Dependency files for r code analysis of "Persistence of Oxygen Dependent Dissolved Organic Matter in Hypoxic Marine Environments"

Low-oxygen marine environments are dynamic hotspots where microbial activity and dissolved organic matter (DOM) cycling are altered, with implications for understanding ecosystem responses to intensifying anthropogenic pressures. The hypoxic barrier hypothesis (HBH) proposed a mechanism by which DOM cycling could be altered by the inhibition of nonrespiratory oxidase enzymes, while respiration continued. To investigate the dependence of DOM composition on oxygen and molecular consequences of the HBH, we performed a set of controlled mesocosm experiments in combination with nontargeted metabolomics to identify classes of compounds that accumulate in hypoxic treatments. Many of these compounds require non-respiratory oxidase enzymes for catabolism in KEGG metabolic maps, and when tested in experiments with microbial communities, their catabolism was inhibited by hypoxia, validating the concept of oxygen dependent dissolved organic matter (ODDOM) that was proposed in the HBH. The identified ODDOM compounds shared chemical features with recalcitrant DOM, such as increased aromaticity, carbon oxidation state, and decreased saturation. Meta-analysis of FT-ICR-MS datasets from three oxygen minimum zones (OMZs) showed that molecules with chemical properties similar to the ODDOM compounds we identified accumulate in oxyclines across diverse OMZs. These findings provide new evidence that oxygen availability directly shapes DOM bioavailability and transformation, with implications for microbial carbon cycling and the production of recalcitrant DOM under expanding hypoxic conditions.