Intensive　aquaculture　in　estuaries　and　coasts　has　resulted　in　several　ecological　and　environmental　problems.　Among　various　nitrogen　transformation　pathway,　dissimilatory　nitrate　(NO3-)　reduction　is　considered　to　be　highly　important　in　regulating　reactive　nitrogen.　However,　there　are　relatively　few　studies　on　the　processes　and　contribution　of　NOx-　reduction　in　sediment　during　the　shrimp　pond　culture　period.　Three　sediment　NO3-　reduction　processes,　denitrification　(DNF),　anaerobic　ammonium　oxidation　(ANA),　and　dissimilatory　NO3-　reduction　to　ammonium　(DNRA),　were　surveyed　in　eight　shrimp　ponds　across　three　subtropical　estuaries　using　N-15　isotope　tracing　experiments.　The　rates　of　DNF,　ANA　and　DNRA　ranged　from　2.87-18.11,　0.10-1.92,　and　0.21-1.25　nmol　N　g　(-1)　h　(-1),　respectively.　DNF　was　responsible　for　64.2-91.6%　of　the　total　NO3-　reduction.　Regarding　environmental　factors,　C　and　N　substrates,　as　well　as　salinity,　significantly　affected　NO3-　reduction.　In　general,　the　N　losses　were　approximately　32.43-131.64　g　N　m(-2)　yr(-1)　for　DNF　and　2.38-15.85　g　N　m(-2)　yr(-1)　for　ANA　in　this　study,　indicating　that　coastal　reclamation　is　a　nonnegligible　way　to　remove　nitrogen.　Our　results　provide　a　scientific　foundation　for　understanding　the　mechanism　of　nitrogen　cycling　in　the　artificial　aquatic　environment　of　shrimp　ponds.