The biogeochemical cycles of sulphur (S),iron(Fe) and nitrogen (N) elements play a key role in the reservoir ecosystem.However,the spatial positioning and interrelationship of S,Fe and N cycles in the reservoir sediment profile have not been explored to a greater extent.Here,we measure the gradients of Fe2+,SO42-,NO3-,NH4+,DOC,TC and TN in the pore water of the sediment,and combining the vertical distribution of the functional microorganisms involved in S,Fe and N cyclings in the sediments to determine the redox stratification in the sed-iment.It is found that the geochemical gradient of S,Fe and N of the reservoir sedimentary column is mainly defined by the redox process involved in the related func-tional microorganisms.According to the type of electron acceptor,the sediment profile is divided into 3 redox intervals,namely aerobic respiration (0-10 cm),denitrifi-cation/iron reduction (10-28 cm) and sulfate reduction(28-32 cm).In the aerobic respiration zone,NH4+ is oxi-dized by aerobic AOB to NO3-(0-5 cm),and Fe2+ is oxidized by microaerobic FeRB to Fe3+ (3-10 cm).In the denitrification/iron reduction zone,Acinetobacter and Pseudomonas,as the dominant NRB genera,may use nitrate as an electron acceptor to oxidize Fe2+ (11-16 cm).The dominant genera in SOB,such as Sulfururvum,Thiobacillus and Thioalkalispira,may use nitrate as an electron acceptor to oxidize sulfide,leading to SO42-accumulation (14-24 cm).In the sulfate reduction zone,SO42-is reduced by SRB.This study found that functional microorganisms forming comprehensive local ecological structures to adapt to changing geochemical conditions,and which would be potentially important for the degra-dation and preservation of C and the fate of many nutrients and contaminants in reservoirs.