oa Significant Spatiotemporal Variations in the Dissolved Metabolomes Across the Yangtze River Estuary and East China Sea

The molecular composition and properties of Dissolved Organic Matter (DOM) are crucial for understanding biogeochemical cycling in marine ecosystems. Metabolomics, as a cutting-edge technique, seeks to elucidate the core microbial metabolomes driven by environmental stressors. Utilizing untargeted Liquid Chromatography-Mass Spectrometry (LC-MS) based metabolomics, we investigate how hydrological processes, marked by rapid fluctuations in physicochemical properties, influence metabolome composition within high-resolution vertical and horizontal frontal structures in the Yangtze River Estuary and East China Sea. Our findings reveal significant temporal and spatial variations in the dissolved metabolomes within these frontal zones across tidal cycles, vertical stratification, and seasonal transitions in the Yangtze River Estuary. Notably, anthropogenic organic substrates exhibited substantial spatial variability, influenced by hydrodynamic factors. The metabolomic analysis thus offers novel insights into the differential fates of exogenous versus endogenous organic compounds, enhancing our understanding of the respective contributions of anthropogenic and natural products to the DOM pool.