Articles | Volume 11, issue 23
Biogeosciences, 11, 6895–6914, 2014
https://doi.org/10.5194/bg-11-6895-2014
Biogeosciences, 11, 6895–6914, 2014
https://doi.org/10.5194/bg-11-6895-2014

Research article 10 Dec 2014

Research article | 10 Dec 2014

Transfer of organic carbon through marine water columns to sediments – insights from stable and radiocarbon isotopes of lipid biomarkers

S. G. Wakeham1 and A. P. McNichol2 S. G. Wakeham and A. P. McNichol
  • 1Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA
  • 2National Ocean Sciences Accelerator Mass Spectrometer Facility (NOSAMS), Woods Hole Oceanographic Institution, McLean Laboratory, Mail Stop #8, 266 Woods Hole Road,Woods Hole, MA 02543-1539, USA

Abstract. Compound-specific 13C and 14C compositions of diverse lipid biomarkers (fatty acids, alkenones, hydrocarbons, sterols and fatty alcohols) were measured in sinking particulate matter collected in sediment traps and from underlying surface sediments in the Black Sea, the Arabian Sea and the Ross Sea. The goal was to develop a multiparameter approach to constrain relative inputs of organic carbon (OC) from marine biomass, terrigenous vascular-plant and relict-kerogen sources. Using an isotope mass balance, we calculate that marine biomass in sediment trap material from the Black Sea and Arabian Sea accounted for 66–100% of OC, with lower terrigenous (3–8%) and relict (4–16%) contributions. Marine biomass in sediments constituted lower proportions of OC (66–90%), with consequentially higher proportions of terrigenous and relict carbon (3–17 and 7–13%, respectively). Ross Sea data were insufficient to allow similar mass balance calculations. These results suggest that, whereas particulate organic carbon is overwhelmingly marine in origin, pre-aged allochthonous terrigenous and relict OC become proportionally more important in sediments, consistent with pre-aged OC being better preserved during vertical transport to and burial at the seafloor than the upper-ocean-derived marine OC.

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Short summary
Compound-specific δ13C and Δ14C of lipids show that marine organic carbon (OC) in Black and Arabian Sea sediment trap material accounted for 66-100% of OC, with lower terrigenous (3-8%) and relict (4-16%) contributions. Marine OC in sediments was lower (66-90%), but terrigenous and relict OC were higher (3-17% and 7-13%). Sinking OC is overwhelmingly marine, but pre-aged terrigenous and relict OC are better preserved during delivery to the sediments.
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