@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 {4690, title = {Meta-analysis of Cryogenian through modern quartz microtextures reveals sediment transport histories}, journal = {Journal of Sedimentary Research}, volume = {91}, year = {2021}, month = {09/2021}, pages = {929-944}, abstract = {

Quantitative analysis of quartz microtextures by means of scanning electron microscopy (SEM) can reveal the transport histories of modern and ancient sediments. However, because workers identify and count microtextures differently, it is difficult to directly compare quantitative microtextural data analyzed by different workers. As a result, the defining microtextures of certain transport modes and their probabilities of occurrence are not well constrained. We used principal-component analysis (PCA) to directly compare modern and ancient aeolian, fluvial, and glacial samples from the literature with nine new samples from active aeolian and glacial environments. Our results demonstrate that PCA can group microtextural samples by transport mode and differentiate between aeolian transport and fluvial and glacial transport across studies. The PCA ordination indicates that aeolian samples are distinct from fluvial and glacial samples, which are in turn difficult to disambiguate from each other. Ancient and modern sediments are also shown to have quantitatively similar microtextural relationships. Therefore, PCA may be a useful tool to constrain the ambiguous transport histories of some ancient sediment grains. As a case study, we analyzed two samples with ambiguous transport histories from the Cryogenian Br{\r a}vika Member (Svalbard). Integrating PCA with field observations, we find evidence that the Br{\r a}vika Member facies investigated here includes aeolian deposition and may be analogous to syn-glacial Marinoan aeolian units including the Bakoye Formation in Mali and the Whyalla Sandstone in South Australia.

}, keywords = {LTER-MCM}, issn = {1527-1404}, doi = {10.2110/jsr.2020.151}, url = {https://pubs.geoscienceworld.org/jsedres/article/91/9/929/607764/Meta-analysis-of-Cryogenian-through-modern-quartz}, author = {Reahl, Jocelyn N. and Cantine, Marjorie D. and Wilcots, Julia and Mackey, Tyler J. and Bergmann, Kristin D.} } @article {4597, title = {Metabolic capacity of the Antarctic cyanobacterium Phormidium pseudopriestleyi that sustains oxygenic photosynthesis in the presence of hydrogen sulfide}, journal = {Genes}, volume = {12}, year = {2021}, month = {03/2021}, pages = {426}, abstract = {

Sulfide inhibits oxygenic photosynthesis by blocking electron transfer between H2O and the oxygen-evolving complex in the D1 protein of Photosystem II. The ability of cyanobacteria to counter this effect has implications for understanding the productivity of benthic microbial mats in sulfidic environments throughout Earth history. In Lake Fryxell, Antarctica, the benthic, filamentous cyanobacterium Phormidium pseudopriestleyi creates a 1\–2 mm thick layer of 50 \µmol L\−1 O2 in otherwise sulfidic water, demonstrating that it sustains oxygenic photosynthesis in the presence of sulfide. A metagenome-assembled genome of P. pseudopriestleyi indicates a genetic capacity for oxygenic photosynthesis, including multiple copies of psbA (encoding the D1 protein of Photosystem II), and anoxygenic photosynthesis with a copy of sqr (encoding the sulfide quinone reductase protein that oxidizes sulfide). The genomic content of P. pseudopriestleyi is consistent with sulfide tolerance mechanisms including increasing psbA expression or directly oxidizing sulfide with sulfide quinone reductase. However, the ability of the organism to reduce Photosystem I via sulfide quinone reductase while Photosystem II is sulfide-inhibited, thereby performing anoxygenic photosynthesis in the presence of sulfide, has yet to be demonstrated.\ 

}, keywords = {LTER-MCM}, doi = {10.3390/genes12030426}, url = {https://www.mdpi.com/2073-4425/12/3/426}, author = {Lumian, Jessica E. and Jungblut, Anne D. and Dillon, Megan L. and Hawes, Ian and Peter T. Doran and Mackey, Tyler J. and Dick, Gregory J. and Grettenberger, Christen L. and Sumner, Dawn Y.} } @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.} }