Widespread influence of resuspended sediments on oceanic particulate organic carbon

Particulate organic carbon (POC) in the ocean oftentimes exhibits lower radiocarbon isotope ratios (Delta C- 14) than expected if its sole source were POC recently produced by primary production and export from the overlying surface waters. We have observed a strong correlation between Delta C-14 values of organic carbon and aluminum content in sinking particles. This correlation is remarkably consistent over a range of oceanic settings. The correlation implies that old organic carbon associated with lithogenic material from sediment resuspension is responsible for the radiocarbon-depleted values of oceanic POC (as opposed to other processes such as incorporation of dissolved inorganic carbon or dissolved organic carbon into POC at depth). Resuspension of sediment and its subsequent lateral transport therefore appears to be an important component of oceanic carbon cycle, particularly over or adjacent to continental margins, and requires consideration in models of carbon export and burial.