The Hydroecology of an Ephemeral Wetland in the McMurdo Dry Valleys, Antarctica. Issue 12 (14th December 2019)

• Record Type: Journal Article
• Authors: Wlostowski, Adam N.; Schulte, Nicholas O.; Adams, Byron J.; Ball, Becky A.; Esposito, Rhea M.M.; Gooseff, Michael N.; Lyons, W.Berry.; Nielsen, Uffe N.; Virginia, Ross A.; Wall, Diana H.; Welch, Kathy A.; McKnight, Diane M.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 12(2019)
• Page Start: 3814
• Page End: 3830
• Publication Date: 2019-12-14
• Subjects: Antarctica -- desert hydrology -- diatom biodiversity -- hyporheic interactions -- wetlands; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2019JG005153
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: The McMurdo Dry Valleys is a polar desert on the coast of East Antarctica where ephemeral wetlands become hydrologically active during warm and sunny summers when subsurface flows are generated from melting snowfields. To understand the structure and function of polar wetland ecosystems, we investigated the hydroecology of one such wetland, the Wormherder Creek wetland, during the warm and sunny summer of 2008 – 2009, when the wetland was hydrologically reactivated. Conservative tracer (LiCl) was injected for a 2‐hr period into a stream above the wetland to determine flow path orientations and hydrologic residence times. Tracer results indicated that surface water is rapidly exchanged with wetland groundwater and wetland residence times may exceed two austral summers. Major ion concentrations were uniform in samples from surface water and shallow groundwater throughout the wetland. Microbial mats in the wetland had high autotrophic index values (the ratios of chlorophyll a [Chl‐a]/ash‐free dry mass), ranging from 9 to 38 μg Chl‐a/mg ash‐free dry mass, indicative of actively photosynthesizing mat communities. The diatom communities in the mats were relatively uniform compared to those in mats from regularly flowing McMurdo Dry Valleys streams, with four endemic and one widespread diatom taxa of the genus Luticola accounting for an average of 86% of the community. These results indicate that the hydrologic characteristics of the wetland contribute to uniform geochemical conditions. In turn, uniform geochemical conditions may explain the high autotrophic index values of the microbial mats and relatively low spatial variation of the diatom community. Key Points: Experimental tracer addition in an Antarctic wetland reveals substantial mixing between stream waters and groundwaters Hydrologic retention in the wetland likely exceeds two austral seasons Wetland hydrologic characteristics sustain spatially homogeneous geochemical conditions and stream microbial mat characteristics