02426nas a2200241   4500008004100000022001400041245010000055210006900155260001200224490000800236520166500244653001501909653001701924653002901941653002401970653002201994653001902016100002202035700002202057700001502079700002102094856006902115       2025                        eng d  a2169-895300aMorphology and distribution of bubble-supported microbial mats from ice-covered Antarctic lakes0 aMorphology and distribution of bubblesupported microbial mats fr  c03/20250 v1303 a<p>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 &ldquo;liftoff mats.&rdquo; 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.</p>10aAntarctica10abiosediments10abubble-driven morphology10agas-supersaturation10aice-covered lakes10amicrobial mats1 aJuarez-Rivera, M.1 aMackey, Tyler, J.1 aHawes, Ian1 aSumner, Dawn, Y.  uhttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JG00851602314nas a2200265   4500008004100000245012500041210006900166260001200235490000700247520147000254653001501724653001101739653001701750653001801767653001101785653004001796100002201836700001501858700002301873700002201896700002401918700002101942700002101963856006401984       2020                        eng d00aEnergetic and environmental constraints on the community structure of benthic microbial mats in Lake Fryxell, Antarctica0 aEnergetic and environmental constraints on the community structu  c02/20200 v963 a<p>Ecological communities are regulated by the flow of energy through environments. Energy flow is typically limited by access to photosynthetically active radiation (PAR) and oxygen concentration (O<sub>2</sub>). The microbial mats growing on the bottom of Lake Fryxell, Antarctica, have well-defined environmental gradients in PAR and (O<sub>2</sub>). We analyzed the metagenomes of layers from these microbial mats to test the extent to which access to oxygen and light controls community structure. We found variation in the diversity and relative abundances of Archaea, Bacteria and Eukaryotes across three (O<sub>2</sub>) and PAR conditions: high (O<sub>2</sub>) and maximum PAR, variable (O<sub>2</sub>) with lower maximum PAR, and low (O<sub>2</sub>) and maximum PAR. We found distinct communities structured by the optimization of energy use on a millimeter-scale across these conditions. In mat layers where (O<sub>2</sub>) was saturated, PAR structured the community. In contrast, (O<sub>2</sub>) positively correlated with diversity and affected the distribution of dominant populations across the three habitats, suggesting that meter-scale diversity is structured by energy availability. Microbial communities changed across covarying gradients of PAR and (O<sub>2</sub>). The comprehensive metagenomic analysis suggests that the benthic microbial communities in Lake Fryxell are structured by energy flow across both meter- and millimeter-scales.</p>10aAntarctica10aenergy10aLake Fryxell10amicrobial mat10aOxygen10aPhotosynthetically Active Radiation1 aDillon, Megan, L.1 aHawes, Ian1 aJungblut, Anne, D.1 aMackey, Tyler, J.1 aEisen, Jonathan, A.1 aDoran, Peter, T.1 aSumner, Dawn, Y.  uhttps://academic.oup.com/femsec/article/96/2/fiz207/5697196