Nutrient cycling in supraglacial environments of the Dark Zone of the Greenland Ice Sheet.

Glaciers and ice sheets host abundant and dynamic communities of microorganisms on the ice surface (supraglacial environments). Recently, it has been shown that Streptophyte ice algae blooming on the surface ice of the south-west coast of the Greenland Ice Sheet are a significant contributor to the 15-year marked decrease in albedo. Currently little is known about the constraints, such as the nutrient cycling, on this large-scale algal bloom. In this study, we present a preliminary data set that investigates the conversion of dissolved inorganic nutrients to the dissolved organic phase occurring in these darkening surface ice environments. Our results show a clear dominance of the organic phase, with 93% of the total dissolved nitrogen and 67% of the total dissolved phosphorus in the organic phase. Correlations between algal abundance and dissolved organic carbon and nitrogen, indicate ice algae are driving the dissolved nutrient phase shift occurring in these supraglacial environments. Dissolved organic nutrient ratios in these supraglacial environments are notably higher than the Redfield Ratio (DON:DOP=49, 78, 116) and DOC:DOP=797, 1166, 2013), suggesting these environments may be phosphorus limited. [ABSTRACT FROM AUTHOR]