Glacial Meltwater Streams of the McMurdo Dry Valleys, Antarctica: Ecosystems Waiting for Water

Details Glacial Meltwater Streams of the McMurdo Dry Valleys, Antarctica: Ecosystems Waiting for Water Glacial Meltwater Streams of the McMurdo Dry Valleys, Antarctica: Ecosystems Waiting for Water

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.p22a..06m&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #P22A-06

Mathematics

Logic

5419 Hydrology And Fluvial Processes

Scientific paper

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, evident as a damp area underneath and adjacent to the stream. The lower boundary of the hyporheic zone is determined by the depth to permafrost. On sunny days, stream temperatures can reach 15 °C, and advection of this warm water can erode the frozen lower boundary of the hyporheic zone. In cold summers, streamflow is fed mostly by melt from the faces of the source glaciers and a large portion of this meltwater may be stored in the hyporheic zone and then lost through sublimation, rather than discharged to the lakes. Some streams have thriving microbial mats composed of cyanobacteria and diatoms. These mats are freeze-dried through the winter and begin photosynthesizing with the onset of flow. To evaluate the longer term persistence of cynaobacterial mats, we diverted flow to an abandoned channel, which had not received substantial flow for approximately two decades. 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. 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 stream ecosystems to climatic and geomorphological change.

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