Benthic mat observations
The morphology of shallow water microbial mats at Lake Fryxell is influenced by the nucleation of gas bubbles on the mats (Wharton et al. 1982, Wharton et al. 1994). Gas bubbles build up in mats and induce buoyant delamination of mat layers, creating microbial mat liftoff structures. Liftoff mat was present to 6.4 m depth in 2006 (7.0 m depth in 2012; Figure 2A-B). Liftoff was not present below 7.0 meters in 2006 and was also absent from the deeper transect starting at ~8.5 m in 2012. Video footage throughout the 2012 oxycline shows ridge-pit and prostrate mat overlying discrete cm-scale, mineralized topographic highs or knobs (Figure 2C).