Metabolic activity and biosignatures of microbes in the lower ocean crust of Atlantis Bank, IODP Expedition 360

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Author(s): Wee, Shu Ying; Edgcomb, V. P.; Burgaud, G.; Klein, F.; Schubotz, F.; Yvon-Lewis, S. A.; Sylvan, J. B.
Author Affiliation(s): Primary:
Texas A&M University College Station, Oceanography, College Station, TX, United States
Other:
Woods Hole Oceanographic Institution, Geology and Geophysics Department, Woods Hole, MA, United States
MARUM - University of Bremen, Bremen, Germany
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: International Ocean Discovery Program (IODP) Expedition 360 represents the first leg of a multi-phase drilling program, SloMo, aimed at investigating the nature of the lower crust and Moho at slow spreading ridges. The goal of Expedition 360 was to recover a representative transect of the lower oceanic crust formed at Atlantis Bank, an oceanic core complex on the SW Indian Ridge. Recovered cores were primarily gabbro and olivine gabbro, which may potentially host serpentinization reactions and associated microbial life. Our goal was to sample this subseafloor environment and determine quantity, diversity and metabolic capabilities of any resident microbial life. Hole U1473A was drilled during Expedition 360 down to ≈790 m below seafloor and samples for detection of microbial communities and microbial biosignatures were collected throughout. We present here quantification of microbial biomass via fluorescence microscopy, preliminary analysis of nutrient addition experiments, data from sequencing of microbial 16S rRNA genes, analysis of microbial lipids, and data from Raman spectra of subsurface isolates. We initiated and sampled 12 nutrient addition experiments from 71-745 mbsf by adding sampled rocks to artificial seawater with no additions, added ammonium, added ammonium plus phosphate, and added organic acids. In nearly all of the experiment bottles, methane was detected when samples were collected at six months and again after one year of incubation. Phosphate in the incubations was drawn down, indicating active microbial metabolism, and archaeal lipids from in situ samples indicate the presence of methanogens, corroborating the likelihood of methanogens as the source of detected methane in the nutrient addition incubations. Altogether, the interdisciplinary approach used here provides a peek into life in the subseafloor upper ocean crust.
Year of Publication: 2017
Research Program: IODP2 International Ocean Discovery Program
Key Words: 22 Environmental Geology; Atlantis Bank; Crust; Ecology; Expedition 360; Indian Ocean; International Ocean Discovery Program; Metabolism; Oceanic crust; SloMo; Southwest Indian Ridge
Coordinates: S324225 S324220 E0571645 E0571635
Record ID: 2019008532
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