View Abstract

ABIOTIC ALTERATION OF A COMMON BIOCHEMICAL CONFERS SOME OF THE STRUCTURAL COMPLEXITY OBSERVED IN REFRACTORY DISSOLVED ORGANIC MATTER

Identifying mechanisms that store atmospheric CO2 in dissolved organic matter (DOM) on millennial timescales provides insight into how the ocean’s biosphere regulates atmospheric CO2. The long-term accumulation of carbon in the DOM reservoir was conclusively established several decades ago with radiocarbon measurements, but a convincing mechanistic framework for how and why carbon persists as DOM has not been offered. What is lacking is a robust chemical model for at least part of this refractory reservoir. Access to a representative chemical model offers the possibility of identifying sources, sinks and transformation mechanisms. Using comprehensive gas chromatography (GC) we successfully characterized chemical structures in a radiocarbon depleted fraction of marine DOM. We .then linked those structures to a common class of biochemicals using nuclear magnetic resonance (NMR) spectroscopy. The NMR analysis also identified the chemical modifications these biochemicals underwent prior to becoming part of the accumulating DOM reservoir. Based on these findings we conducted laboratory experiments to test our hypothesis regarding the likely precursor biochemicals and formation mechanisms. Results from these experiments confirmed the importance of abiotic processes in generating the vast structural complexity detected in the DOM reservoir and allowed us to directly link compounds accumulating in DOM to their biosynthetic precursors. It is worth noting that lignin oxidation products are the only other component in marine DOM for which biochemical source material has been definitively identified.

Authors

Aluwihare, L. I., Scripps Institution of Oceanography/UCSD, USA, laluwihare@ucsd.edu

Arakawa, N., Scripps Institution of Oceanography/UCSD, USA, narakawa@ucsd.edu

Simpson, A. J., University of Toronto, Canada, andre.simpson@utoronto.ca

Lane, D., University of Toronto, Canada

Soong, R., University of Toronto, Canada

Details

Oral presentation

Session #:012
Date: 02/27/2017
Time: 10:00
Location: 304 A/B

Presentation is given by student: No