부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.geomorph.2006.07.025 Byline: D.M. McKnight (a), C.M. Tate (b), E.D. Andrews (b), D.K. Niyogi (c), K. Cozzetto (a), K. Welch (d), W.B. Lyons (d), D.G. Capone (e) Keywords: Glacial meltwater streams; Abandoned channel; Stream ecosystems; Cyanobacterial mat; McMurdo Dry Valleys; Antarctica Abstract: The McMurdo Dry Valleys of Antarctica contain many glacial meltwater streams that flow for 6 to 12 weeks during the austral summer and link the glaciers to the lakes on the valley floors. Dry valley streams gain solutes longitudinally through weathering reactions and microbial processes occurring in the hyporheic zone. Some streams have thriving cyanobacterial mats. In streams with regular summer flow, the mats are freeze-dried through the winter and begin photosynthesizing with the onset of flow. To evaluate the longer term persistence of cyanobacterial mats, we diverted flow to an abandoned channel, which had not received substantial flow for approximately two decades. Monitoring of specific conductance showed that for the first 3 years after the diversion, the solute concentrations were greater in the reactivated channel than in most other dry valley streams. We observed that cyanobacterial mats became abundant in the reactivated channel within a week, indicating that the mats had been preserved in a cryptobiotic state in the channel. Over the next several years, these mats had high rates of productivity and nitrogen fixation compared to mats from other streams. Experiments in which mats from the reactivated channel and another stream were incubated in water from both of the streams indicated that the greater solute concentrations in the reactivated channel stimulated net primary productivity of mats from both streams. These stream-scale experimental results indicate that the cryptobiotic preservation of cyanobacterial mats in abandoned channels in the dry valleys allows for rapid response of these stream ecosystems to climatic and geomorphological change, similar to other arid zone stream ecosystems. Author Affiliation: (a) Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA (b) Water Resources Division, U.S. Geological Survey, Denver, CO 80303 80225, USA (c) Biological Sciences, University of Missouri-Rolla, Rolla, MO 65409, USA (d) Byrd Polar Research Center, Ohio State University, Columbus, OH 43210, USA (e) Wrigley Institute for Environmental Studies, University of Southern California, Los Angeles, CA 90089, USA Article History: Received 15 January 2005; Revised 27 July 2006; Accepted 27 July 2006