Record Details
Geomicrobiology of marine sediment containing methane
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Geomicrobiology of marine sediment containing methane |
| Names |
Briggs, Brandon R.
(creator) Colwell, Frederick (advisor) |
| Date Issued | 2011-10-20 (iso8601) |
| Note | Graduation date: 2012 |
| Abstract | Marine sediments contain an abundance of methane that is biologically produced and plays a significant role in the global carbon cycle. Microbes responsible for the carbon cycle in marine sediments, and the processes that they carry out, need to be characterized in order to fully understand the role of this large methane reservoir in the global carbon cycle. The objective of this research was to describe the identity, distribution, and the factors that control distributions of microbes in three biogeochemical zones that are defined by methane in marine sediments, namely: the sulfate-methane transition (SMT), the gas hydrate occurrence zone (GHOZ), and the free gas zone (FGZ). Sediments from the Cascadia margins, Indian Ocean, Andaman Sea, and Ulleung Basin were examined. Fracture-dominated SMT environments from the Pacific and Indian Oceans harbored unique macroscopic biofilms composed of ANME-1 and Deltaproteobacteria. These biofilms contained 1-2 orders of magnitude more cells cm⁻³ than the surrounding sediment. The Andaman Sea sediments occur in a unique forearc basin that contains biogenic methane; yet, the organic carbon content here is lower than similar environments. Sediments from the Andaman Sea contained 1-2 orders of magnitude fewer cells cm-3 than typical hydrate-containing sediments and members of the Firmicutes such as Bacillus species dominated the microbial community. Statistical analysis of the molecular data using non-metric multidimensional scaling (NMS) and multi-response permutation procedures indicated that the GHOZ in the Andaman Sea contains a microbial community distinct from communities above and below the GHOZ. The measured abiotic variables most closely associated with the community structure were the concentration of organic carbon and variables associated with increasing depth. The Ulleung Basin sediments from above and below the SMT contained Deltaproteobacteria and the marine benthic group-B. NMS and cluster analysis identified two distinct microbial communities in the GHOZ of the Ulleung Basin. The microbial communities in the GHOZ that were typically closer to layers that contained higher hydrate saturation had indicator taxa related to Vibrio-type species. NMS ordinations also indicated that microbial communities from all three zones (SMT, GHOZ, or FGZ) were distinct from each another. Future refinements of total subsurface cellular abundance will benefit by including the cell abundance terms reported here. In addition, the biogeography of methane-containing sediments presented here will aid in understanding the carbon cycle in marine sediments by identifying environmental constraints on microbial taxa. |
| Genre | Thesis/Dissertation |
| Topic | Anaerobic oxidation of methane |
| Identifier | http://hdl.handle.net/1957/25778 |
