Abundance and Dynamics of Dissolved Organic Carbon in Glacier Systems
J. D. Barker, M. J. Sharp, S. J. Fitzsimons, R. J. Turner
The biogeochemical cycling of organic carbon (OC) has important implications for aquatic system ecology because the abundance and molecular characteristics of OC influence contaminant transport and bioavailability, and determine its suitability as a substrate for microbial metabolism. There have been few studies of OC cycling in glacier systems and questions remain regarding the abundance, provenance, and biogeochemical transformations of OC in these environments. To address these questions, the abundance and fluorescence characteristics of dissolved organic carbon (DOC) were investigated at John Evans Glacier and Outre Glacier, Canada, and Victoria Upper Glacier, Antarctica. These systems are characterized by different thermal and hydrological regimes, and have different potential DOC sources. Where possible, samples of supraglacial runoff, glacier ice and basal ice, and subglacial meltwater were collected. The DOC concentration in each sample was measured (high-temperature combustion and non-dispersive IR detection), and emission and/or synchronous fluorescence spectroscopy were used to characterize the DOC from each environment. DOC exists in detectable quantities (0.06–46.6 ppm) in all of these glacier systems. The fluorescence characteristics of DOC vary between glaciers, between environments at the same glacier, and over time within a single environment. These results suggest that quality of available OC and glacier hydrological flow routing influence the characteristics of DOC, and that microbial cycling of OC may be active in glacier systems.