Spatial and seasonal variability of surface particulate inorganic carbon and relationship with particulate organic carbo
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ORIGINAL ARTICLE
Spatial and seasonal variability of surface particulate inorganic carbon and relationship with particulate organic carbon in the Yellow‑Bohai Sea Xiujun Wang1 · Jun Yu1 · Hang Fan1 Received: 15 June 2019 / Revised: 28 March 2020 / Accepted: 2 April 2020 © The Oceanographic Society of Japan and Springer Nature Singapore Pte Ltd. 2020
Abstract 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 ( 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. Keywords PIC · Spatial pattern · Seasonal variability · PIC:POC ratio · The Yellow-Bohai Sea
1 Introduction The marginal sea covers only about 7% of the total ocean surface area. However, it plays an important role in the global carbon cycle because it accounts for 15–30% of oceanic primary production globally (Wang et al. 2005), ~ 80% of organic matter burial and ~ 30 to 50% of the deposition of calcium carbonate (Bauer et al. 2013). There have been studies showing that the carbon cycle in marginal seas are influenced by complex processes associated with the varying hydrodynamic conditions, and strong land-sea interactions and anthropogenic impacts (Bianchi and Allison 2009; Liu et al. 2015b; Zhang et al. 2016). The Yellow-Bohai Sea (YBS) is a typical marginal sea of China, which shows large variations in air–sea C O2 fluxes * Xiujun Wang [email protected] 1
College of Global Change and Earth System Science, Beijing Normal University, No. 19 Xinjiekouwai Street, Beijing 100875, People’s Republic of China
over space and time. Earlier studies showed that north Yellow Sea is a net CO2 source in all seasons (Xue et al. 2012) whereas south Yellow Sea is a weak C O2 sink during late spring and summer (Qu et al. 2014). A recent synthesis suggests that the Bohai Sea acts as a CO2 source, but the Yellow Sea a C O2 sink (Jiao et al. 2018). There are a few reports of total organic carbon (TOC) in the sediments of the Bohai Sea and north Yellow Sea, which show large spatial variability, with the highe
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