Sinking particulate organic carbon (POC) is the major mechanism which effectively removes carbon from the ocean's upper water column. This “biological pump” is the source of all carbon that eventually reaches the ocean floor. Less than one percent of carbon produced at the ocean surface is ultimately preserved in ocean sediments. A major gap in our understanding of the oceanic carbon cycling is that while nearly all POM can be identified at the surface, in the deep ocean, more than 70% is molecularly uncharacterized. Recent studies comparing radiocarbon isotopic signatures between the major compound classes (amino acids, carbohydrates and lipids) have suggested that MUC from the deep Northeast Pacific is comprised mostly of lipid-like macromolecules. In contrast, NMR results from the western Arabian Sea and equatorial Pacific Ocean conflict with this view, suggesting that lipid materials are most rapidly degraded, and MUC is instead dominated by amino acids. Together, these results suggest that MUC composition might vary greatly depending on oceanic regimes. To test this hypothesis, stable and radiocarbon isotopes were measured from sediment trap samples analyzed from two contrasting environments, the Cariaco Basin (CAR, off the coast of Venezuela in the Atlantic, 1400 m deep) and Santa Barbara Basin (SBB, off Southern California, 600 m deep). Samples were collected at depths of 275-m and 1255-m from Nov 1998 – Oct 1999, in the Cariaco as part of the CARIACO project and at 450-m from April 1999 – March 2000 in Santa Barbara as part of the University of South Carolina - Marine Sediments Research Laboratory. Samples were chosen from yearly time series for each location in order to account for seasonal changes in sources and composition. Sediment trap material was separated into main biochemical classes and MUC using previously described methods (X.-C. Wang et al. 1998). The d13C and Δ14C values were measured for bulk material and for each individual fraction. The acid-insoluble signature is compared to the major compound classes for insight into main biochemical precursors to MUC in each environment. Initial results suggest different biochemical classes dominate MUC in preserved organic carbon in these contrasting oceanic regimes.
See more of Poster Session I
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)