间歇性降雨对香溪河库湾水华及浮游植物演替的影响OA

The mechanisms underlying algal bloom suppression in response to rainfall-induced multi-dimensional and multi-factor changes in aquatic environments remain unclear.This study conducted high-frequency monitoring of three intermittent rainfall events in September 2023 in the Xiangxi River Reservoir Bay,categorized as Type Ⅰ rainfall(short-duration,high-intensity),Type Ⅱ rainfall(long-duration,low-intensity),and Type Ⅲ rainfall(long-duration,moderate-intensity),to investigate the influence of rainfall sequences on bloom dynamics and phytoplankton succession.Results indicate that during the rainfall period,microscopic examination identified 93 genera of phytoplankton belonging to 10 phyla.The dominant species in Cyanophyta were Microcystis and Pseudanabaena;in Bacillariophyta,the dominant species were Cyclotella and Fragilaria;and in Chlorophyta,the dominant species was Chlorella vulgaris.Rainfall type strongly influenced bloom responses,exhibiting a three-phase pattern:following Type Ⅰ rainfall,chlorophyll-a(Chl-a)concentration dropped sharply by 73.7％before rapidly returning to pre-rainfall levels;after Type Ⅱ rainfall,Chl-a showed a fluctuating downward trend;and during and after Type Ⅲ rainfall,Chl-a remained at low levels below 5 μg/L.Phytoplankton community composition responded distinctly to the three rainfall types:Cyanobacteria dominated during Type I and Ⅱ events,whereas the proportion of Bacillariophyta(diatoms)increased significantly after Type Ⅲ rainfall,indicating a shift from cyanobacterial to diatom dominance.Diversity indices analysis showed that both species richness and community diversity declined following rainfall.Correlation analysis revealed that key environmental factors shaping phytoplankton structure included water temperature,dissolved oxygen,pH,conductivity,water level,and flow rate.The cumulative effects of intermittent rainfall,through the synergistic action of environmental stress induced by earlier rainfall events,contributed to bloom suppression.These findings provide a theoretical basis for utilizing artificial rainfall regulation as a strategy for algal bloom control.