Organic Carbon Oxidation in the Sediment of the Ulleung Basin in the East Sea

Abstract

We characterized the biogeochemical organic carbon (Corg) cycles in the surface sediment layer of the Ulleung Basin (UB) of the East Sea. The total oxygen uptake (TOU) rate and the diffusive oxygen uptake (DOU) rate of the sediment were measured using an autonomous in situ benthic lander equipped with a benthic chamber (KIOST BelcII) and a microprofiler (KIOST BelpII). The TOU rate was in the range of 1.51 to 1.93 mmol O2 m−2 d−1, about double the DOU rate. The high TOU/DOU ratio implies that the benthic biological activity in the upper sediment layer is one of the important factors controlling benthic remineralization. The in situ oxygen exposure time was about 20 days, which is comparable to the values of other continental margin sediments. The sedimentary Corg oxidation rates ranged from 6.4 to 6.5 g C m−2 yr−1, which accounted for ~2% of the primary production in UB. The Corg burial fluxes ranged from 3.14 ± 0.12 to 3.48 ± 0.60 g C m−2 yr−1, corresponding to more than 30% of the deposited Corg buried into the inactive sediment deep layer.