In the slope settings of marginal sea systems, lateral transport of particulate matter may provide allochthonous particulate organic carbon (POC) to the ocean interior, which in turn has implications for assessing the strength and efficiency of the modern biological carbon pump (BCP). However, the relative contributions of POC from different sources in the mesopelagic of marginal seas are still poorly understood. In this study, we collected sinking particulate matter from the northern South China sea during November 2020 to May 2022 using a time-series sediment trap. Geochemical parameters such as organic carbon, nitrogen, and biogenic silica in particulate matter were determined, combining with the remote sensing data of chlorophyll and sea surface height (SSH) to quantify the relative contributions of vertical and lateral transport of POC in the  mesopelagic zone of the northern South China Sea. The results showed that POC derived from surface ocean primary productivity accounted for 50.98%~79.99% of the total sinking POC flux, while the contribution of lateral transport accounted for 20.01%~49.02%, indicating that the contribution of lateral transport should not be neglected when assessing the efficiency of BCP. In addition, the combination of satellite chlorophyll and SSH data suggests that the westward mesoscale eddy may be responsible for the peak of lateral POC flux in April 2021.This study quantitatively assesses the relative contributions of various sources of POC in the mesopelagic zone of the northern South China Sea, offering a scientific basis for further research into the role of lateral transport within marginal sea systems.

 

biological carbon pump, lateral transport, particulate organic carbon, northern South China Sea, mesoscale eddies