Aqueous geochemical and microbial variation across discrete depth
intervals in a peridotite aquifer assessed using a packer system in the
Samail Ophiolite, Oman
Abstract
The potential for molecular hydrogen (H-OH-
groundwaters bearing up to 4.05 μmol⋅L-1
H2 , 3.81 μmol⋅L-1 methane
(CH4) and 946 μmol⋅L-1 sulfate
(SO42-) revealed an ecosystem
dominated by Bacteria affiliated with the class Thermodesulfovibrionia,
a group of chemolithoheterotrophs supported by H2
oxidation coupled to SO42- reduction.
In shallower, oxidized
Mg2+-HCO3-
groundwaters, aerobic and denitrifying heterotrophs were relatively more
abundant. High δ13C and δD of CH4 (up
to 23.9 ‰ VPDB and 45 ‰ VSMOW , respectively), indicated microbial
CH4 oxidation, particularly in
Ca2+-OH- waters with evidence of
mixing with
Mg2+-HCO3- waters.
This study demonstrates the power of spatially resolving groundwaters to
probe their distinct geochemical conditions and chemosynthetic
communities. Such information will help improve predictions of where
microbial activity in fractured rock ecosystems might occur, including
beyond Earth.