Sea　level　rise-induced　salinization　is　projected　to　influence　the　decomposition　of　soil　carbon　(C)　in　tidal　wetlands.　Despite　evidence　showing　that　microbial　metabolism　can　determine　the　fate　of　soil　C　decomposition,　the　response　of　microbial　metabolism　to　salinization　in　tidal　wetlands　remains　largely　unknown.　Microbial　metabolism　is　impacted　by　the　microbial　metabolic　limitation　and　carbon　use　efficiency　(CUE),　which　can　provide　mechanistic　insights　into　soil　C　decomposition.　Here,　we　measured　microbial　metabolic　limitation,　microbial　CUE,　and　extracellular　enzyme　activities　along　an　estuarine　salinity　gradient　ranging　from　freshwater　(0.1　+/-　0.1　mg　g(-1))　to　oligohaline　(2.1　+/-　0.5　mg　g(-1))　in　a　tidal　wetland.　Overall,　microorganisms　were　limited　by　phosphorus　(P)　in　the　tidal　wetlands,　where　salinization　increased　microbial　P　limitation　by　34%.　The　enhanced　microbial　P　limitation　was　attributed　to　increases　in　soil　C:P　and　belowground　biomass,　as　well　as　decreases　in　root　C:P　with　increasing　salinity.　Microbial　CUE　decreased　from　0.38　to　0.33　as　salinity　increased,　while　microbial　P　limitation　was　negatively　correlated　with　microbial　CUE,　representing　the　trade-off　between　the　two.　Furthermore,　microbial　P　limitation　was　positively　associated　with　C5　nitrogen　(N)5　and　P-acquiring　extracellular　enzyme　activities,　while　all　these　enzyme　activities　were　negatively　correlated　with　microbial　CUE.　These　results　illustrate　that　to　balance　microbial　P　limitation　with　salinization,　microorganisms　transfer　more　energy　from　the　microbial　CUE　to　extracellular　enzyme　production,　and　this　was　the　mechanism　underlying　the　tradeoff.　Microorganisms　were　also　limited　by　C　in　the　tidal　wetlands.　However,　as　the　increasing　belowground　biomass　alleviated　microbial　C　limitation　with　salinization,　no　relationship　was　observed　between　microbial　C　limitation　and　CUE.　Future　C　and　nutrient　models　aimed　to　simulate　tidal　wetland　ecosystem　responses　to　salinization　will　benefit　from　the　inclusion　of　trade-off　between　microbial　CUE　and　microbial　P　limitation　for　more　accurate　prediction.