| dc.description.abstract | Olivine in the presence of seawater will undergo a reaction known as serpentinization to form the mineral serpentine in addition to hydrogen, methane, and short chain hydrocarbons, which can be metabolized by microorganisms. Environments where serpentinization reactions occur are therefore hypothesized to support microbial life. The goal of the International Ocean Discovery Program (IODP) Expedition 360 (X360) was to recover a representative transect of the lower oceanic crust formed at Atlantis Bank, an oceanic core complex on the southwest Indian Ridge. Recovered cores were primarily gabbro and olivine gabbro, which may potentially host serpentinization reactions and associated microbial life. The goal of this thesis project was to quantify in situ microbial cells, analyze the microbial community structure of the in situ rock samples, and assess if nutrient supply influences the microbial community and methane production using a nutrient addition incubation approach. It was found that the microbial cell abundance is positively correlated to vein presence in rocks for certain depths. Microbial community diversity, assessed via 16S rRNA amplicon analysis, was extremely variable with depth.
Additionally, different nutrient treatments added to incubations from twelve depths did not have an observable effect on the microbial diversity or methane production. Knowledge gained here will be useful in connecting microbial ecology in deep subseafloor basement to other marine and subsurface habitats. Altogether, the interdisciplinary approach used here provides a peek into life in the subseafloor upper ocean crust. | en |
