In　the　present　study,　a　survey　on　the　aquacultural　environment　and　distribution　characteristics　of　organic　carbon　were　conducted　in　a　typical　mariculture　bay　of　southeast　China　from　January　to　August　2023.　The　spatio-temporal　dynamics　and　sources　of　dissolved　organic　carbon　(DOC)　and　particulate　organic　carbon　(POC)　were　investigated,　as　well　as　the　impact　of　mariculture　on　the　coastal　carbon　cycles.　The　results　showed　that　concentrations　of　DOC　ranged　from　0.488　mg/L　to　2.674　mg/L,　with　an　average　of　1.118　±　0.458　mg/L,　being　lowest　in　January　and　highest　in　August.　DOC　increased　from　the　channel　to　the　estuary　in　January　and　March,　while　the　estuary　was　a　high-value　area　in　April.　Then　DOC　concentrations　decreased　from　west　to　east　in　May　and　June,　while　in　August,　DOC　demonstrated　an　increasing　trend　from　the　west　to　the　east.　The　concentrations　of　POC　ranged　from　0.012　mg/L　to　0.309　mg/L,　with　an　average　of　0.091　±　0.054　mg/L,　being　lowest　in　March　and　highest　in　June.　POC　increased　from　east　to　west.　The　highest　concentrations　of　DOC　and　POC　were　found　at　bivalve　and　kelp　cultivation　areas.　The　non-culture　area　had　the　lowest　concentrations　of　DOC　and　POC.　The　concentrations　of　POC　in　the　bivalve-kelp　multi-trophic　aquaculture　area　were　reduced　by　19.063　%　and　24.711　%　compared　to　single　bivalve　or　macroalgae　aquaculture,　respectively.　Preliminary　analysis　of　the　source　of　organic　carbon　based　on　correlation　analysis,　C/N,　POC/Chl-a　ratios　showed　that　the　living　phytoplankton　and　degraded　organic　matter　were　the　main　source　of　DOC.　The　sources　of　POC　included　microbial-derived　organic　matter,　primary　production　and　runoff　inputs.　This　study　provides　a　scientific　basis　for　environmental　management　and　planning　of　aquaculture　in　the　semi-closed　bays.　©　2025