Environmental factors affecting regional differences and decadal variations in the buried flux of marine organic carbon in eastern shelf sea areas of China

To characterize environmental factors controlling decadal-scale variations in the buried flux of marine organic carbon(BF_(C_m)) in the eastern shelf sea areas of China(ECSS),four well preserved sediment cores collected from the central Yellow Sea mud(CYSM) area,the Yellow Sea Coastal Current(YSCC) area and the Changjiang River Estuary(CRE) were investigated in this study.In the CYSM,variations in BF_(C_m) were found to be dependent on variations in primary productivity and to exhibit a cyclical trend possibly related to fluctuations in the Pacific Decadal Oscillation(PDO) and the East Asian winter monsoon index(EAWM).In the YSCC,BF_(C_m) likewise depends on primary productivity.Prior to the 1950s,variations in BF_(C_m) were similar to that of the EAWM.After the 1950s,BF_(C_m) increased rapidly and exhibited maximum values in the surface layer,consistent with an increase in primary productivity caused by the input of terrestrial nutrients associated with China's economic development.In the CRE,variations in BF_(C_m) were affected by several competing factors making it difficult to identify clear relationships between variations in BF_(C_m) and primary productivity.In contrast,long-term variability in BF_(C_m) is more similar to changes in the Changjiang River sediment load.Thus,it is speculated that the construction of dams along the Changjiang River may be the main cause of variations in BF_(C_m) in this area.Given the disproportionate effects of human activities on marine environments and decadal variations in BF_(C_m) in the ECSS,careful attention should be paid to regional differences in organic carbon preservation and environmental changes lest estimates of these values be made imprecise or inaccurate.