Tracking cupric oxide-derived compounds across high and low latitude oceans

The majority of terrigenous dissolved organic matter is efficiently mineralized in ocean margins, but some terrigenous materials are highly resistant to decomposition and contribute to the reservoir of slowly cycling components of the marine carbon cycle. Here we expand the focus of cupric oxide oxidation products to include 26 identified and 150 structurally related compounds to create a more powerful tool for tracking terrigenous dissolved organic matter across the Gulf of Mexico, the mid-Atlantic Bight, and the Arctic Ocean. Water samples were extracted with reversed-phase sorbents, digested with cupric oxide, and analyzed by gas chromatography mass spectrometry in full scan mode. Chromatograms and mass spectral data were processed with automated software routines to extract and quantify cupric oxide-derived compounds and generate molecular networks to identify similar core structures among them. The expanded suite of compounds includes substituted aromatic carboxylic acids, aldehydes, ketones, and many structurally related compounds. Substituted aromatic carboxylic acids were up to 10-fold more abundant than lignin phenols, suggesting these compounds constitute an important fraction of chromophoric dissolved organic matter. Preliminary quantification of the expanded suite of CuO-derived compounds indicates distinct regional patterns and holds the potential to decipher complexities within terrestrial and marine dissolved organic matter degradation.