We evaluate how the presence of a lake within stream networks regulates DOC dynamics.  We hypothesize that lakes act as a buffer to snowmelt DOC flushing in outflow streams, as well as act as a source of high quality DOC to outflow streams.  We tested these hypotheses by 1) weekly measurements of DOC quantity and quality in Bull Trout Lake inflow and outflow over a 6-month time period and 2) incubating streamwater in the presence and absence of UV light and microbial communities to evaluate controls on DOC quality over time.  Both inflow and outflow DOC concentrations peaked in late May.  Flushing (i.e. linear declines in DOC) was evaluated as ln[DOC] from 22-May to 20-July.  Inflow DOC recession was 2.5X faster than the outflow, indicating lake buffering of snowmelt DOC flushing.  DOC quality was measured by specific UV absorbance (SUVA, 254nm).  SUVA values peaked (lowest quality) in early June, indicating a prolonged flushing of aromatic terrestrial DOC.  Results of the incubation experiment indicate that DOC quality significantly increased in the presence of UV light and microbial communities.  Together, our results suggest that lakes alter the timing and character of DOC export to downstream locations via abiotic and biotic processes.