Dissolved organic material (DOM) in the oceans is 4-6000 years old according to radiocarbon dating, which suggests that this material is environmentally refractory, persisting through multiple cycles of the thermohaline circulation. However, biochemical constituents (e.g. proteins, carbohydrates, and lipids) of ultrafiltered DOM (UDOM) have very different radiocarbon signatures than bulk material, as well as each other. For example, in seawater samples from the deep Pacific Ocean, a quantitatively small lipid fraction (Δ 14C = -709 ‰) was very radiocarbon-depleted compared to carbohydrates (–170 ‰), proteins (-314 ‰), and “acid-insoluble” material (-318 ‰). These results, along with concurrent analyses of depleted lipids in surface waters, suggest a petrogenic source of much of the lipid-like components of UDOM. The other biochemical classes were all approximately “modern” at the surface, indicating creation via photosynthesis. However, carbohydrates at depth had the same radiocarbon content as local, dissolved CO2, while proteins and acid-insoluble material were more depleted. Our results indicate very different cycling rates for these major constituents that are not reflected in analysis of the bulk material.
See more of Compound Specific Analysis and Preparation
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)