Coastal　wetlands　are　among　the　most　carbon-rich　ecosystems　in　the　world.　Litter　decomposition　is　a　major　process　controlling　soil　carbon　input.　Non-additive　effect　of　litter　mixture　on　decomposition　has　been　observed　in　many　terrestrial　plants　but　rarely　tested　in　coastal　species.　We　selected　three　common　mangrove　species　and　one　saltmarsh　species　co-occurring　in　subtropical　coasts　to　test　whether　the　non-additive　effect　occurs　when　their　litters　mixed　together,　and　how　the　nutrients　release　into　water　are　impacted　consequently.　A　litter-bag　experiment　was　carried　out　in　a　glasshouse　with　single　and　mixed　leaf　litters.　Non-additive　effects　were　observed　in　the　litter　mixtures　of　mangrove　species　Aegiceras　corniculatum　vs.　Kandelia　obovata　(antagonistic)　and　A.　corniculatum　vs.　Avicennia　marina　(synergistic),　but　not　in　the　litter　mixtures　of　A.　corniculatum　(mangrove　species)　vs.　Spartina　alterniflora　(saltmarsh　species).　The　strength　of　the　non-additive　effect　was　unrelated　to　the　initial　trait　dissimilarity　of　litters.　Instead,　the　decomposition　rate　and　mass　remaining　of　litter　mixtures　were　strongly　related　to　the　carbon　concentrations　in　litter　mixtures.　Nutrient　content　in　waters　was　dependent　on　the　decomposition　rate　of　litter　mixtures　but　not　on　the　initial　nutrient　concentrations　in　litters.　Despite　the　behind　mechanisms　were　not　yet　revealed　by　the　current　study,　our　findings　have　improved　the　understanding　of　the　litter　decomposition　of　coastal　species　and　the　consequent　nutrient　release.