LIPID BIOMARKERS AND ISOTOPE SIGNATURES ASSOCIATED WITH TRAVERTINE DEPOSITS IN A YELLOWSTONE HOT SPRING, USA

Microbial mats encrust travertine deposits in different lithofacies from vent to distal slope along the continuous drainage outflow system of a hot spring (Angel Terrace AT-1) in the Yellowstone National Park, USA. Mat materials were collected for lipid biomarker and carbon-isotope analyse in order to understand the carbon cycling dynamics in the mat communities. A vertical core was also taken in the pond facies to study the preservation of lipid biomarkers during travertine diagenesis. Phospholipid fatty acids (PLFA) in the mats exhibit distinctly different compositions in each of the facies, which is consistent with partitioning of bacterial 16S rRNA gene sequences, which has been observed in the Spring AT-1 travertine facies. Carbon isotope fractionations between lipid biomarkers and mat organic matter also differ from facies to facies, which suggest that different biosynthetic pathways are associated with distinct microbial communities in the changing environments. In the vertical profile, lipid biomarkers decrease with depth and reflect microbial communities different from those in the surface mats. The results demonstrate that lipid biomarkers and isotope signatures in combination with molecular DNA serve as a powerful tool for identifying functional metabolism within a stratified community in modern hot spring systems.