Program

 East Asian monsoon and mesoscale eddy are known to regulate the primary production in South China Sea (SCS), the largest tropical marginal sea, their contribution to the deep biogenic flux are yet to be evaluated. We present results from 7-years time series sediment trap observation at 1200 m in the central SCS that quantified  averaged monthly sinking biogenic fluxes, and combined with remote sensing physical parameters to evaluate impact of mesoscale cyclonic eddy on biogenic fluxes. The averaged monthly POC and opal fluxes ranged from 3.0~5.2 mg m^-2 d^-1and 14.8~34.9 mg m^-2 d^-1, with higher values during northeastern monsoon corresponding to deeper mixed layer depth and higher NPP which related to nutrient supply controlled by monsoon transition and surface cooling. Vice versa, lower POC and opal fluxes occurred during well-stratified inter-monsoon periods. By contrast, CaCO₃ flux (23.6~37.0 mg m^-2 d^-1) had less seasonality and no correlation with surface nitrate concentration, but related to foraminifera abundance. However, the long-term time series variation of biogenic fluxes decoupled with upper water mixing, suggesting other processes may impact interannual variability of biogenic fluxes besides wind and surface heat flux. The inverse relationship between five large particle pulses and sea surface height anomaly confirmed the role of cyclonic eddies in the observed higher biogenic fluxes. Finally, we present that the POC flux collected at mid-depth in the central SCS increased by 22% is contributed by cyclonic eddy-driven processes via diatom bloom making the biological carbon pump more efficient in CO₂ sequestration during northeastern monsoon period.