Increased　nitrogen　(N)　loading　and　sea-level　rise　(SLR)　are　two　dominant　drivers　of　global　change　that　threaten　tidal　marshes　and　the　ecosystem　services　they　provide,　including　the　sequestration　of　organic　carbon.　Nevertheless,　the　mechanisms　through　which　N　loading　enrichment,　SLR　inundation　increase,　and　their　combined　effects　impact　the　rates　and　pathways　of　soil　organic　carbon　(SOC)　mineralization　in　tidal　marshes　remain　poorly　understood.　We　utilized　a　factorial　design　in　an　oligohaline　tidal　marsh,　utilizing　in　situ　weirs　to　simulate　SLR　inundation　increase　by　manipulating　the　duration　of　flooding　with　or　without　nitrogen　enrichment　as　NaNO3　plus　NH4Cl　or　with　a　combination　of　increased　flood　duration　and　nitrogen.　After　nearly　2　years,　the　addition　of　N　increased　total　SOC　mineralization　(CMR),　soil　microbial　Fe(III)　reduction　(FeRR),　NO3–　reduction　(NRR),　and　SO42–　reduction　(SRR)　but　decreased　methanogenesis　(MGR).　The　abiotic　factor　Fe(III)/Fe(II)　ratio　and　dissolved　organic　carbon　(DOC),　and　the　biotic　factors,　β-glucosidase　(BG),　and　phenol　oxidase　(PHO)　activity　explained　the　increased　SOC　mineralization　rates　following　N　enrichment.　Increased　flood　duration　did　not　change　CMR,　but　increased　flooding　offset　the　stimulatory　effects　of　N　addition　on　CMR,　FeRR,　SRR,　NRR　and　MGR.　The　contributions　of　Fe(III)　reduction　and　SO42–　reduction　pathways　to　SOC　mineralization　increased　in　all　experimental　treatments,　FeRR,　SRR,　NRR,　and　MGR　were　significantly　positively　correlated　with　the　abundance　of　Geobacter,　dsrA,　nrfA,　and　mcrA.　SLR　inundation　increase　did　not　increase　soil　carbon　loss　in　this　oligohaline　marsh　and　may　counteract　the　simulation　of　soil　C　loss　due　to　N　enrichment.　©　2024