Particulate organic carbon cycle at the surface water and sediment in the Ulleung Basin, East/Japan Sea

Abstract

This study investigated organic carbon fluxes in Ulleung Basin surface water and sediments, East/Japan Sea based on a 234Th analysis and geochemical analyses. At depths greater than 2,000 m, Ulleung Basin sediments have high organic carbon contents (over 2.0%). Apparent sedimentation rates (ASR) calculated from excess 210Pb activity distribution, varied from 0.036 to 0.047 cm year-1. The mass accumulation rates (MAR) calculated from porosity, grain density (GD) and ASR, ranged from 131 to 184 g m-2 year-1. These results were in agreement with sediment trap results obtained at a water depth of 2100 m. Input fluxes of organic carbon (IF) varied from 7.89 to 11.08 gC m-2 year-1 at the basin sediments, with an average of 9.56 gC m-2 year-1. Below a sediment depth of 15cm, burial fluxes of organic carbon (BF) ranged from 2.02 to 3.10 gC m-2 year-1. Within the basin sediments, regenerated fluxes of organic carbon (RF) estimated with oxygen consumption rate, varied from 6.22 to 6.59 gC m-2 year-1. However, the regenerated fluxes of organic carbon (RF) calculated by subtracting burial flux from input flux, varied from 5.87 to 7.98 gC m-2 year-1. Respectively, the proportions of the input flux, regenerated flux, and burial flux to the primary production (154.7 gC m-2 year-1) in the Ulleung Basin were about 6.2%, 4.5%, and 1.7%. These proportions were extraordinarily higher than the average of world open ocean. Based upon thescontents (over 2.0%). Apparent sedimentation rates (ASR) calculated from excess 210Pb activity distribution, varied from 0.036 to 0.047 cm year-1. The mass accumulation rates (MAR) calculated from porosity, grain density (GD) and ASR, ranged from 131 to 184 g m-2 year-1. These results were in agreement with sediment trap results obtained at a water depth of 2100 m. Input fluxes of organic carbon (IF) varied from 7.89 to 11.08 gC m-2 year-1 at the basin sediments, with an average of 9.56 gC m-2 year-1. Below a sediment depth of 15cm, burial fluxes of organic carbon (BF) ranged from 2.02 to 3.10 gC m-2 year-1. Within the basin sediments, regenerated fluxes of organic carbon (RF) estimated with oxygen consumption rate, varied from 6.22 to 6.59 gC m-2 year-1. However, the regenerated fluxes of organic carbon (RF) calculated by subtracting burial flux from input flux, varied from 5.87 to 7.98 gC m-2 year-1. Respectively, the proportions of the input flux, regenerated flux, and burial flux to the primary production (154.7 gC m-2 year-1) in the Ulleung Basin were about 6.2%, 4.5%, and 1.7%. These proportions were extraordinarily higher than the average of world open ocean.