Microbial Communities in Sediments from the Bpxa-Doe Mt. Elbert Gas Hydrate Research Well
High latitude soils and sediments often contain large quantities of methane that may be partially consumed or produced by microbial communities. We studied the microbial communities collected from hydrate-bearing sediments on the North Slope of Alaska to determine how abiotic variables (e.g., grain size, hydrate presence, original depositional environment) may control the type and distribution of microbes in the sediments. The cores were acquired from sub-permafrost, Eocene (35-36 million years ago [MYA]) sediments within which hydrates are believed to have formed 1.5 MYA. Forty samples, eight of which originally contained hydrates, were acquired from depths of ca. 606-666 meters below land surface. Five drilling fluid samples acquired from the same depth range were included in the analysis as a control for contamination during the drilling and handling of cores. DNA was extracted from the samples (typically <1 ng DNA/g sediment was recovered) and then amplified using polymerase chain reaction with primers specific for bacterial and archaeal 16S rDNA. Only bacterial DNA amplicons were detected. Terminal-restriction fragment length polymorphism (t-RFLP) was used to measure bacterial diversity in the respective samples. Non-metric multidimensional scaling (NMDS) was used to determine the abiotic variables that may have influenced bacterial diversity. NMDS analysis revealed that sediment samples were distinct from those obtained from drilling fluids suggesting that the samples were not contaminated by the drilling fluids. Microbes were present in all samples and sample depth, temperature, and hydrate presence appeared to influence community diversity as evidenced by common t-RFLP profiles. Further examination of selected samples using clone libraries may help to identify the key taxa present in these unique sediments and yield a better understanding of the biogeochemistry of these gas-bearing systems.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009