title: Formation and stability of oxygen-rich bubbles that shape photosynthetic mats.
abstract: Gas release in photic-zone microbialites can lead to preservable morphological biosignatures. Here, we investigate the formation and stability of oxygen-rich bubbles enmeshed by filamentous cyanobacteria. Sub-millimetric and millimetric bubbles can be stable for weeks and even months. During this time, lithifying organic-rich laminae surrounding the bubbles can preserve the shape of bubbles. Cm-scale unstable bubbles support the growth of centimetric tubular towers with distinctly laminated mineralized walls. In environments that enable high photosynthetic rates, only small stable bubbles will be enclosed by a dense microbial mesh, while in deep waters extensive microbial mesh will cover even larger photosynthetic bubbles, increasing their preservation potential. Stable photosynthetic bubbles may be preserved as sub-millimeter and millimeter-diameter features with nearly circular cross-sections in the crests of some Proterozoic conical stromatolites, while centrimetric tubes formed around unstable bubbles provide a model for the formation of tubular carbonate microbialites that are not markedly depleted in (13)C.
authors.affiliation: EAPS, Massachusetts Institute of Technology, Cambridge, MA, USA. tbosak@mit.edu
authors.forename: T
authors.initials: T
authors.lastname: Bosak
authors.forename: J W M
authors.initials: JW
authors.lastname: Bush
authors.forename: M R
authors.initials: MR
authors.lastname: Flynn
authors.forename: B
authors.initials: B
authors.lastname: Liang
authors.forename: S
authors.initials: S
authors.lastname: Ono
authors.forename: A P
authors.initials: AP
authors.lastname: Petroff
authors.forename: M S
authors.initials: MS
authors.lastname: Sim
mesh_terms: D000458:Cyanobacteria / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D010100:Oxygen / Q000032:analysis / Q000737:chemistry*; D010788:Photosynthesis / Q000502:physiology*
chemical_list: D010100:Oxygen