Paper No. 6
Presentation Time: 10:15 AM
INITIAL CHARACTERIZATION OF CARBON FLOWS THROUGH MICROBIAL COMMUNITIES IN BEOWULF SPRING, AN ACIDIC HOT SPRING IN YELLOWSTONE NATIONAL PARK
Beowulf Spring is an acidic, sulfidic hot spring in Yellowstone National Park. Several geochemical zones including sulfur followed by iron oxide deposition zones are visually apparent. Rates of deposition are highly suggestive of microbially mediated processes. Previous work has surveyed the microbial communities present in these systems. While the energetics of sulfide and iron oxidation are suitable to support microbial activity, the carbon source supporting microbial growth has not been determined. The temperatures in Beowulf (approaching 80°C) are above the photosynthetic upper temperature limit which, combined with a lack of observable photosynthetic activity in the main stream channel, precludes photosynthesis as a main carbon supplier for the system. Geochemical analyses suggest several possible sources of carbon in the area, including dissolved inorganic carbon, dissolved organic carbon, and methane. To determine the source(s) of carbon, we are employing geochemical and stable isotope techniques to assess carbon inventories and ultimately track carbon flows within Beowulf.
Initial stable isotope measurements focused on bulk isotope analysis of microorganisms in distinct geochemical zones within the spring, as well as carbon sources within and around the spring. Our data show that the carbon sources have distinct stable isotope ratios. Isotopic similarity between dissolved organic carbon and organic soil carbon suggests a common carbon source – most likely local vegetation. Correlation between d13C of microbial biomass and dissolved organic carbon are suggestive of some heterotrophic component in the mats, but this does not completely explain our isotope observations. We are currently in the process of using compound specific isotope analysis to examine other potential carbon sources in the system, including CO2 and methane. Identifying potential geochemical and microbial carbon links will provide valuable information for future stable isotope probing experiments and will help further elucidate carbon cycling in this system.