ORGANIC CARBON CYCLE IN THE ULLEUNG BASIN SEDIMENT, EAST/JAPAN SEA

Abstract

Organic carbon (OC) fluxes in the Ulleung Basin (UB) sediments, East/Japan Sea (E/JS) were investigated through geochemical analyses and sediment chamber experiment. The UB sediment has high organic carbon contents of over 2% and the mean C/N molar ratio is 7.09, therefore suggesting that the organic matter deposited in the UB is predominantly of marine origin. Apparent sedimentation rates (ASR) calculated from excess Pb-210 activity distribution, ranged between 0.036-0.047 cm year(-1). The mass accumulation rates (MAR) calculated from porosity, grain density (GD) and ASR, ranged between 131-184 g m(-2) year(1). Input fluxes of OC (IF) and burial fluxes of OC (BF) varied between 7.89-11.08 and 2.02-3.10 gC m(-2) year(-1), respectively. Regenerated fluxes of OC (RF) estimated with oxygen consumption rate, varied between 6.22-6.59 gC m(-2) year(-1). However, the RF calculated by subtracting BF from IF, varied between 5.87-7.98 gC m(-2) year(-1). The proportions of the IF, RF, and BF to the primary production (177.1 gC m(-2) year(-1)) in the UB were about 5.4%, 3.9%, and 1.5%, respectively. These proportions were over 5 times higher than the average of world open ocean. Based on these results, the UB appears to play an important role in the deposition and removal of organic carbon in the E/JS.