Burial of Organic Carbon in the Taiwan Strait

Abstract

Organic carbon (OC) burial in nondeltaic continental shelves is an important part of the global carbon cycle. Of these, the Taiwan Strait (TWS) is a typical, nondeltaic shelf region that is influenced by a variety of factors including strong ocean currents, coastal upwelling, and small river inputs. To better understand how these factors influence OC burial in the TWS, we measured total organic carbon and total nitrogen contents as well as the stable carbon isotopes of sedimentary organic matter (δ13Corg) from the TWS. We also measured glycerol dialkyl glycerol tetraethers in surface sediments collected from the TWS. The concentrations of sedimentary total organic carbon and total nitrogen along the coast were high but decreased in areas more central to the TWS. This gradient was controlled by both hydrological conditions and coastal upwelling. The calculated accumulation rate of organic carbon ranged from 1.9 to 47.2 g C/m2/year and was comparable to other areas of the Chinese marginal seas. The source contribution calculated from the three-end-member model revealed that mostly marine OC was buried in the upwelling regions. In comparison, OC derived from terrestrial plant and soil was buried in the estuaries. Collectively, these results showed that the TWS may serve as a CO2 sink in the global carbon cycle. This is due to the preservation of the labile portions of the OC derived from plant and marine source, which formed the main component of the buried OC in the TWS.