Background: The range of sites within the LTER network provides an excellent opportunity to understand aquatic and soil OM (organic matter) dynamics in diverse ecosystems in order to develop overarching hypotheses about OM dynamics on a larger scale in the context of the global carbon cycle. Dissolved organic material (DOM) is a major pool of organic carbon in all aquatic ecosystems, has high concentrations in soil interstitial water, and can be transported from soils into aquatic ecosystems. DOM represents both a substrate for microbial growth and an important characteristic of aquatic and soil environments, regulating light penetration in lakes and streams and the bioavailability of trace metals, for example. Diverse studies have shown that the chemical properties of DOM reflect the predominant sources. In lakes and streams, DOM can originate from the surrounding watershed, specifically the soluble portion of the soil organic matter (SOM) and from production of DOM within the aquatic ecosystem. Within the LTER network, understanding the dynamic processes controlling DOM fluxes and reactivity has been advanced through application of modern spectroscopic methods for chemical characterization in monitoring programs and shorter term studies. Analysis of DOM from many LTER sites conducted during the LTER 2004 workshop on this topic (…) revealed the broad range in DOM quality that occurs across the LTER network and among ecosystems of a given LTER site. The results were published, Jaffe et al. 2008. Spatial and temporal variations in DOM composition in ecosystems: The importance of long-term monitoring of optical properties. Journal of Geophysical Research-Biogeosciences 113 G4 G04032), which has now been cited 50 times.