Abstract
To expand investigations into the phylogenetic diversity of microorganisms inhabiting the subseafloor biosphere, basalt-hosted crustal fluids were sampled from Circulation Obviation Retrofit Kits (CORKs) affixed to Holes 1025C and 1026B along the Juan de Fuca Ridge (JdFR) flank using a clean fluid pumping system. These boreholes penetrate the crustal aquifer of young ocean crust (1.24 and 3.51 million years old, respectively), but differ with respect to borehole depth and temperature at the sediment-basement interface (147 m and 39°C vs. 295 m and 64°C, respectively). Cloning and sequencing of PCR-amplified small subunit ribosomal RNA genes revealed that fluids retrieved from Hole 1025C were dominated by relatives of the genus Desulfobulbus of the Deltaproteobacteria (56% of clones) and Candidatus Desulforudis of the Firmicutes (17%). Fluids sampled from Hole 1026B also contained plausible deep subseafloor inhabitants amongst the most abundant clone lineages; however, both geochemical analysis and microbial community structure reveal the borehole to be compromised by bottom seawater intrusion. Regardless, this study provides independent support for previous observations seeking to identify phylogenetic groups of microorganisms common to the deep ocean crustal biosphere, and extends previous observations by identifying additional lineages that may be prevalent in this unique environment.
Highlights
While the Circulation Obviation Retrofit Kits (CORKs) affixed to Holes 1026B and 1025C were not designed with the intent to be exemplar platforms through which to investigate the microbiology of deep subsurface crustal fluids, they offer independent points of access that can serve to complement and verify observations made from other CORK platforms that were designed to maintain the biological integrity of retrieved borehole fluids, such as U1362A and U1362B on the Juan de Fuca Ridge (JdFR) flank (Fisher et al, 2012)
As priority for geochemical and microbiological sampling of older boreholes diminishes due to the antiquation of early-generation CORK materials and suboptimal fluid delivery systems, the likelihood of prioritizing research and submersible dive objectives in an effort to obtain fluid samples from them continues to decrease
This study add to previous research (e.g., Cowen et al, 2003; Nigro et al, 2012) that demonstrates that early generation CORKs are capable of yielding useful crustal fluid samples for comparative analysis, when significant flushing measures are employed
Summary
Several studies support the notion that the enormous volume of sediments and basement basalt that compose the global system of mid-ocean ridge spreading centers, flank and ocean basins harbors microbial life (e.g., Gold, 1992; Parkes et al, 1994; Fisk et al, 1998; Bach and Edwards, 2003; Cowen, 2004; D’Hondt et al, 2004; Schrenk et al, 2010; Orcutt et al, 2011a; Jungbluth et al, 2013). Fluids within the basement rock can be channeled up through the sediment horizon via fluid delivery lines and collected from sampling ports at the seafloor via submersible (Cowen et al, 2003; Huber et al, 2006; Cowen et al, 2012; Edwards et al, 2012; Lin et al, 2012; Nigro et al, 2012; Jungbluth et al, 2013)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
