Research On The Response Of The Structure And Function Of River Primary Ecosystem To Water Flow Regulation Technology

Due to the impact of human activities such as water storage and dam construction on rivers,some river flows have decreased,and under suitable nutrient conditions,there is an increased risk of Periphyton proliferation,leading to the deterioration of the water ecological environment and the destruction of water sources.A large number of studies have shown that water flow regulation technology is a new type of Periphyton management method,but the response mechanism of water flow factors to alleviate the abnormal proliferation of Periphyton is still unclear.This study focuses on low flow river sections,simulates the process of flow cascade changes through a water tank,and the pulse process of high discharge from dams.The aim is to explore effective methods for hydraulic regulation of abnormal proliferation of Periphyton and the response mechanism of primary ecosystems.The main research results are as follows:（1）The spatiotemporal changes of Periphyton were studied through simulated water tank experiments,and the mechanism of the effect of water flow velocity on Periphyton was explored.The results indicate that there is a significant negative correlation between water flow velocity and the biomass of Periphyton.Compared to the low flow rate scenario（0.086m/s）,at a flow rate of 0.418 m/s,the biomass of algae decreased by 39.88%,and the community structure began to aggregate towards filamentous algae.The change in community structure from diatoms to filamentous green algae was 87.53%.Significant differences in biodiversity,speciesαThe diversity index is influenced by physical and chemical environmental factors,especially flow velocity.（2）By comparing the results of single pulse interference with multiple pulses,it was found that there were significant differences in the resistance of different Periphyton to hydrodynamic flushing.Diatoms showed a positive response to pulse interference and rapidly decreased biomass.In addition,at a flow rate of 1.000 m/s,the biomass was effectively reduced by 80%within 15 minutes,inhibiting the proliferation of algae.However,there was a rebound phenomenon in single pulse interference.Multiple pulse interference continued to reduce biomass and increase the diversity of primary producers,playing a key role in regulating Periphyton growth,which is conducive to the stability of river ecosystems.（3）Based on the high-throughput sequencing technology of 16s rRNA,the response relationship between the microbial community structure and environmental function indicators in the simulated flume was analyzed under the background of stepped flow increase.The results showed that,except for DO,environmental functional indicators such as GPP and ER,as well as water quality indicators such as Chla,TN,TP,NO₃^-,all showed positive ecological responses to ecosystem structure and function.The bacteria Undibacterium and Acidovarax have a positive response to changes in water flow.The bacterial community mainly focuses on basic biological functions,and improves water quality through the restoration of microbial community functions.In summary,this study elucidates that flow velocity is the main environmental variable leading to changes in the structure of algal communities,and also the main indicator affecting changes in algal communities in rivers.Research has revealed that regulating flow velocity can improve river ecosystems and have good effects on both typical and functional indicators of rivers.The research results have broadened the scientific understanding of hydrological restoration in low flow river sections,preliminarily solved the technical problems of regulating and managing algal blooms and ecological environment protection and restoration in low flow river sections,and have certain theoretical and practical value.