Historical Reconstruction of Organic Carbon Decay and Preservation in the Sediment on the East China Sea Shelf

Tuesday, 16 December 2014
Xinxin Li, Taxas A&M University, College Station, TX, United States, Thomas S Bianchi, University of Florida, Gainesville, FL, United States, Mead A Allison, The Water Institute of the Gulf, Batn Rouge, LA, United States, Piers Chapman, Texas A&M University, College Station, TX, United States and Guipeng Yang, Ocean University of China, Qingdao, China
Sediment cores were collected from the East China Sea inner shelf in 2010 to study the decay and preservation of organic carbon (OC). The results showed that the average total OC content was higher at inner shelf stations than those offshore. The δ13C was more depleted at nearshore than offshore stations. Principal component analysis indicated that terrestrial OC, as indicated by lignin-phenols values, was preserved in sediment closer to the coast while offshore sediment was more composed of lignin-poor degraded OC, that was likely hydrodynamically sorted. Marine-derived OC, as indicated by plant pigments, was significantly more abundant in the sediment mixed layer than the underlying accumulation layer. Historical flooding events were detected in lignin-phenols profiles in two of the six cores located at mid-shelf stations. Despite the magnitude of the 2010 flood in East China, we did not see any signature of this event with the chemical biomarker in these two cores used in this study. This may suggest that reduced sediment loading due to recent dam construction may have greatly decoupled river inputs with sediment loading to shelf sediment. This work further supports the need for more research to better understand how the reduced inputs of fluvial input of sediments from Chinese rivers (due to river diversions and dams) affect carbon cycling in the East China Sea.