Sediment and biogenic matter accumulation in the Sea of Okhotsk

Abstract

Three sediment cores were collected at the western shelf and at the basin (1300 m deep) of the Okhotsk Sea. Sediment accumulation and sediment parameters were obtained using down core distribution of excess 210Pb based on one dimensional, two-layer, steady-state constant 210-Pb flux, constant sedimentation rate model in which mixing occurs only in the surface ixed layer. Sediment accumulation rate varies from 115 to 212 and 13 mg cm(-2) yr(-1) in the western shelf and deep basin, respectively. Surface mixed layers varied from 11 to 12 and 10 cm in the shelf and basin, respectively. Mixing coefficient is 4 to 9 and 2 cm(-2) yr(-1) in the shelf and basin, respectively. Particle residence time in the surface mixed layer is ca. 50 and 80 years in the shelf and basin, respectively. Steady state excess 210Pb flux to the sediment surface is about 2 to 3 dpm cm(-2) yr(-1). In the surface sediment, organic carbon concentration varies from 1.0 to 1.2% and 1.4-1.5% in the shelf and basin, respectively. Biogenic silica content varies from 3.4 to 4.2% and 16.5-19.1% in the shelf and basin, respectively. Sediment incorporation of particulate biogenic matter is at least 1.8 mg C cm(-2) yr(-1) and 2.9 mg Si cm(-2) yr(-1) in the shelf and 0.2 mg C cm(-2) yr(-1) and 2.2 mg Si cm(-2) yr(-1) in the basin.