|Project Title||IODP Expedition 336 Objective Research: The deep biosphere of young and oxic oceanic crust|
|Acronym||North Pond basalts|
|Created||September 10, 2015|
|Modified||September 10, 2015|
Description from NSF award abstract:
The proposal addresses a fundamental aim of the ocean drilling program, namely to help characterize one of the largest and least studied ecosystems on Earth, the deep biosphere of the igneous crust buried below the ocean floor. The principal scientific objective of IODP expedition 336 is, in particular, to investigate the microbial population in basaltic crust from the North Pond area near the Mid-Atlantic Ridge. The study samples are weathered and porous basalts taken from beneath ~100 m of sediment in the North Pond area. The study proposes to determine both the diversity of the microbe population (using DNA) and its metabolic activity (using RNA). The PIs will investigate the relationship between microbes in the basement and those in the water column and determine which metabolic pathways are used by the deep basement microbes. The study will also provide baseline data for the long-term biological observatories installed in the sub-seafloor basement during expedition 336. Understanding deep biosphere life is a major thrust of the new IODP science plan and has implications for understanding the limits of life.
|Beth N. Orcutt||Bigelow Laboratory for Ocean Sciences||Principal Investigator|
|Katrina J. Edwards||University of Southern California (USC)||Co-Principal Investigator|
|Jason B. Sylvan||Texas A&M University (TAMU)||Co-Principal Investigator|
|Heath J. Mills||University of Houston (UH-Clearlake)||Co-Principal Investigator|
AbstractDuring the past decade, the IODP (International Ocean Discovery Program) has fostered a significant increase in deep biosphere investigations in the marine sedimentary and crustal environments, and scientists are well-poised to continue this momentum into the next phase of the IODP. The goals of this workshop were to evaluate recent findings in a global context, synthesize available biogeochemical data to foster thermodynamic and metabolic activity modeling and measurements, identify regional targets for future targeted sampling and dedicated expeditions, foster collaborations, and highlight the accomplishments of deep biosphere research within IODP. Twenty-four scientists from around the world participated in this one-day workshop sponsored by IODP-MI and held in Florence, Italy, immediately prior to the Goldschmidt 2013 conference. A major topic of discussion at the workshop was the continued need for standard biological sampling and measurements across IODP platforms. Workshop participants renew the call to IODP operators to implement recommended protocols.
AbstractThe vast marine deep biosphere consists of microbial habitats within sediment, pore waters, upper basaltic crust and the fluids that circulate throughout it. A wide range of temperature, pressure, pH, and electron donor and acceptor conditions exists—all of which can combine to affect carbon and nutrient cycling and result in gradients on spatial scales ranging from millimeters to kilometers. Diverse and mostly uncharacterized microorganisms live in these habitats, and potentially play a role in mediating global scale biogeochemical processes. Quantifying the rates at which microbial activity in the subsurface occurs is a challenging endeavor, yet developing an understanding of these rates is essential to determine the impact of subsurface life on Earth's global biogeochemical cycles, and for understanding how microorganisms in these “extreme” environments survive (or even thrive). Here, we synthesize recent advances and discoveries pertaining to microbial activity in the marine deep subsurface, and we highlight topics about which there is still little understanding and suggest potential paths forward to address them. This publication is the result of a workshop held in August 2012 by the NSF-funded Center for Dark Energy Biosphere Investigations (C-DEBI) “theme team” on microbial activity (www.darkenergybiosphere.org).
AbstractA remarkable number of microbial cells have been enumerated within subseafloor sediments, suggesting a biological impact on geochemical processes in the subseafloor habitat. However, the metabolically active fraction of these populations is largely uncharacterized. In this study, an RNA-based molecular approach was used to determine the diversity and community structure of metabolically active bacterial populations in the upper sedimentary formation of the Nankai Trough seismogenic zone. Samples used in this study were collected from the slope apron sediment overlying the accretionary prism at Site C0004 during the Integrated Ocean Drilling Program Expedition 316. The sediments represented microbial habitats above, within, and below the sulfate–methane transition zone (SMTZ), which was observed approximately 20 m below the seafloor (mbsf). Small subunit ribosomal RNA were extracted, quantified, amplified, and sequenced using high-throughput 454 pyrosequencing, indicating the occurrence of metabolically active bacterial populations to a depth of 57 mbsf. Transcript abundance and bacterial diversity decreased with increasing depth. The two communities below the SMTZ were similar at the phylum level, however only a 24% overlap was observed at the genus level. Active bacterial community composition was not confined to geochemically predicted redox stratification despite the deepest sample being more than 50 m below the oxic/anoxic interface. Genus-level classification suggested that the metabolically active subseafloor bacterial populations had similarities to previously cultured organisms. This allowed predictions of physiological potential, expanding understanding of the subseafloor microbial ecosystem. Unique community structures suggest very diverse active populations compared to previous DNA-based diversity estimates, providing more support for enhancing community characterizations using more advanced sequencing techniques.
AbstractThe objective of this study was to determine shifts in the microbial community structure and potential function based on standard Integrated Ocean Drilling Program (IODP) storage procedures for sediment cores. Standard long-term storage protocols maintain sediment temperature at 4°C for mineralogy, geochemical, and/or geotechnical analysis whereas standard microbiological sampling immediately preserves sediments at −80°C. Storage at 4°C does not take into account populations may remain active over geologic time scales at temperatures similar to storage conditions. Identification of active populations within the stored core would suggest geochemical and geophysical conditions within the core change over time. To test this potential, the metabolically active fraction of the total microbial community was characterized from IODP Expedition 325 Great Barrier Reef sediment cores prior to and following a 3-month storage period. Total RNA was extracted from complementary 2, 20, and 40 m below sea floor sediment samples, reverse transcribed to complementary DNA and then sequenced using 454 FLX sequencing technology, yielding over 14,800 sequences from the six samples. Interestingly, 97.3% of the sequences detected were associated with lineages that changed in detection frequency during the storage period including key biogeochemically relevant lineages associated with nitrogen, iron, and sulfur cycling. These lineages have the potential to permanently alter the physical and chemical characteristics of the sediment promoting misleading conclusions about the in situ biogeochemical environment. In addition, the detection of new lineages after storage increases the potential for a wider range of viable lineages within the subsurface that may be underestimated during standard community characterizations.
I was honored to receive a DEBI RCN Graduate Student Education Exchange grant for research at the IODP Kochi Institute for Core Sample Research in Kochi, Japan. During the month of July 2010, I worked with Dr. Fumio Inagaki and other members of his lab group to learn his techniques of cell enumeration and flow cytometry. The experience of working in his lab allowed me to go beyond the typical collaboration based on brief meetings and email exchanges alone. I was able to step outside of my comfort zone and have a research experience in an unfamiliar culture. I learned much more than research techniques including overcoming communication barriers, building collaborations, and cultural exchanges. I discovered that the basic standards of science are global and although communication was difficult with a few lab members, the language of science transcended that and we continued to learn from each other regardless. The methods I have learned in Japan have given me the ability to expand on my skill set and apply it to various environments. Since working with Dr. Inagaki, the techniques I have learned have allowed me to work on samples collected from research cruises in the Gulf of Mexico and IODP Leg 325 in the Great Barrier Reef. Dr. Inagaki encouraged me to ship and work on my own samples in order to return to my home institution with data that I am able to directly incorporate into my dissertation. We have since discussed other collaboration opportunities and I look forward to what the Research Coordination Network can provide in the future.