筑坝河流水动力条件对浮游植物动态变化的影响

河流筑坝后水动力条件发生改变,影响了浮游植物的动态变化,目前对这一过程的研究相对较少。为此,本研究对乌江河流-水库体系浮游植物和流速及相关环境因子进行了季度调查。研究区域水体平均流速为032 m/s,变化范围为001～132 m/s;浮游植物中硅藻、蓝藻、甲藻对水体流速变化最敏感:在流速小于005 m/s时,蓝藻与硅藻占比最大,甲藻次之,其他藻类占比较低;流速在005～010 m/s之间,蓝藻占比下降,硅藻、甲藻及绿藻占比上升,其他藻类占比较低;流速大于010/s时,硅藻占比达到绝对优势。浮游植物细胞丰度随着流速的增加表现出先增加后减小的趋势,两者之间存在单峰关系;不同流速下浮游植物会出现较明显的聚类特征。

Effects of River Hydrology on Phytoplankton Dynamics in Dammed Rivers

The change of river hydrology by damming will affect phytoplankton dynamics, but, currently, the systematic knowledge about this process is very limited. In this study, we investigated phytoplankton, water velocity and related environmental factors seasonally in a river-reservoir system of the Wujiang River. The results showed that the water velocity (v) ranged from 0.01 to 1.32 m/s with an average of 0.32 m/s, and diatoms, cyanobacteria, dinoflagellates were sensitive to the water velocity. Diatoms and cyanophyta dominated when v<0.05 m/s; diatoms, dinoflagellates and chlorophyta dominated when 0.05 m/s <v<0.10 m/s; and diatoms was the only dominated algae when v>0.10 m/s. As the water velocity increasing, the abundance of the phytoplankton cell increased firstly and then decreased, showing an unimodal relationship with the water velocity. In addition, phytoplankton showed obvious clustering characteristics at different flow rates.