Mechanisms of Calcium Carbonate Precipitation and Dissolution: Microbial Populations, Metabolic Processes and Mineral Products

University Of Connecticut, Storrs CT

Investigators

Abstract

Visscher Abstract This project is investigating the underlying mechanisms of carbonate precipitation in biologically active sediments by performing a geobiological study on a gradient from lithifying to non-lithifying microbial communities from microbial mats in a hypersaline pond (Eleuthera, Bahamas). Field measurements and in situ manipulations are being combined with a variety of laboratory experiments to isolate and characterize the biological processes and environmental variables that control carbonate precipitation. The PIs are examining microbial community composition, metabolic rates, and EPS characteristics in relation to carbonate mineral formation. Environmental parameters which are being investigated include water chemistry (e.g., pH, [Ca2+], [CO32-]) and light intensity. Microbial metabolism (production/consumption of inorganic carbon) on carbonate precipitation are being investigated by experimenting with pure and mixed bacterial cultures in both batch and continuous culture. By focusing on precipitation and dissolution along a natural gradient from lithifying mats to gelatinous EPS-rich mats, the PIs hope to understand the general rules that govern calcium carbonate precipitation by microbial communities. This information is being used to develop a mechanistic theory describing mineral precipitation in biologically active sediments. Since the main microbial guilds (cyanobacteria, sulfur oxidizers, sulfate reducers) responsible for carbonate precipitation are found in numerous environments, the theory developed will address the entire carbonate factory, the role of microbes in the formation of geologically important mineral products and the lithification and preservation of biological materials.