Laboratory of Marine Ecological Environmental Early Warning and Monitoring, Third Institute of Oceanography, Xiamen, 361005, China
2.
Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina 29802, USA
Funds:
The Scientific Research Foundation of Third Institute of Oceanography, Ministry of Natural Resources under contract No. 2020012; the Guiding Project of the Science and Technology Plan of Fujian Province under contract No. 2020Y0081; the Natural Science Foundation of Xiamen, China under contract NO. 3502Z20227246
The biogeochemical processes of marine sediments are influenced by bioturbation and organic carbon decomposition, which is crucial for understanding global element cycles and climate change. Two sediment cores were acquired in 2017 from abyssal basins in the central-eastern tropical Pacific to determine the bioturbation and organic carbon degradation processes. The radioactivity concentrations of 210Pb and 226Ra in the sediment cores were measured, indicating the presence of significant excess 210Pb (210Pbex) signals in the sediment cores. Besides, a manganese nodule was discovered in one core, which had a substantial influence on the distribution of 210Pbex. With the exception of this anomalous finding, the bioturbation coefficients in the remaining core were estimated to be 10.6 cm2/a using a steady-state diffusion model, greater than most of the deep-sea sediments from the Equatorial Eastern Pacific. By using a bio-diffusion model, we further calculated the degradation rates of organic carbon (8.02 ka-1), which is also higher than other areas of the Pacific. Our findings displayed the presence of a biologically active benthic ecosystem in the central-eastern tropical Pacific.
Figure 1. Sampling locations in the central-eastern tropical Pacific
Figure 2. Profiles of TOC and water content in two sediment cores. The dots represent the water content, and the square represents the TOC.
Figure 3. Profiles of specific activity of 210Pb and 226Ra (Bq/kg) in two sediment cores
Figure 4. The curve of 210Pb activity from the one-dimensional diffusion module of 222Rn which is escaped from manganese nodule (sediment core TRCEP-S07-MC04)
Figure 5. The relationship between the specific activity of 210Pbex (Bq/kg) and depth (cm) in two sediment cores.
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