基于野外调查和现场实验结果建立生态系统模型。野外调查结果表明，海藻具有较大的固碳、固氮和供氧功能，而枯萎的海藻则是沉积有机质的来源。现场实验结果表明，底泥耗氧速率主要取决于水温，海参取食海藻是有选择的。利用所建立的生态系统模型进行的数值实验结果表明，由于沉积有机质的积累，人工泻湖的碳和养分的固定效果逐年下降，而由于光照强度的降低抑制了海藻的生长，固定效率随着人工泻湖水深的降低而增加。

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.