NSF Award Abstract - #0221743

AWSFL008-DS3

BE/CBC: Geobiology and the Emergence of Terraced Architecture during Carbonate
Mineralization

Abstract

ABSTRACT

Objectives and Methods: The goal of this proposal is to determine how the biodiversity and activity of specific living microbes and/or microbial communities are required to create the terraced architectures universally observed in high-temperature and low-temperature carbonate spring deposits. Results will provide a fundamental knowledge of microbe-water-mineral interactions during carbonate precipitation that are needed to more accurately reconstruct the history of microbial life on earth and other planets. This project advances the field of biocomplexity by combining geological studies, microbial rDNA and gene analyses and quantitative modeling to provide a detailed geobiological account of carbonate terrace formation. The integrated multidisciplinary research and educational aspects of this project meet a national need to train personnel for future geobiology and biocomplexity studies.

The project is headed by a unique interdisciplinary research team with specific expertise in geology, microbiology, and physics. Project milestones include:1) performing in situ crystallization experiments to determine the form and chemistry of travertine deposited when the microbes have been UV-irradiated, a sterilization technique that will leave the other fundamental physical and chemical conditions of the spring drainage outflow relatively unchanged; 2) documenting associations between calcite crystal growth form, distribution and chemistry with microbial form, diversity and metabolic activity; and 3)quantitative modeling of carbonate terrace formation using stochastic differential equations to describe the combined effects of geological and biological processes.

Mammoth Hot Springs is the most appropriate natural laboratory in the world for conducting the proposed research. Although CO2 degassing and decreasing temperatures strongly influence the spring water chemistry, significant biological controls on travertine crystal form and isotope chemistry have recently been quantitatively documented. Mammoth Hot Springs uniquely offers:1) precipitation rates as high as 5 mm/day that allow short-duration in situ crystallization experiments in a regime of coupled biological and physical influences;2) the full spectrum of high-to low-temperature carbonate precipitates at one site;3) long-term familiarity of the study site by the PI 's who have all required research permits in hand; and 4)the only easily accessible hot spring complex in the world protected in its natural state.

Intellectual Merit: The main question addressed is whether the presence of terraced carbonate architecture is prima facie evidence for the presence of microbial activity. Results from this study will permit the identification of microbiologically influenced crystallization in other modern and ancient high-temperature and low-temperature terraced carbonate spring deposits. The techniques employed in the quantitative modeling provide a first principles understanding of significant geological features from a physical and biological perspective. Of equal importance, the results from this study will establish a systematic and quantitative toolkit to identify microbial influence during carbonate deposition that can be used in a wide variety of other important terrestrial, marine, and burial environments on earth and other planets. Broader Impacts: This systems-level understanding of the interaction between biological and geological processes and resultant conceptual approaches will provide learning opportunities at all levels from postgraduate to K-12, as well as to the general public. The program to train personnel in biocomplexity studies will include undergraduates, graduate students, and postdocs, international student exchange with the University of Siena in Italy, web-based curriculum development for Geobiology courses, and the development of a formal Geobiology program at Illinois. This project enhances public awareness of the need for biocomplexity studies through museum displays, brochures, and interpretive trail signs for the Canyon and Mammoth Hot Springs Visitor Centers in Yellowstone National Park, which will be seen and used by over 3 million park visitors each year.