Characterization of a rarely studied ecosystem: Initial insights into the functioning of Antarctic supraglacial streams

Glacial ecosystems are biogeochemically active environments that influence downstream ecosystem function, yet there are few studies describing supraglacial stream systems, especially in Antarctica. During the 2009-2010 and 2010-2011 austral summers we sampled the supraglacial Cotton Glacier Stream at regular intervals to characterize one of these rarely studied systems. Throughout the 2009-2010 summer we focused on stream chemistry and dissolved organic matter (DOM) characterization. During the 2010-2011 season we established a meteorological station on the glacial surface to conduct measurements of the physical environment. Meteorological data revealed that during summer, temperatures do not frequently exceed zero Celsius for extended periods of time. Pressure transducers and time lapse cameras were installed to capture changes in water depth and revealed a system capable of extreme change on the time-scale of hours. While both temperature and solar radiation appeared to exert significant influence on the daily flow regime, they were not the dominant factor in driving extreme changes in hydrology during the summer. Our observations indicate that extreme hydrologic events (i.e. rapid flooding and draining), were largely controlled by downstream moulins which dictate the drainage of Cotton Stream. This suggests the flow regimes of large Antarctic supraglacial streams may be controlled by a complex relationship between geomorphology and meteorology; resulting in a decoupling of flow, temperature and solar radiation. Chemical analysis and DOM characterization indicate that the dynamic nature of Cotton Stream, paired with very dilute nutrient concentrations, results in an ecosystem with little to no legacy of microbial communities and DOM from year to year.