@article {3721, title = { Long-Term Hydrologic Control of Microbial Mat Abundance in McMurdo Dry Valley Streams, Antarctica.}, journal = {Ecosystems}, volume = {18}, year = {2015}, month = {03/2015}, pages = {310-327}, chapter = {310}, abstract = {

Given alterations in global hydrologic regime, we examine the role of hydrology in regulating stream microbial mat abundance in the McMurdo Dry Valleys, Antarctica. Here, perennial mats persist as a desiccated crust until revived by summer streamflow, which varies inter-annually, and has increased since the 1990s. We predicted high flows to scour mats, and intra-seasonal drying to slow growth. Responses were hypothesized to differ based on mat location within streams, along with geomorphology, which may promote (high coverage) or discourage (low coverage) accrual. We compared hydrologic trends with the biomass of green and orange mats, which grow in the channel, and black mats growing at stream margins for 16 diverse stream transects over two decades. We found mat biomass collectively decreased during first decade coinciding with low flows, and increased following elevated discharges. Green mat biomass showed the greatest correlations with hydrology and was stimulated by discharge in high coverage transects, but negatively correlated in low coverage due to habitat scour. In contrast, orange mat biomass was negatively related to flow in high coverage transects, but positively correlated in low coverage because of side-channel expansion. Black mats were weakly correlated with all hydrologic variables regardless of coverage. Lastly, model selection indicated the best combination of predictive hydrologic variables for biomass differed between mat types, but also high and low coverage transects. These results demonstrate the importance of geomorphology and species composition to modeling primary production, and will be useful in predicting ecological responses of benthic habitats to altered hydrologic regimes.

}, keywords = {LTER-MCM}, url = {http://link.springer.com/article/10.1007\%2Fs10021-014-9829-6}, author = {Tyler J. Kohler and Lee F. Stanish and Stenven Crisp and Koch, J. and Liptzin, D. and Baeseman, J. and Diane M. McKnight} } @article {3222, title = {A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond}, journal = {Antarctic Science}, volume = {27}, year = {2015}, month = {Jan-02-2015}, pages = {3 - 18}, abstract = {

Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to \‘scan the horizon\’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone

}, keywords = {LTER-MCM}, issn = {0954-1020}, doi = {10.1017/S0954102014000674}, url = {http://www.journals.cambridge.org/abstract_S0954102014000674}, author = {Kennicutt, M.C. and Steven L. Chown and Cassano, J.J. and Liggett, D. and Lloyd S. Peck and Massom, R. and Rintoul, S.R. and Storey, J. and Vaughan, D.G. and Wilson, T.J. and Allison, I. and Ayton, J. and Badhe, R. and Baeseman, J. and Barrett, P.J. and Elanor R. Bell and Bertler, N. and Bo, S. and Brandt, A. and David Bromwich and Craig S Cary and Clark, M.S. and Peter Convey and Costa, E.S. and Cowan, D. and Deconto, R. and Dunbar, R. and Elfring, C. and Escutia, C. and Francis, J. and Fricker, H.A. and Fukuchi, M. and Gilbert, N. and Gutt, J. and Havermans, C. and Hik, D. and Hosie, G. and Jones, C. and Kim, Y.D. and Le Maho, Y. and Lee, S.H. and Leppe, M. and Leitchenkov, G. and Li, X. and Lipenkov, V. and Lochte, K. and L{\'o}pez-Mart{\'\i}nez, J. and {\"u}decke, C. and W. Berry Lyons and Marenssi, S. and Miller, H. and Morozova, P. and Naish, T. and Nayak, S. and Ravindra, R. and Retamales, J. and Ricci, C.A. and Rogan-Finnemore, M. and Ropert-Coudert, Y. and Samah, A.A. and Sanson, L. and Scambos, T. and I.R. Schloss and Shiraishi, K. and Siegert, M.J. and Sim{\~o}es, J.C. and Storey, B. and Sparrow, M.D. and Diana H. Wall and Walsh, J.C. and Wilson, G. and Winther, J.G. and J.C. Xavier and Yang, H. and Sutherland, W.J.} } @inbook {1168, title = {Antarctic McMurdo Dry Valley stream ecosystems as analog to fluvial systems on Mars}, booktitle = {Life in Antarctic Deserts and other Cold Dry Environments}, year = {2010}, pages = {139 - 159}, publisher = {Cambridge University Press}, organization = {Cambridge University Press}, address = {Cambridge}, keywords = {LTER-MCM}, isbn = {9780521889193}, doi = {10.1017/CBO9780511712258.005}, author = {Michael N. Gooseff and Diane M. McKnight and Carr, M. H. and Baeseman, J.}, editor = {Peter T. Doran and W. Berry Lyons and Diane M. McKnight} } @article {4816, title = {Effect of unsteady flow on nitrate loss in an oligotrophic, glacial meltwater stream}, journal = {Journal of Geophysical Research}, volume = {115}, year = {2010}, month = {03/2010}, pages = {G01001}, abstract = {

The McMurdo Dry Valleys of Antarctica are among the coldest, driest ecosystems on Earth. During the austral summer, glacial meltwater supports cyanobacterial mat communities in some streams, but they are not ubiquitous. We conducted a nitrate (NO3-) enrichment tracer injection in Huey Creek to quantify NO3- loss in a Dry Valley stream where algal mats would not obscure hyporheic microbial processes. Unsteady streamflow led to diel variability in the tracer concentration and in surface/subsurface water and solute exchange. Subsequently, concentrations of NO3-, nitrite (NO2-), ammonium (NH4+), and dissolved organic carbon (DOC) varied significantly during the injection, with a net loss of NO3-, NO2-, and DOC, and production of nitrous oxide. These mass changes within a reach were often coincident with high streamflows. Reactivity also coincided with the highest DOC concentrations, suggesting that DOC is the primary limitation to heterotrophic microbial activity in the stream. Together, streamflow and DOC availability create the hot spots and hot moments that dominate NO3- reactivity and removal in this polar desert ecosystem. The combination of spatially and temporally variable hyporheic dynamics and solute availability underscore the limitations of common nutrient uptake metrics and transient storage models when unsteady flow conditions exist.

}, keywords = {LTER-MCM, Antarctica, hot spots/hot moments, hyporheic exchange, nitrogen cycling, unsteady flow}, doi = {10.1029/2009JG001030}, url = {http://doi.wiley.com/10.1029/2009JG001030}, author = {Koch, J. and Diane M. McKnight and Baeseman, J.} }