SanClements, Michael D听1听;听McKnight, Diane M听2听;听Foreman, Christine M听3
1听INSTAAR, University of Colorado at 麻豆影院
2听INSTAAR, University of Colorado at 麻豆影院
3听Montana State University
While in Antarctica this year I was afforded the opportunity to create a two minute audio postcard for The New York Times website explaining our research and life in Antarctica. This turned out to be very difficult. How do you summarize two years of research and life in Antarctica for a general audience in two minutes? Here is a summary of the project:
Antarctica provides a unique natural environment for the study of dissolved organic matter (DOM). The absence of vascular plants results in an organic carbon pool derived from microbial sources (McKnight et al., 2001). While terrestrial waters in the dry valleys of Antarctica provide valuable insight into the composition of autochthonous organic matter, the Cotton Glacier is a unique system for studying the origins of DOM (Aiken et al., 1996; Foreman et al., In review). The Cotton Glacier fluvial system is extremely dynamic, resulting in little or no accumulation of recalcitrant and humic carbon on a yearly basis, making it ideal for the study of autochthonous DOM precursors.
Throughout the 2009-2010 and 2010-2011 austral summers we sampled the Cotton Glacier Stream ten times. As a comparison, Canada Stream, a terrestrial stream in the McMurdo Dry Valleys was also sampled. Waters from both sites were analyzed for dissolved organic carbon (DOC), base cations, anions, and number of microbiological measurements. Reverse osmosis (RO) was employed to concentrate and isolate DOM from stream waters. UV-VIS and excitation-emission fluorescence spectroscopy were used to infer the composition of DOM in whole waters and RO concentrates.
During the 2010-2011 field season we used a combination of methods to collect data on the hydrology of the supraglacial Cotton Stream. These methods included deployment of a meteorological station, time-lapse photography, satellite imagery, and flow and depth monitoring.
Results from the two field seasons reveal systems with low DOC concentrations, generally ~1 mg L-1 in both Cotton and Canada streams. UV-VIS and fluorescence spectroscopy indicate a unique and transient DOM signature in waters of the Cotton Glacier, while DOM from Canada Stream revealed a more stable refractory organic matter pool. Cotton Glacier waters lacked a humic signature but over time (days) changes in the fluorescence signature demonstrated a shift toward characteristics more commonly found in DOM of other natural waters (i.e., the formation of humic peaks).
Temperature and solar radiation appear to exert significant influence on the daily flow regime but were not the dominant factor in driving extreme changes in hydrology during the summer. Data suggests the flow regimes of supraglacial streams are controlled by a complex relationship between geomorphology and meteorology which may result in a decoupling of flow, temperature, and radiation.
McKnight, D. M., E. W. Boyer, P. K. Westerhoff, P. T. Doran, T. Kulbe, and D. T. Andersen. Limnology and Oceanography, 2001; 46:38-48.
Foreman, C. M., C. E. Morris, R. M. Cory, J. T. Lisle, P. L. Miller, Y.-P. Chin, and D. M. McKnight. Journal of Geophysical Research, In review.
Aiken, G., D. McKnight, R. Harnish, and R. Wershaw. Biogeochemistry, 1996; 34:157-188.