Microbially induced carbonate dissolution was evaluated from sulfidic wells in the Edwards Aquifer, Texas. Filamentous biomass covers rock surfaces, with Gammaproteobacteria and Epsilonproteobacteria dominating the attached community, but novel Alphaproteobacteria dominating the planktonic community. Despite fluids being saturated with respect to calcite, experimental calcite from in situ microcosms had significantly greater mass loss when colonized. Moreover, neoformed gypsum crystals were observed on colonized surfaces where fluids were undersaturated with respect to gypsum. The results are similar to findings from shallow cave and karst environments, and highlight the underappreciated role of microbes in the modification of carbonate aquifers and reservoirs.

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