106 / 2023-07-30 22:53:50

Sources and Dynamic Cycling of Dissolved Organic Carbon in the South China Sea

South China Sea,Dissolved organic carbon,North Pacific Ocean,Kuroshio intrusion

The cycling of oceanic dissolved organic carbon (DOC) is a crucial component of the global carbon cycle, yet the identification of sources and the mechanisms of its molecular transformation remain poorly understood. As the world's largest marginal sea, the South China Sea (SCS) acts as a mini-oligotrophic ocean with the influence of riverine input and stronger vertical mixing compared with the adjacent North Pacific Ocean (NPO). It provides a natural "reactor" for the study of the DOC biogeochemical cycle along the mixing gradient of terrestrial input and the nutrient supply. This study connected DOC's molecular and carbon isotopic pattern along the continuum from the Pearl River Estuary (PRE) to the SCS and NPO. The combination of stable and radiocarbon isotopes, biomarkers, and high-resolution mass spectrometry analysis separated the terrestrial and oceanic sources and the transformation between the labile and refractory DOC. And we evaluate the dynamic cycling of DOC along the advective and vertical mixing in the SCS and their biogeochemical impacts on the carbon and nutrients supply.