Chapter 6
MICROBIAL PROCESSES FORMING MARINE STROMATOLITES
Microbe-Mineral Interactions with a Three-Billion-Year Rock Record

by
R.P. Reid, C. Dupraz, P.T. Visscher, and D.Y. Sumner

in Fossil and Recent Biofilms, a natural history of life on Earth, W. E. Krumbein, D. M. Paterson, and G. A. Zavarzin, editors. Kluwer Academic Publishers, p. 103-118.


Research in the burgeoning field of geomicrobiology reveals an “intimate juxtaposition and interdependence” of microbes and minerals that we are only beginning to appreciate (Skinner 1997, p. 1). Future studies of microbe mineral interactions are likely to lead to major advances in our understanding of such fundamental issues as the dynamics of sedimentation, the flow of energy and matter through the biosphere, and the evolution of life on Earth (Nealson 2000, Nealson and Stahl 1997, Hazen 2001)

An ideal model system in which to study microbe-mineral interactions and ecological principles governing these interactions is modern marine stromatolites. Modern marine stromatolites are living examples of one of earth’s oldest and most persistent widespread ecosystems. Layered deposits of calcium carbonate known as stromatolites first appeared in the geological record at least three and a half billion years ago (Grotzinger and Knoll 1999, Hofmann et al. 1999). Stromatolites are neither biotic fossils nor abiotic structures. Rather, they represent the complex interactions of microbes, minerals, and the environment (Walter 1994, Grotzinger and Knoll 1999). For almost 80% of Earth’s history, stromatoliteforming microbial communities played a major role in regulating sedimentation and global cycles of major elements via production and decomposition of organic matter, trapping and binding of sediment, and precipitation of calcium carbonate.

Modern stromatolites in Exuma Cays, Bahamas, offer a unique opportunity to investigate interactions between microbes and minerals in the highly successful stromatolite ecosystem. In this paper, we examine microbial processes forming Exuma stromatolites. We review what is currently known and identify unanswered questions and future research directions. Our goal is to demonstrate that a thorough understanding of microbe-mineral interactions in modern marine stromatolites will have broad implications in a wide variety of fields, including ecology, biogeochemistry, sedimentology, and paleobiology, and will improve our ability to interpret the fossil record of ancient ecosystems.



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Dawn Y. Sumner
Department of Geology
University of California
Davis, CA 95616
sumner@geology.ucdavis.edu