Emerging Views of Sediment- Buried Ocean Basement Biosphere James P. Cowen Department of...
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Emerging Views of Sediment-Emerging Views of Sediment-Buried Buried
Ocean Basement BiosphereOcean Basement Biosphere
James P. CowenJames P. CowenDepartment of Oceanography Department of Oceanography
University of HawaiiUniversity of [email protected]@soest.hawaii.edu
Emerging Views of the Biosphere w/in Aging Ocean Basement
• Ocean basement provinces
• Biosphere of aging basement
– Access—tough
– General physical (e.g., fluid flow; temperature) and chemical characteristics
– Evidence of extant biosphere
– Speculated metabolic pathways
– Challenges and future research directions
Why do we care?• Ocean basement is a huge volume
• Potential for extensive biomass– Basalt to gabbro rocks
• Prone to alteration disequilibria
– Fluids circulate even in old basement
– Thermal, chemical gradients
• Potential for exotic metabolisms/strategies
• Analogue for extraterrestrial fluid covered, rocky bodies
Zone I: Ridge axis— active exchange
— high/low temperature venting;
— sharp thermal / redox / chemical gradients
Zone II: Unsedimented ridge flank— active (advective) exchange, low (to high ?) temperature venting
— poorly explored
Zone III: Sedimented ridge flanks (a) and basin (b)—increasing sediment cover;
—hydrologic seal at ~165 m thickness
—conductive heat / diffusive chemical exchange
Diffuseupwelling Impenetrable
~165 m
Zone IV: Exposed rocky outcrops (Seamounts)— Local advective recharge or discharge;
— Natural access to fluids
Access to crustal fluids
ODP/IODP Boreholes - Sediment and basement cores
- Observatories: CORKs (Circulation Obviation retrofit Kits)
* Engineered access to basement rock and fluids
Heat (temp)Basement ageSpreading rateSedimentation
Fluid FlowPermeability
PorosityDriving energy
GeochemicalRedox potential
Essential elementsWater/rock
Rock mineralogy
BiologicalDiversityBiomass
MetabolismActivity/survival
Consortia
0.8 My 3.5 My
Basement temperatures(east flank JFR)
0 20 40 60 80 100 120
Distance from ridge axis (km)
from Davis et al. 1999
Schultz and Elderfield 1997
Ocean Lithospheric Heat FluxTotal: ~32 TWHydrothermal circulation to 65 Ma:
~11 TWOff-axis (1-65 Ma) heat flux:
~9.25 TW
Associated Water FluxNear ridge (0-1 Ma): ~3.7 x 1016 g/yr
Flanks (1-65 Ma): ~0.2-2 x 1019 g/yr
Flank fluid flow = 50-500 X Axial flow
Cycle entire ocean through flank basement in70,000 to 700,000 yrs
Mottl 2004
Low Temp
Bulk Permeability of Upper Basement Crustal Age
Fisher (2004)Fisher (2004)
Suggests a decrease In bulk flow w/in aging basement
Consistent with seismic velocity (faster in denser, less porous media),
but inconsistent with heat flow obs(signif. advective heat loss to 65 My)
Borehole 395A: MAR flanks
modified from Matthews et al. (1984), modified from Matthews et al. (1984), Becker et al. (1998)Becker et al. (1998)
• • Zones of deflection in Zones of deflection in SP log (10-100 m thick)SP log (10-100 m thick)
Suggest:Suggest:Channelized flowChannelized flow
measures pressure differences
Basement rock/fluid chemistry
– Temperature of rocks (e.g., <2 to >100oC)
– How much fluid previously passed• History of fluids
– Composition of host rock (primary/secondary mineralogy)
• age
• water : rock ratios
• flow rates (i.e., general and local permeability)
• microbial activity
Marescotti et al 2000
Basement mineral alteration (bulk basement rock)
JdFR flanks
Age of basement
Distance from ridge axis
Fe2+
(Fe2++Fe3+)
Alt and Mata 2000
FeO
OH
Cel
adon
ite/
sapo
nite
Pyr
ite
Oliv
ines
Bach and Edwards 2003
Alteration Halo within Fracture (fluid conduit)
Microbial role ?
FeO
OH
Cel
adon
ite/
sapo
nite
Pyr
ite
Oliv
ines
O2
Fe2+
H2
Furnes and Staudigal1999estimate 75% of upper basement is microbially altered !?
O2 reduction
NO3- reduction
Fe3+ reductionSO4
2- reduction
+ H2 oxidation
Fe+2 oxidationS oxidationO2,NO3
- +
Making a Living
Chemolithoautotrophy:
Energy: Oxidation/reduction reactions using inorganic e- donor & e- acceptor pairs
C-source: inorganic (CO2)
Photoautotroph
Chemotroph
(reduced) organic carbon
Chemoorganotroph (heterotroph)
Chemolithoautotroph organic carbon
in Subseafloor Basement Environments
In situ abiogenicorganic carbon
Relevant, microbially meaningful reactions (chemolithoautotrophic)
4FeO + O2 + 6H2O = 4Fe(OH)3,s
[5FeO + NO3- + H+ + 7H20 = 5Fe(OH)3,s + 0.5N2]
FeS + 2O2 = Fe2+ + SO42-
2 FeO + 4 H2O = 2 Fe(OH)3 + H2
2 FeO + 2 H2O = 2 FeOOH + H2
2 FeO + H2O = Fe2O3 + H2
H2 oxid by O2, NO3-, Fe3+, SO4
2-,
Low-To, abiogenic anaerobic hydrolysis
Aerobic Fe2+ oxidation
Anaerobic Fe2+ oxidation
Sulfide oxidation
H2 oxidation
Potential metabolic processes active in subseafloor basement
e- donor e- acceptor By-product Subsurface habitat zonesa
H2 NO3-, NO2
-, N20, NO, N2 NH3, N2, NO2-, NO, N2O I, II, IVa,b
H2 SO42-, SO3
2-, S2O32-, S4O6
2-, S H2S, S2O32 I, II, IIIa,b, IVb
H2 CO2 Acetic acid I, II, IIIa,b, IVb
NH3 NO2-, MnIV N2, MnII I, II, IIIa, IVa
S2- NO3- NH3, SO4
2- I, II, IIIa, IVa
S2- NO3- NH3, S
0 I, II, IIIa, IVa
Organic-C SO42-, SO3
2-, S2O32-, S CO2, CH4, CO, reduced S I, II, IIIa,b, IVb
Organic-C O2 CO2 I, II, IVa
Organic-C NO3- NO2
-, N2, NH3, CO2 I, II, IV
H2, CH4, NH3,
S-2, FeII, MnII
O2 H2O, CO2, NO2-, NO3
-, FeIII,
MnIV
I, II, IIIa, IVa
Organic-C Organic-C (fermentation) I, II, III, IV
Organic-C, FeIII, other minerals I, II, IIIa,b, IVbGr = Gr
0 + RT ln(Q) Q = activity product?
Bottom seawater
BasementFluids
(1.2 Ma; 40.5oC)
BasementFluids
(3.5 Ma; 64oC)
pH 7.9 7.2 7.4
Alkalinity (meq/l) 2.5 1.4 0.6
SO42- (mmol/kg) 26.1 26.5 17.5
Mg2+ (mmol/kg) 52.5 27.5 4
Ca2+ (mmol/kg) 10.3 34.2 56.2
TCO2 (mmol/kg) 2.4 1.4 0.5
CH4 (mol/kg) <0.002 0.4 1.8
H2 (mol/kg) ~0.0002 0.4 0.6
NH3 (mol/kg) 0.9 60 90
Mn (mmol/kg) 0.0 48 4
Fe (mmol/kg) 0.0 62 1.1
Si (mmol/kg) 190 590 750
Cowen et al. 2003; Wheat et al. in review; M. Lilley, unpubl. data
Fluid Composition
Enriched Depleted
Basement fluid chemistryDepleted Mg2+/ enriched Si, Ca2+, Sr2+, H2
– Reaction with basaltic rocks
Enriched H2
– Hydrolysis of ferrous Fe in basalt rocksDepleted sulfate
– Sulfate reduction (H2, Org-C)– Diffusion to sediments– Sulfate mineral precipitation (e.g., Jarosite, anhydrite)
Elevated ammonia– Nitrate reduction (e.g., e- donor: Org-C, Fe2+, or H2)– N2 fixation – Diffusion from sediments
Depleted TCO2, alkalinity– Carbonate precipitation
Enriched Si, Fe– Seawater-basalt reactions– Contamination (e.g., drilling ops, borehole casings)
Furnes et al. 2001
MAR7 mbs<2 Ma
Reykj R51 mbs2.3 Ma
Reykj R124 mbs
38 Ma
Lau3 mbs4-7 Ma
MAR45 mbs10 Ma
MAR157 mbs10 Ma
Inferred Microbial-Produced Alteration Textures
mbs: meters below sediments
BSE-SEMimages
Torsvik et al. 1998
Phase contrast
DNA (DAPI)
Arch344
Bac388
Phase contrast
DNA (DAPI)
Bac388
Arch344
~50 mbs ~120 mbs
Costa Rica Rift
Fluorescent in situ hybridization—probes specific for Bacteria or Archaea
Torsvik et al. 1998
Costa Rica Rift~100 mbs5.9 Ma
Elemental X-ray maps
C
P
N
resin in fracture
(S)
(K)
Other maps:Si, Mg, Ca, Na depletedTi, Al, Fe, Mn, enriched
Costa Rica Rift~100 mbs5.9 Ma
Borehole 1026b basement fluids:
Phylogenetic tree (ssu rRNA):
bacterial groups
1026B clones’ closest known relations:
Sulfate reducersFermentative heterotrophsNitrate reducers (NH3 production)N2 fixers? (NH3 production)Thermophilic members
-P
rote
oba
cte
riaL
ow
G
+C
Cowen et al. 2003
Borehole 1026b fluids:
Phylogenetic tree (ssu rRNA): Archaea
1026B clones’ closest known relations to:
Sulfate reducers
Genes from Yellowstone hot springsThermophiles
Cowen et al. 2003
0.8 My 3.5 My
Basement fluid ages(east flank JFR)
0 20 40 60 80 100 120
Distance from ridge axis (km)
from Davis et al. 1999
Fluid 14C ages: 1ky 9.9ky
recharge
4.5ky
Wheat et al. 2002Fisher et al. 2003
Cowen 2004, as modified from Wheat et al. 2002
Older, reduced
(partially) Reset time clockand redox conditions
Speculated characteristics of buried ocean basement biosphere
• Low cell abundance
• Slow growing
• Highly heterogeneous distributions (& activities)– Localized populations consistent w/ channelized flow
– Punctuated by recharge zones
• Diverse chemoautolithotrophic and heterotrophic (& unusual) metabolisms
• Microbial consortia likely important and associated with biofilm formation
Summary• Ocean Basement environments are dynamic and
complex • Biosphere within aging basement is predicted:
– Favorable temperature ranges, – Active fluid flow (is it enough?)– Reactive basaltic rocks – Existing (preliminary) phylogentic data consistent w/ chemical
data
• Challenges– Accessibility– Contamination
– Life perhaps ubiquitous, but low biomass/activity?
Future borehole observatory opportunities
• Cores from drilling operations
• Short and long-term observations
– In situ (downhole) instrumentation
– Fluid collections
– In situ incubations
– Other experiments (e.g., push-pull)
(seafloor and downhole)
Contamination issues
Drilling operations• Drilling muds, bottom seawater, sediments
Observatory materials• Packing cement
• Borehole casing
• Sample delivery tubing
In situ Chemical Redox Analyzer
dissolved O2, H2S, MnII, FeII, S2O3
2-, S4O62-, Sx
2-, S0, aqueous species of FeIII and FeS
In situ VoltammetricElectrochemical measurements
Starring Brian Glazer!
Cabled IODP CORK Observatory(Ocean Observatory Initiative)
– Power:
• In situ filtrations
• Temperature controlled in situ incubations
– Two-way communication: directed sampling• Fine-scale coordination w/geophysical exp.
• Response to perturbation (e.g., seismic/magmatic events)
• Chemical/particle tracer transport studies
Colleagues
Co-InvestigatorsStephen Giovannoni (OSU)Michael Rappe (OSU,UH)Fabien Kenig (UI, Chicago)Craig Taylor (WHOI) Brian Glazer (IfA, UH)David Butterfield (PMEL-NOAA)Paul Johnson (UW)
Students Rachel Shackelford (UH)Phyllis Lam (UH)Michael Hutnak (UW/UCSC)
Other indispensable colleaguesAndy Fisher (UCSC)Michael Mottl (UH)Geoff Wheat (UA, MBARI)
Funding: NSF--Ocean Instrumentation, LExEn, MO, NASA-UHNAI