Streams draining urban and agriculture catchments are often a source of inorganic nutrients to downstream aquatic ecosystems, but little is known about how changes in land use influence the quality and biodegradability of dissolved organic matter (DOM). We used parallel factor analysis of excitation-emission fluorescence spectroscopy and biodegradation incubations to examine how DOM composition influences bioavailable dissolved organic carbon (DOC) in surface waters of urban and agricultural catchments during summer (low flow), winter (high flow) and spring (flow recession). Percent bioavailable DOC was variable for all catchments (2-57%) and negatively related to percent humic-like fluorescence, but positively related to percent protein-like fluorescence and simple fluorescence metrics of DOM precursor material (fluorescence index and beta:alpha values). Conversely, highly variable DOC concentrations (2-140 mg L-1) were negatively related to protein-like fluorescence and positively related to humic-like fluorescence. Elevated concentrations of DOC (>30 mg L-1) in agro-urban streams revealed fluorescence indices (