Aquatic Sciences Meeting, Albuquerque 2001

SS43 Biogeochemical Processes in Stromatolites: A 3 b.y.old ecosystem (Spatial and Temporal Connections)

Date: Monday, February 12, 2001, Time: 4:30:00 PM

Location: Cimarron

Rogers, D, R, University of Connecticut, Groton, USA, daniel.rogers@uconn.edu

Visscher, P, T, University of Connecticut, Groton, USA, pieter.visscher@uconn.edu

THE ROLE OF SULFATE-REDUCING BACTERIA IN LITHIFICATION OF MODERN MARINE STROMATOLITES

Laminations in modern marine stromatolites (Exuma Cay, Bahamas) are formed by microbial communities resembling microbial mat communities commonly found in other locations. As in microbial mats, sulfur cycling is an important is pathway for carbon degradation in stromatolites. Sulfate-reducing bacteria (SRB) have been found to metabolize more than half of the carbon produced within mat structures. Previously, using radiolabeled sulfate, sulfate-reduction was shown to coincide with the lithified layers of the stromatolite. Using three pure cultures, isolated from the surface layers (first cm) of Bahamian stromatolites, we demonstrated that sulfate-reducing bacteria are capable of initiating and enhancing precipitation of calcium carbonate in culture. This passive precipitation could be a result of changing alkalinity through the respiration of the anaerobic bacteria. Growing cultures of sulfate-reducing bacteria are able to precipitate calcium carbonate at a rate of 51umol/hr, ten times faster the chemical precipitation (5umol/hr). These biologically enhanced precipitation rates in modern stromatolites are significant, possibly leading to the formation of lithified layers.

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Aquatic Sciences Meeting, Albuquerque 2001

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