Conservation Biological Study Based on Multistability and Material's Circulation in Eutrophicated Lake Ecosystems

在一个由藻类（m.e uluginosa）、鞭毛虫（m.g utula）和少量细菌（P.putida等）组成的微观环境中，研究了模拟湖泊生态系统的种群动态和稳定性。古特假单胞菌对铜绿假单胞菌的捕食效果与营养物浓度呈权衡关系；随着营养浓度的增加，食品（铜绿假单胞菌）的品质提高，从而提高了guttula的生长速度。然而，高营养条件提高了铜绿假单胞菌的光合活性，提高了溶液的pH，从而降低了假单胞菌的生长速度。在中等营养条件下，铜绿假单胞菌的灭绝或存活取决于古假单胞菌的初始种群，表明模型系统具有双稳定性。利用微傅里叶变换红外光谱（FTIR）研究了铜绿假单胞菌细胞中生物分子组成随营养物质浓度的变化。在高营养条件下，糖原和脂质含量在对数生长期增加。这可能表明绿脓杆菌在富营养化条件下能有效地吸收和利用营养物质。建立了考虑水温升高的湖泊生态系统数学模型。模型分析表明，水温存在一个临界值，夏季水温超过临界值就会发生藻华，表明湖泊生态系统发生了政权转移。同时指出，大型植物对抑制藻华具有显著作用，湖泊生态系统管理需要考虑湖泊生态系统不确定性的反馈控制。

Population dynamics and stability in a model lake ecosystem have been studied by using a microcosm consisting of algae (M.aeruginosa), flagellate (M.guttula), and few bacteria (P.putida, and so on). The predatory effect of M.guttula on M.aeruginosa exhibited a trade-off with respect to the concentration of nutrient; The quality of food (M.aeruginosa) was increased with increasing the nutrient concentration, thus the growth rate of M.guttula was increased. However, high nutrient conditions increased the photosynthetic activity of M.aeruginosa, which increased the pH of the solution, and thus the growth rate of M.guttula was decreased. Under the conditions of intermediate nutrient conditions, M.aeruginosa was extinct or survived depending on the initial population of M.guttula, suggesting bistability in the model system.A micro-Fourier transform infrared (FTIR) spectroscopy was used to study changes in cell compositions of bio-molecules in M.aeruginosa depending on the nutrient concentrations. The amounts of glycogen and lipid have been found to increase in the logarithmic growing phase under the high nutrient conditions. This may suggest that M.aeruginosa absorbs and uses nutrients effectively under eutrophicated conditions.A new mathematical model of a lake ecosystem has been constructed taking into account of increase in water temperature. Analyses of the model shows that there exists a critical value of water temperature, and that algal bloom occurs if water temperature exceeds the value in summer time, suggesting regime shift in lake ecosystems. It was also pointed out that macrophytes have significant effects on suppressing algal blooms, and that management of lake ecosystems needs feed back control by taking into account of uncertainty of lake ecosystems.