This study will characterize fluid composition and microbial community structure, define chemical and biological processes at South Chamorro Seamount, and constrain background physical and hydrogeologic conditions. Collection and analysis of the suite of samples and data will provide the foundation to (1) address pathways for mantle alteration and microbial functioning (e.g., AOM, H - oxidation), (2) constrain rates of abiotic and biotic mineral alteration and alteration mechanisms, (3) describe microbial abundance, diversity, metabolic rate, and ecological roles in this naturally occurring highly alkaline (pH 12.5) and sulfide-rich solution, (4) conduct culture enrichment studies, and (5) begin to understand how the hydrologic and mud flow systems respond to tectonic forcing.
Broader Impacts The potential broader impacts of this project include incorporation of education in research, through the involvement of graduate students. There is also a significant potential benefit to the broader scientific community in this work, and there is an important growing international collaboration as well.
", allowed myself and my graduate student to participate on two Japanese (JAMSTEC) cruises in January and May of 2009. During this time, we were able to collect microbial samples from a borehole that had been previously sealed (aka CORK’ed) using the remotely operated vehicle Hyperdolphin. We collected pristine fluids originating from the subsurface in an effort to better understand what microbes were present in these fluids and to gain a glimpse into what types of metabolisms might be possible under conditions of extreme high pH (~12.5). We collected eight samples with an average of 6 liters of borehole fluids filtered per sample. These samples were the basis of our molecular microbial investigations. We placed less emphasis on ribosomal gene cloning, while focusing our efforts on addressing the majority of our community structure analysis using the techniques known as terminal-restriction fragment length polymorphism (T-RFLP) and quantitative-polymerase chain reaction (Q-PCR) analyses, which are still ongoing. Our primary conclusion at this time is that overall numbers of cells are quite low at ~10,000 cells per milliliter in these fluids and that any archaeal cells present (unlike in the sediments, which are dominated by Archaea) are well below our level of detection by either method. The majority of the microbial cells found in this habitat have been confirmed as a diverse array of bacterial phylotypes. These results will be the basis of our next manuscript, which is currently in preparation. During the course of this study, we have characterized the fluid composition and the microbial community structure, defined chemical and biological processes at South Chamorro Seamount, and constrained background physical and hydrogeologic conditions as we now know them. We have collected and analyzed a suite of microbial samples and these data have provided the foundation to address questions regarding microbial functioning. We have described the microbial abundance, diversity, biomass, and ecological roles in this naturally occurring highly alkaline (pH ~12.5) and sulfide-rich fluids, which has also helped us in understanding how the hydrologic and mud flow systems respond to tectonic forcing. An understanding of these processes is critical to elucidating the interplay among tectonic forcing, hydrology, and biogeochemical processes. Active serpentinite mud volcanism has persisted throughout most of Earth’s history; sedimentary serpentinite containing benthic marine fossils is found worldwide. It is very likely that microbial communities existed in these relic deposits. This study has focused on the mechanisms for the inorganic synthesis of hydrocarbons coupled with DNA-based studies of bacteria and archaea. Results have demonstrated global ramifications for the origin of life on Earth and on other planetary bodies. The international community has also benefitted from this research as it has provided a foundation for future scientific ocean drilling and subseafloor observatories. This joint US-Japanese venture has introduced five new investigators to CORK-related science, provided both undergraduate and graduate students a unique learning experience, and enlighten K-12 students to some of the geologic, chemical, and microbial extremes on Earth.
