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 Hawaiijcowen@soest.hawaii.edujcowen@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

Detrick 2004

old old

Karson et al. 2002

bas

emen

toc

ean

crus

t

Ocean crust

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

2600

m29

00 m

CORK-I Observatory

Heat (temp)Basement ageSpreading rateSedimentation

Fluid FlowPermeability

PorosityDriving energy

GeochemicalRedox potential

Essential elementsWater/rock

Rock mineralogy

BiologicalDiversityBiomass

MetabolismActivity/survival

Consortia

JdF Ridgeflank

Lau Basin

Costa Rica RiftSouth flank

Reykajanes

MAR west flank

Global Ocean Basement

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

0 10 20 30 40 50 60Crustal Age (Ma)

JFR, CRR

Wheat et al. 2003

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)

Channelized flow

Fluid flows:

Rapid channelized

Tortuous advective

Diffusive flux

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+)

Johnson and Semyan 1994, reploted by Bach and Edwards 2003

Marescotti et al. 2000

JdFR Increasing (upper) Basement Age

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?

Edwards 2004

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)

Sediment-Basement Exchange:Borehole 1027 (3.5 Mya)

Mather and Parkes 2000

Sedimentsbasement

Mather and Parkes 2000

Borehole 1027: sediment profiles

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

Cowen et al. 2003

‘BioColumn’ basement fluid sampler

Cell products from basement fluids(1026b, JFR)

0.5 um

Propidium iodine-stained

Giovannoni

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

CORK-II Observatory

Downhole sampling

Cowen and Taylor, in development

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

Propidium iodine-stained sediment-buried basement fluids(1026b, JFR)

Giovannoni