Search For The Origins Of Dissolved Organic Matter In A Supraglacial Stream On The Cotton Glacier, Antarctica
SanClements, Michael 1 ; McKnight, Diane 2 ; Chin, Yu-Ping 3 ; Foreman, Christine 4 ; Kilduff, Chip 5
1 INSTAAR, University of Colorado at Boulder
2 INSTAAR, University of Colorado at Boulder
3 Ohio State University
4 Montana State University
5 Rensselear Polytechnic Institute
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 (i.e., extracellular release and leachate from bacteria and algae) (McKnight et al. 2001). While terrestrial waters in the dry valleys of Antarctica provide valuable insight into the composition of autochthonous organic matter, preliminary data from a supraglacial stream on the Cotton Glacier suggests a unique system for studying the origins of DOM (Foreman et al. in review; Aiken et al. 1996). Field observations and data from 2004 suggest the Cotton Glacier fluvial system is extremely dynamic, resulting in little or no accumulation of recalcitrant and humic carbon on a yearly basis (Foreman et al. in review). This lack of refractory organic matter makes it an ideal setting for analyzing the nature of autochthonous DOM precursors. Over the course of the 2009-10 austral summer we sampled the Cotton Glacier Stream four times. As a comparison, Canada Stream, a terrestrial stream in the McMurdo Dry Valleys was also sampled. Waters from both sites were analyzed for total organic carbon (TOC), dissolved organic carbon (DIC), base cations, and anions. 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. Results from the 2004 and 2009-10 field seasons reveal systems with low dissolved organic carbon (DOC) concentrations, generally < 1 mg/L in both Cotton and Canada streams. Reverse osmosis proved a successful technique for the isolation of DOM from low DOC waters. 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). Over the next two years this project aims to answer questions regarding linkages between microbial communities and DOM formation through continued sampling and analysis of Cotton Glacier waters and sediment.
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