What can deep sea hydrothermal vent mineral alteration tell us about chemolithotrophic microbes?

Abstract:

Hydrothermal venting is heated and chemically altered seawater releasing through cracks in the seabed to mix with deep ocean seawater. During active venting, chemolithotrophic microbial biofilms catalyze inorganic oxidation-reduction reactions using dissolved sulfur and metal species from the fluids. Once venting stops, dissolved chemicals are no longer available for microbial metabolism. It seems reasonable that, as in other marine low-temperature environments, previously precipitated chimney minerals should then become the sole energy source for microbial biofilms. Currently, the ecological succession from microbial communities dependent on actively vented fluids for energy to those dependent on inactive sulfide mineral deposits is mostly unknown. We are beginning to address this knowledge gap by describing changes to the microbial habitat from actively venting sulfide chimneys to hydrothermally inactive chimney deposits using an array of light microscopy, electron microscopy, and spatially resolved synchrotron approaches. Synchrotron microprobe X-ray fluorescence mapping (XRF), X-ray diffraction (XRD), and X-ray absorption spectroscopies (XAS) are being used to map element distributions and phase identification for crystalline and poorly-crystalline minerals. With this information we can describe how minerals change in space and time during the transition from ‘hot’ to ‘cold’ vent microbial habitats.