Abstract
To evaluate the sources and budgets of sedimentary organic matter in the East China Sea (ECS), bulk organic matter properties (total organic carbon (TOC), C/N ratio, carbon and nitrogen isotopic composition (δ13C and δ15N)) and sterols in surface sediments were analyzed. The distributions of bulk organic matter properties and sterols showed a strong regionality with higher contents in the southern inner shelf as well as the offshore upwelling area. It was consistent with the increasing mud and chlorophyll a (Chl a) contents southwards. These distribution patterns were attributed to the terrestrial inputs by shelf circulations and phytoplankton contribution. Both of bulk organic matter properties and sterols indicated a mixture of terrestrial and marine derived organic matter inputs with marine source as a dominant input. Budgets suggested that organic carbon (OC) and sterol influxes from terrestrial source were 5.15×106 and 3.32×103t/yr, with the Changjiang River input as the primary contributor; and while their influxes from marine source were 26.3×106 and 2.19×103t/yr, respectively. The burial fluxes of OC and sterol were 3.99×106tC/yr and 0.21×103t/yr, with the inner shelf as main accumulation area. Although there was a huge amount of OC influx from terrestrial and marine sources, but only 24.6% and 10% of them could be preserved in sediments. Consequently, the combined effect of riverine input, marine primary productivity and deposition decided the organic matter behaviors in the ECS.
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