水动力条件下藻类动态模拟

Simulation study on algal dynamics under different hydrodynamic conditions

藻类动态变化是其内部生理特征和外部驱动因素综合作用的结果.除了藻类自身生理因素及光、温度、营养盐等因素,水动力作用使底泥发生再悬浮所造成的营养盐的内源释放对藻类的影响也非常重要.1999年5月8日～6月24日在太湖湖泊生态系统研究站大型生态实验槽中进行了模拟水动力条件下的太湖藻类动态实验,并应用国外先进的PHREEQC软件从生物化学和生态动力学角度建立了藻类生态动力学模型.模型不仅考虑了氮循环及磷循环,还考虑了水动力条件引起的内源释放问题,根据2003年4月26～4月30日在河海大学环形水槽所做的底泥释放实验结果建立了水流和各形态氮磷营养盐释放的定量化关系.由于目前太湖的野外监测资料存在较明显的时空不一致性,模型参数率定的精度受到了较大影响.从室内模拟实验出发,通过对生态槽实验结果的模拟,确定和验证了模型的各参数值,计算结果显示模拟值能较好地拟合实验测量值,表明所建藻类生态动力学模型能较好地描述藻类及各种营养盐的动态变化,这对揭示藻类'水华'暴发机理有一定的意义.

Algae growth is affected by both their physiological characteristics and the external driving factors, including light, temperature and nutrients. The nutrients released from sediment resuspension under hydrodynamic forces, impose significant effects on algae growth. In this study, an experiment of Taihu algal dynamics under different simulated hydrodynamic conditions was carried out in an ecologic tank. The experiment was conducted using water and sediments collected from Taihu under three different hydrodynamic conditions： static, slow water flow, and fast water flow. Based on the experimental data, an algal growth model was developed using the PHREEQC simulating package and incorporating observed biochemical and ecological kinetics. Quantitative relations between the releases of nitrogen/phosphorus nutrients and the water flow velocity were incorporated in the model based on the results from laboratory experiments of nutrient release from sediments in an annular tank. Detailed calibration and verification of the model parameters were carried out based on the experimental results. The calculated values fitted well with the data, suggesting that the developed model represents the dynamic growth of algae reasonably well. This model may be used to study the mechanisms of algae bloom in Taihu. Key words ：hydrodynamics ; Taihu algae growth ; PHREEQC; algal growth model ; parameter estimation