流速对浮游藻类生长和种群变化影响的模拟试验

采集夏季崇明岛中心湖原水,在环形有机玻璃水槽开展了不同流速对浮游藻类生长和种群变化影响的研究.相对于静止水槽,实验前期不同的流速条件均对浮游藻类的生长产生了一定的抑制作用,实验后期浮游藻类叶绿素a含量均稳定在一定水平,且流动水槽中叶绿素a含量略大于静止水槽,这可能与静止围隔中出现大量枝角类浮游动物有关,而流动条件则抑制了浮游动物的生长,减轻了对浮游藻类的捕食压力.水体流动导致了浮游藻类种群的变化,蓝藻的迅速消失、绿藻和硅藻形成生长优势是主要特征,表明持续的流动条件是导致浮游植物种属减少和群落结构变化的直接原因.该研究可为调水引流在河道、湖泊和水库中的富营养化控制和水华防治提供基础依据.

Simulation experiment on the effect of flow velocity on phytoplankton growth and composition

An experimental simulation study was conducted using surface water from Zhongxinhu Lake of Chongming Island in oval plexiglass enclosures. The object of the study was to investigate the effect of flow velocity on phytoplankton growth and composition dynamics. Both flow conditions had inhibition effects on phytoplankton biomass in early experiment compared with the still enclosure and in late experiment the phytoplankton biomass stabilized in a certain level in all enclosures. Moreover, a higher Chl.a concentration was found in both flow enclosures in the late experiment, implying that numerous Cladocera zooplankton occurred in the still enclosure might be the reason that in flow conditions the turbulent flows inhibited the growth of zooplankton and reduced the predation pressure of phytoplankton. The turbulent flow also resulted in the changes of phytoplankton composition with the feature of the rapid disappearance of blue-green algae and the domination of green algae and diatoms. The result indicated that the continuous flow may directly caused the reducing species and composition dynamics of phytoplankton. The study can provide basis of the application of water division in eutrophication management and algae bloom prevention of rivers, lakes and reservoirs.