Changes in Dissolved Organic Matter (DOM) Fluorescence in Proglacial Antarctic Streams

Dissolved organic matter (DOM) exported in glacier meltwater influences downstream biogeochemical processes, and climate warming may increase the meltwater DOM flux. In this study, we quantify and use fluorescence spectroscopy and parallel factor analysis (PARAFAC) to characterize DOM exported in glacier meltwater in Taylor and Wright Valleys, McMurdo Dry Valleys, Antarctica. Andersen Creek, a proglacial stream draining Canada Glacier meltwater, exported similar to 20 kg of DOM as dissolved organic carbon (DOC) to Lake Hoare during the melt season. Supraglacial snowpack DOM from all of the Dry Valley glaciers sampled exhibits "protein-like" fluorescence indicating that it contains potentially labile moieties that might be a favorable substrate supporting downstream microbial metabolism. However, this protein-like fluorescence does not persist in any of the meltwater streams surveyed, suggesting that it is quickly transformed by resident microbial populations and/or mixed with other DOM pools within stream channels or along its margins. Given the seemingly ubiquitous protein-like fluorescent characteristic of glacier-derived DOM and the immediate change to the bulk DOM in glacier streams, a more thorough characterization of the bulk DOM pool from glacial sources and through downstream ecosystems would yield valuable information about the potential contribution of glacier melt to the global carbon cycle.