This project will conduct laboratory and field investigations into the molecular-level transformations in the macromolecular component of dissolved organic matter in seawater that are caused by photooxidative processes. The hypotheses to be tested in the research are: 1) that photooxidation represents a major process for remineralization of both allochthonous and autochthonous DOC in the ocean; 2) that terrestrial (riverine) DOC, especially its lignin component, is preferentially destroyed by photooxidation in comparison to marine DOC; 3) that photoprocesses in the ocean are predominately destructive, not constructive, to DOC; 4) that these photooxidative processes impart a unique molecular level signature on DOC that can be distinguished by Pyrolysis-GC-MS. The approach will be to examine the relative rates of photooxidation and macromolecular oxidation products of "endmember" sources of DOC in laboratory experiments and simultaneously determine the distributions of reactive starting materials and photooxidation products in areas of the ocean where natural gradients can be expected. Examining oceanic processes affecting DOC at the molecular level is fundamental to understanding the transport and fats of material, particularly carbon, in the marine environment. Thus, this research is addressing an aspect of current concerns relating to climate, a present problem of planetary significance.
