Main Geochemical Characteristics and Key Biogeochemical Carbon Processes in the East China Sea

Abstract

Research related to carbon geochemistry and biogeochemistry in the East China Sea is reviewed in this paper. The East China Sea is an annual net sink for atmospheric CO2 and a large net source of dissolved inorganic carbon to the ocean. The sea absorbs CO2 from the atmosphere in spring and summer and releases it in autumn and winter. The East China Sea is a CO2 sink in summer because Changjiang River freshwater flows into it. The net average sea-air interface carbon flux of the East China Sea is estimated to be about 4.3 × 106 t/y. Vertical carbon transport is mainly in the form of particulate organic carbon in spring; more than 98% of total carbon is transported in this form in surface water, and the number exceeds 68% in water near the bottom. In the southern East China Sea, the average particulate organic carbon inventory was about one-tenth that of the dissolved organic carbon. Research indicates that the southern Okinawa Trough is an important site for particulate organic carbon export from the shelf. The annual cross-shelf exports are estimated to be 414 and 106 Gmol/y for dissolved organic carbon and particulate organic carbon, respectively. Near-bottom transport could be the key process for shelf-to–deep sea export of biogenic and lithogenic particles.