Bioturbation coefficients and organic carbon degradation rates of deep-sea sediments in the central-eastern tropical Pacific

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 (²¹⁰Pb_ex) signals in the sediment cores. Besides, a manganese nodule was discovered in one core, which had a substantial influence on the distribution of ²¹⁰Pb_ex. 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.