流溪河水库水动力学对营养盐和浮游植物分布的影响

流溪河水库2001年年降雨量2250mm，其中79％来自4月至9月的丰水期。入库流量变幅4．25～414．00m^3／s，近60％的入库水量流来自吕田河。流域营养盐输送量取决于流域降雨径流强度，吕田河高于玉溪河。由于营养盐被泥沙吸附沉积，丰水期湖泊区营养盐浓度明显低于河流区。浮游植物密度为17～1245cells／ml，以硅藻为主要优势种群。硅藻密度分布与水流流速和透明度的相关程度明显高于与营养盐和温度的相关程度。在丰水期，由于受水流和透明度的强烈控制，尽管营养盐供应比较充足，硅藻密度处于比较低的水平。丰水期硅藻密度稍低于枯水期，河流区明显低于大坝处。浮游植物香农-威纳多样性指数为0．97～2．75。受水库水动力学(水位波动等因素)的影响，最大浮游植物多样性出现于水位波动比较大的8月份，最小值则出现于水位波动最小的6月份。

Effect of hydrodynamics on nutrient and phytoplankton distribu-tion in Liuxihe Reservoir

Effect of hydrodynamics on nutrient and phytoplankton distribution was studied in 2001 in a tropical reservoir, Liuxihe Reservoir (South China). The annual precipitation was 2250 mm and about 79% was contributed by the flood season (from April to September). Reservoir inflow varied from 4.25 to 414 00 m 3/s, and was primarily from the Lutian River and Yuxi River. The Lutian River contributed about 60% of the reservoir inflow. During the raining season, high suspended materials were transported into the reservoir by overland runoff. Then, high nutrient concentration and low secchi disk depth was found. Nutrient input was higher in the flood season than in the dry season and depended mostly on the intensity of rainfall. Nutrient input was higher from the large catchment area Lutian River than that from the Yuxi River. Phytoplankton density was between 17 and 1245 cells/ml and contributed mostly by diatom. Diatom abundances showed more significant relationships with inflow than with nutrient and temperature. Because of short residence time, diatom abundance was maintained at relatively low level, although the nutrient supply was relatively rich in the flood season. Phytoplankton Shannon Wiener diversity index varied between 0 97 and 2 75, with the maximum found in August. It was likely that hydrodynamics such as water level fluctuation acted as a disturbing factor and maintained high phytoplankton diversity in the reservoir.