DISSOLVED ORGANIC MATTER MOVEMENT ACROSS LAKE SUPERIOR’S TERRESTRIAL-STREAM-COASTAL INTERFACE

Dissolved organic matter (DOM) represents a carbon pool that can be easily translocated between ecosystems with the movement of water. This study examines the controls on DOM quantity and character delivered to Lake Superior primarily during the snowmelt period. We employed long-term stream dissolved organic carbon (DOC) data to determine quantity as well as absorption and fluorescence spectroscopy to analyze DOM structure. Our results indicate that an increasing trend in DOC concentrations, likely driven by decreases in acidity of precipitation, combined with slightly less annual runoff have resulted in relatively constant fluxes of DOM to Lake Superior. Additionally, our study displayed optical changes in DOM translocated from surface litter to deeper mineral soils that changed throughout the progression of snowmelt on different geomorphic aspects, but these changes did not reflect simultaneous pulses of snowmelt at the watershed scale. To aid in future monitoring of DOM translocated to Lake Superior via snowmelt, we developed a relationship between absorbance and dissolved organic carbon concentrations (DOC) for coastal Lake Superior and make recommendations for satellite retrievals of DOM absorbance as a proxy for DOC concentrations