Dissolved organic matter (DOM) is a key component of biogeochemical cycles in the ocean and on land. It contains as much carbon as all living biomass on the continents and oceans combined. DOM accumulates in the ocean over several millennia and acts as a substantial carbon storage pool. On the other hand, microbes rely on dissolved molecules for carbon uptake, processing DOM on short time scales. DOM is therefore the main link between organic and inorganic carbon in marine and freshwater ecosystems. A multitude of biogenic and abiotic processes shape the so-called “DOM geometabolome” which parallels sedimentary records as an information-rich set of molecular tracers. These compounds carry the signatures of their source and subsequent journey through the environment. For our session, we invite contributions from all areas of research on DOM biogeochemistry, from empirical to modelling studies, from groundwaters and lakes across the freshwater-to-marine continuum. Molecular-level and interdisciplinary studies including modeling approaches are particularly welcome. Also, contributions that apply innovative analytical approaches, or identify novel concepts, fundamental challenges and the future directions of this fast-growing field of research are encouraged.