Research on Accumulation Mechanism of Freshwater Red Tide in a Dam Reservoir

对寿人集水库库首秋季多甲藻分布型和现存量的日变化进行了观测。结果表明，该虫的分布有3种模式：（a）白天在水面聚集;（B）夜间向下层和溪流扩散;（c）在倾伏点附近向下层扩散。多甲藻的现存量以相似的生长速率逐日增加。由于生物体是以逆流的方式迁移的，因此生物量在一天中以24小时为周期发生周期性变化。这些结果表明，该赤潮在生长、输入和输出的平衡中发展和消散。II.在不同温度和光照条件下，测定了多甲藻的游动速度矢量。通过对数据的分析，建立了多甲藻群落垂直游动速度的数学模型。此外，利用水池和假定水库水头的数学模型，研究了赤潮的积累和扩散过程。建立了模拟淡水赤潮生物量日变化的数学模型。它使用流体动力学模型预测输入和输出，使用垂直游泳模型预测垂直分布，使用生态模型预测生长。该模型成功地模拟了寿人集水库库首多甲藻的时空分布。这些结果表明，淡水赤潮的积累机制可以从工程角度进行处理。

I.The diurnal change of distribution patterns and standing crop of Peridinium were observed at the head of Shourenji Dam Reservoir in autumn. There were three distribution patterns ; (a) accumulating at the surface in the day time ; (b) dispersing to lower layr and stream in the night ; (c) dispersing lower layr near the plunging point. The standing crop of Peridinium increased at similar rate of growth day by day. Since organisms were transported by the counter flow, The biomass periodically varied at 24 hours cycle in a day. These results show that the red tide develops and dissipates in the balance of growth, import and export.II.Swimming velocity vectors of Peridinium were measured under various temperature and light intensity conditions. Analyzing obtained data sets, we constructed a mathematical model that predicted the vertical swimming velocity of Peridinium community. Furthermore, using the water tank and the mathematical model that assuming the head of a water reservoir, we examined the accumulation and dispersion processes of red tide. The mathematical model including the vertical swimming responses could simulate the diurnal change of biomass.III.We developed the mathematical model that simulate the accumulation mechanism of freshwater red tide. It predicts the import and export using the fluid dynamics model, the vertical distribution using the vertical swimming model, and the growth using the ecological model. This model successfully simulated the temporal and spatial distribution of Peridinium at the head of Shourenji Dam Reservoir. These results suggested that accumulation mechanism of freshwater red tide could be treat in the term of engineering.