title: Deep sub-seafloor prokaryotes stimulated at interfaces over geological time.
abstract: The sub-seafloor biosphere is the largest prokaryotic habitat on Earth but also a habitat with the lowest metabolic rates. Modelled activity rates are very low, indicating that most prokaryotes may be inactive or have extraordinarily slow metabolism. Here we present results from two Pacific Ocean sites, margin and open ocean, both of which have deep, subsurface stimulation of prokaryotic processes associated with geochemical and/or sedimentary interfaces. At 90 m depth in the margin site, stimulation was such that prokaryote numbers were higher (about 13-fold) and activity rates higher than or similar to near-surface values. Analysis of high-molecular-mass DNA confirmed the presence of viable prokaryotes and showed changes in biodiversity with depth that were coupled to geochemistry, including a marked community change at the 90-m interface. At the open ocean site, increases in numbers of prokaryotes at depth were more restricted but also corresponded to increased activity; however, this time they were associated with repeating layers of diatom-rich sediments (about 9 Myr old). These results show that deep sedimentary prokaryotes can have high activity, have changing diversity associated with interfaces and are active over geological timescales.
authors: School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3YE, UK. j.parkes@earth.cf.ac.uk
authors: R John
authors: RJ
authors: Parkes
authors: Gordon
authors: G
authors: Webster
authors: Barry A
authors: BA
authors: Cragg
authors: Andrew J
authors: AJ
authors: Weightman
authors: Carole J
authors: CJ
authors: Newberry
authors: Timothy G
authors: TG
authors: Ferdelman
authors: Jens
authors: J
authors: Kallmeyer
authors: Bo B
authors: BB
authors: Jørgensen
authors: Ivano W
authors: IW
authors: Aiello
authors: John C
authors: JC
authors: Fry
mesh_terms: D001105:Archaea / Q000235:genetics / Q000302:isolation & purification; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification; D044822:Biodiversity; D015169:Colony Count, Microbial; D004247:DNA / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D017377:Diatoms / Q000302:isolation & purification; D019015:Geologic Sediments / Q000382:microbiology*; D008697:Methane / Q000032:analysis; D008970:Molecular Weight; D010140:Pacific Ocean; D010568:Peru; D011387:Prokaryotic Cells / Q000145:classification / Q000166:cytology / Q000378:metabolism*; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013431:Sulfates / Q000032:analysis; D013997:Time Factors
chemical_list: D013431:Sulfates; D004247:DNA; D008697:Methane