Sedimentary organic carbon burial in marine oxic sediments modulated by anticyclonic eddy

Abstract

Anticyclonic eddies (AEs) are a common feature of ocean circulation and play a significant role in influencing the rates of carbon fixation and export. However, the mechanism underlying organic carbon (OC) export and sedimentation modulated by AEs are poorly deciphered. Here, we utilized in-situ observations of dissolved oxygen, chlorophyll, pH, and turbidity in the water column and experimental analyses of molecular biomarkers, OC, and iron trioxide in sediments from the East China Sea, to unravel the processes driving OC sedimentation modulated by AE. Our findings reveal that a significant amount of OC is preserved in oxic sediments, influenced by the presence of an anticyclonic eddy. We suggest that the eddy promotes the accumulation of OC along its periphery, and transports OC downward under the pycnocline. The combination of OC with iron trioxide, facilitated by oxidation, impedes the mineralization of OC in sediments. The accumulation of OC in oxic sediment, modulated by anticyclonic eddies, has significant implications for OC burial in mid-latitude oceans on millennial timescales.