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High nitrate (NO3-) loading in water bodies is a crucial factor inducing the eutrophication of lakes.We tried to enhance NO3-reduction in overlying water by coupling sediment microbial fuel cells (SMFCs) with submerged aquatic plant Ceratophyllum demersum.A comparative study was conducted by setting four treatments:open-circuit SMFC (Control),closed-circuit SMFC (SMFC-c),open-circuit SMFC with C.demersum (Plant),and closed-circuit SMFC with C.demersum (P-SMFC-c).The electrochemical parameters were documented to illustrate the bio-electrochemical characteristics of SMFC-c and P-SMFC-c.Removal pathways of NO3-in different treatments were studied by adding quantitative 15NO3-to water column.The results showed that the cathodic reaction in SMFC-c was mainly catalyzed by aerobic organisms attached on the cathode,including algae,Pseudomonas,Bacillus,and Albidiferax.The oxygen secreted by plants significantly improved the power generation of SMFC-c.Both electrogenesis and plants enhanced the complete removal of NO3-from the sediment-water system.The complete removal rates of added 15N increased by 17.6％ and 10.2％ for SMFC-c and plant,respectively,when compared with control at the end of experiment.The electrochemical/heterotrophic and aerobic denitrification on cathodes mainly drove the higher reduction of NO3-in SMFC-c and plant,respectively.The coexistence of electrogenesis and plants further increased the complete removal of NO3-with a rate of 23.1％.The heterotrophic and aerobic denitrifications were simultaneously promoted with a highest abundance of Flavobacterium,Bacillus,Geobacter,Pseudomonas,Rhodobacter,and Arenimonas on the cathode.