@article {5015, title = {Morphology and distribution of bubble-supported microbial mats from ice-covered Antarctic lakes}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {130}, year = {2025}, month = {03/2025}, abstract = {

Gas bubbles directly influence the macromorphology of benthic microbial mats resulting in preservable biosedimentary structures. This study characterizes the morphology and distribution of microbial mats growing in gas-supersaturated, perennially ice-covered lakes Fryxell, Joyce, and Hoare of the McMurdo Dry Valleys of Antarctica. Photosynthetic benthic mats within the gas-supersaturated zone trap oxygen-rich bubbles and become buoyant, tearing off the bottom as \“liftoff mats.\” These liftoff mats form a succession of morphologies starting with bubble-induced deformation of flat mats into tent, ridge, and finger liftoff mat. With progressive deformation, mats tear, forming sheet liftoff, while multiple cycles of deformation and tearing transform sheet into strip liftoff. Some mats detach from the substrate and float to the underside of the ice. The depth range of the liftoff zone has varied over time at each lake. Downslope expansion of bubble formation brings previously bubble-free, deep-water pinnacle mats into the liftoff zone. When the liftoff zone shallows, liftoff mats at the deeper end deflate and can become scaffolding for additional mat growth. The superposition and relative orientation of liftoff and pinnacle mats can be used to track the maximum depth of the liftoff zone and changes in gas saturation state in these lakes through time. Our results demonstrate that gas bubbles, even when they are transitory, can exert a significant impact on the morphology of microbial mats at larger scales. This provides a way to identify similar structures and gas supersaturated environments in the biosedimentary record.

}, keywords = {LTER-MCM, Antarctica, biosediments, bubble-driven morphology, gas-supersaturation, ice-covered lakes, microbial mats}, issn = {2169-8953}, doi = {10.1029/2024JG008516}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JG008516}, author = {Juarez-Rivera, M. and Mackey, Tyler J. and Ian Hawes and Sumner, Dawn Y.} } @article {4940, title = {McMurdo Dry Valley lake edge {\textquoteleft}moats{\textquoteright}: The ecological intersection between terrestrial and aquatic polar desert habitat}, journal = {Antarctic Science}, year = {2024}, month = {04/2024}, pages = {1 - 17}, abstract = {

Aquatic ecosystems - lakes, ponds and streams - are hotspots of biodiversity in the cold and arid environment of Continental Antarctica. Environmental change is expected to increasingly alter Antarctic aquatic ecosystems and modify the physical characteristics and interactions within the habitats that they support. Here, we describe physical and biological features of the peripheral \‘moat\’ of a closed-basin Antarctic lake. These moats mediate connectivity amongst streams, lake and soils. We highlight the cyclical moat transition from a frozen winter state to an active open-water summer system, through refreeze as winter returns. Summer melting begins at the lakebed, initially creating an ice-constrained lens of liquid water in November, which swiftly progresses upwards, creating open water in December. Conversely, freezing progresses slowly from the water surface downwards, with water at 1 m bottom depth remaining liquid until May. Moats support productive, diverse benthic communities that are taxonomically distinct from those under the adjacent permanent lake ice. We show how ion ratios suggest that summer exchange occurs amongst moats, streams, soils and sub-ice lake water, perhaps facilitated by within-moat density-driven convection. Moats occupy a small but dynamic area of lake habitat, are disproportionately affected by recent lake-level rises and may thus be particularly vulnerable to hydrological change.

}, keywords = {LTER-MCM, connectivity, ecosystem, ice, microbial mats, transition}, issn = {0954-1020}, doi = {10.1017/S0954102024000087}, url = {https://www.cambridge.org/core/journals/antarctic-science/article/mcmurdo-dry-valley-lake-edge-moats-the-ecological-intersection-between-terrestrial-and-aquatic-polar-desert-habitats/31D94DD51E651603482A3AE6E8A52A57}, author = {Stone, Michael S. and Devlin, Shawn and Ian Hawes and Kathleen A. Welch and Michael N. Gooseff and Cristina D. Takacs-Vesbach and Rachael M. Morgan-Kiss and Byron Adams and John E. Barrett and John C. Priscu and Peter T. Doran} } @article {4732, title = {The magnitude and climate sensitivity of isotopic fractionation from ablation of Antarctic Dry Valley lakes}, journal = {Arctic, Antarctic, and Alpine Research}, volume = {53}, year = {2021}, month = {12/2021}, pages = {352 - 371}, abstract = {

There has been extensive research on the effects of evaporation on the isotopic ratio of lacustrine and marine water bodies; however, there are limited data on how ablation or sublimation from lake or sea ice influences the isotopic ratio of the residual water body. This is a challenging problem because there remains uncertainty on the magnitude of fractionation during sublimation and because ablation can involve mixed-phase processes associated with simultaneous sublimation, melting, evaporation, and refreezing. This uncertainty limits the ability to draw quantitative inferences on changing hydrological budgets from stable isotope records in arctic, Antarctic, and alpine lakes. Here, we use in situ measurements of the isotopic ratio of water vapor along with the gradient diffusion method to constrain the isotopic ratio of the ablating ice from two lakes in the McMurdo Dry Valleys, Antarctica. We find that during austral summer, the isotopic fractionation of ablation was insignificant during periods of boundary layer instability that are typical during midday when latent heat is highest. This implies that the loss of mass during these periods did not yield any isotopic enrichment to the residual lake mass. However, fractionation increased after midday when the boundary layer stabilized and the latent heat flux was small. This diurnal pattern was mirrored on synoptic timescales, when following warm and stable conditions latent heat flux was low and dominated by higher fractionation for a few days. We hypothesize that the shifting from negligible to large isotopic fractionation reflects the development and subsequent exhaustion of liquid water on the surface. The results illustrate the complex and nonlinear controls on isotopic fractionation from icy lakes, which implies that the isotopic enrichment from ablation could vary significantly over timescales relevant for changing lake volumes. Future work using water isotope fluxes for longer periods of time and over additional perennial and seasonal ice-covered lake systems is critical for developing models of the isotopic mass balance of arctic and Antarctic lake systems.

}, keywords = {LTER-MCM, Dry Valley lakes, isotope fractionation, stable water isotopes}, issn = {1523-0430}, doi = {10.1080/15230430.2021.2001899}, url = {https://www.tandfonline.com/doi/full/10.1080/15230430.2021.2001899}, author = {Bellagamba, Anthony W. and Berkelhammer, Max and Winslow, Luke A. and Peter T. Doran and Myers, Krista F. and Devlin, Shawn and Ian Hawes} } @article {4837, title = {Meteorological connectivity from regions of high biodiversity within the McMurdo Dry Valleys of Antarctica}, journal = {Journal of Applied Meteorology and Climatology}, volume = {58}, year = {2019}, month = {11/2019}, pages = {2437 - 2452}, abstract = {

Meteorological connectivity between biological hot spots of the McMurdo Dry Valleys (MDVs) of Antarctica is thought to play a role in species distribution and abundance through the aeolian transport of bioaerosols. Understanding the potential role of such meteorological connectivity requires an understanding of near-surface wind flow within and between valley airsheds. To address this, we applied Lagrangian wind trajectory modeling to mesoscale (spatial resolution of ~1 km) weather model output to predict connectivity pathways, focusing on regions of high biodiversity. Our models produce maps of a likelihood metric of wind connectivity that demonstrate the synoptic and mesoscale dependence of connections between local, near-local, and nonlocal areas on wind transport, modulated by synoptic weather and topographic forcing. These connectivity areas can have spatial trends modulated by the synoptic weather patterns and locally induced topographically forced winds. This method is transferrable to other regions of Antarctica for broader terrestrial, coastal, and offshore ecological connectivity research. Also, our analysis and methods can inform better placement of aeolian dust and bioaerosol samplers in the McMurdo Dry Valleys, provide preliminary guidelines behind the meteorological controls of sediment transport and smaller particle distribution, and present quantifiable knowledge informing new hypotheses around the potential of wind acting as a physical driver for biological connectivity in the MDVs.

}, keywords = {LTER-MCM, Antarctica, atmosphere, biosphere-atmosphere interaction, mesoscale models, mesoscale processes, numerical analysis/modeling}, issn = {1558-8424}, doi = {10.1175/JAMC-D-18-0336.1}, url = {https://journals.ametsoc.org/view/journals/apme/58/11/jamc-d-18-0336.1.xml}, author = {Katurji, Marwan and Khan, Basit and Sprenger, Michael A. and Datta, Rajasweta and Joy, Kurt and Zawar-Reza, Peyman and Ian Hawes} } @article {3710, title = {Microbial Mat Communities along an Oxygen Gradient in a Perennially Ice-Covered Antarctic Lake}, journal = {Applied and Environmental Microbiology}, volume = {82}, year = {2016}, month = {01/2016}, pages = {620 - 630}, keywords = {LTER-MCM}, issn = {0099-2240}, doi = {10.1128/AEM.02699-15}, url = {http://aem.asm.org/lookup/doi/10.1128/AEM.02699-15}, author = {Jungblut, Anne D. and Ian Hawes and Mackey, Tyler J. and Krusor, Megan and Peter T. Doran and Sumner, Dawn Y. and Eisen, Jonathan A. and Hillman, Colin and Goroncy, Alexander K.}, editor = {Stams, A. J.} } @article {1466, title = {McMurdo LTER: Photosynthesis in an extreme shade habitat: benthic microbial mats from Lake Hoare, Antarctica}, journal = {Journal of Phycology}, volume = {35}, year = {1999}, pages = {448-459}, keywords = {LTER-MCM}, author = {Ian Hawes and Anne-Maree Schwarz} } @inbook {1559, title = {The microbial loop in Antarctic lakes}, booktitle = {Ecosystem Processes in Antarctic Ice-free Landscapes}, year = {1997}, pages = {231-240}, publisher = {Balkema Press}, organization = {Balkema Press}, address = {Rotterdam}, keywords = {LTER-MCM}, author = {Johanna Laybourn-Parry} } @article {1591, title = {McMurdo LTER: Photosynthesis in benthic cyanobacterial mats from Lake Hoare, Antarctica}, journal = {Antarctic Journal of the U.S.}, volume = {30}, year = {1995}, pages = {296-297}, keywords = {LTER-MCM}, author = {Ian Hawes and Anne-Maree Schwarz} }