This project will determine the origin of microcrystalline carbonate in stromatolites: is it precipitation resulting from bacterial metabolic activity, or physical trapping of resuspended particles? Crusting and "soft" mats from Exuma Cays, Bahamas, will be compared, with experimental intervention to encourage or inhibit lithification. Analyses will include structure and mineralogy of grains, structure of microbe community, mat physiology, and biogeochemistry of stable isotopes and extracellular secretions.
