Spatial and seasonal variability of surface particulate inorganic carbon and relationship with particulate organic carbon in the Yellow-Bohai Sea

Particulate carbon is one of the major carbon forms in seawater, thus plays an important role in the carbon cycle. Limited small scale studies showed that particulate inorganic carbon (PIC) content was much higher than particulate organic carbon (POC) in the Yellow River Estuary. This study is to test the hypothesis that surface PIC is significantly higher than POC in the Yellow-Bohai Sea (YBS). Using the PIC and POC data derived from MODIS-Aqua during 2002–2016, we find that mean PIC:POC ratio is ~ 2 in the water column for the whole YBS. Overall, PIC is significantly higher in the nearshore waters (> 600 mg m−3) than in the offshore, with the lowest found in the center of the south Yellow Sea (< 100 mg m−3). There is a tongue shaped area with year-around high PIC value (> 600 mg m−3) near the Old Yellow river estuary where POC level is not so high comparing with other sections. Surface PIC in the YBS shows a strong seasonality, i.e., highest in winter and lowest in summer, which is largely attributable to strong sediment resuspension in winter and strong stratification in summer. Our analyses indicate that sediment resuspension and water exchange are dominant factors regulating the seasonal and spatial variability of PIC in the YBS.