Dissolved Organic Matter (DOM) is a key component of energy and nutrient flux to freshwaters, yet its nature and role in freshwater ecosystems are poorly understood. Recent research suggests that DOM plays an important role in ecosystem function, supporting microbial metabolism, primary production and pollutant transport, and that it acts as a photochemical reactant absorbing sunlight. However, the specific role that DOM plays in any freshwater ecosystem is intimately tied to its specific molecular composition, which in turn reflects the specific environmental character of the waterbody and its catchment.  Much research is currently underway which is now defining the links between the molecular composition and ecological significance of DOM in freshwaters as this varies across biomes and between freshwaters of differing environmental character. This session provides a timely opportunity to bring together the diverse range of disciplines contributing to this effort to share the latest novel approaches, findings and theories.