Joye Lab University of Georgia

Biogeochemistry, Microbial Activity, and Microbial Distributions in Sediments of the Deep Slope

Joye LabUniversity of Georgia

S. Joye, M. Bowles, V. Samarkin, K. Hunter, K. Bowles, and K. Segarra,

andH. Niemann (University of Basel, Switzerland)

The Geobiological Engine

Gas Hydrate

Brine Pool

δ13CH4 = -45ä δ13CH4 = -60 to -65 ä

Beggiatoa sp.mat

Thiomargarita sp.mat

musselbed

Tube wormpatch

Sediment

Water Column

CH4

HCO3-

HS-

SO42-

Org CH2

Oil. alkanes

NO3-

AN

ME

AR

CH

SRB

VSB

Adv

ectiv

e/D

iffus

ive

Flux

CH4brine

CH4

CH4, oil,alkanes,

DOM

SRDOM AOM,HydOx

SO42- H2S

Sulfate reduction DOM, Hydrocarbon, VFA oxidation

CO2

CH3COOH

+H2

Methanogenesis (CO2, acetate); Homoacetogenesis

CH4

CO2

CH4

or VFA acetate

oil,

gas,

brin

e

Brine, alkanes, DOC, oil

Microorganisms-Macrofauna: positive and negative interactions possible

Macrofauna Response

Toxic? Optimal? Energy limited?

Joye et al. 2004

Biogeochemistry•biogeochemistry

- salts, dissolved gases, nutrients, organic matter• microbial activity

- sulfate reduction, methane oxidation, methaneproduction

2006: 29 cores processed from 9 different sites- greater depth resolution, little replication

between sites and/or habitats

2007: 71 cores processed from 9 different sites- goal was to evaluate within/between habitat/sitevariability (more cores but decreased depthresolution)

GeochemistryCores sectioned and pore water extracted with a

mechanical "squeezer"; pore water split and preserved for analyses.

push core

Microbial ActivityMeasuring microbial activity with radiotracers:

14Ccarbon

35Ssulfur

CH4 + SO42- CO3

2- + H2S + H2Omethane sulfate bicarbonate hydrogen sulfide water

push core

The microbial turnover of radioactive methane and sulfate is a way to measure anaerobic oxidation of methane (AOM) and sulfate reduction (SR) rates

Microbiology

Molecular Biology (ongoing)• DNA extraction and clone libraries• quantify abundance of specific groups by FISH

Organic Geochemistry (ongoing, HelgeNiemann)

• biomarkers

Classic Microbiology (ongoing)• cell counts

Amplify 16S rDNAgenes from

environmental samples

Develop markers for specific groups

of organisms

Hybridize ribosomes in intact cells with

fluorescent markers(FISH)

Identification by molecular phylogeny

Identification by lipid biomarkers

Methods to target ‘live’ biomassWho is there and What are they doing ?

cell wall

DNA

ribosomesWhat do I eat?

δ13C composition of cell material

Cartoon by B. Orcutt

Habitat Differences: Control

Control Core (no seepage), GC852

• low CH4 and DIC

• evidence for SO42- consumption and H2S production but

available SR rates are extremely low

• DOC and CH4 increase with depth so could fuel deeper SR

Habitat Differences: Brine

Brine Flow Core, AT340

• extremely high CH4 but not DIC (carbonate precipitation?)

• rapid SO42- depletion (SR plus upward brine advection)

• DOC and NH4+ concentrations elevated within brine

• AOM rates are ~50% of SR rates; a reductant other than CH4 is used by SRB

Habitat Differences: Oily Brine

Oily Brine Flow Core, MC853

• extremely high CH4 but, again, low DIC (carbonate ptt?)

• rapid SO42- depletion, limited H2S accumulation (faster advection?)

• DOC and NH4+ concentrations highest measured

• AOM rates are ~50% of SR rates; additional reductant

Habitat Differences: Beggiatoa mat

Beggiatoa mat core, AT340

• low CH4 and DIC; subsurface pH minimum due to H2S oxidation

• little SO42- depletion (rapid re-oxidation)

• low NH4+ but DOC increases substantially with depth

• AOM rates below detection; SR rates high (variable)

Habitat Differences: Pogonophora

Pogonophoran core, WR269/270

• high CH4 and DIC; elevated pH w/ depth

• rapid SO42- depletion and H2S accumulation

• low NH4+ but very high DOC (exudate from pogos?)

• unusual patterns of AOM and SR (decoupled)

Habitat Differences: Urchin

Urchin core, AC818

• high CH4 and DIC (highest observed)

• rapid SO42- depletion and H2S accumulation

• low NH4+ but high DOC (related to urchins/urchin activity?)

• AOM and SR on same scale; AOM > SR

Habitat Differences: AC601 Brine Pool

lake bottominside

edgeouteredge

~3m~40m

control

brine

0 500 1000 1500 2000-5

0

5

10

15

20

25

Cl- concentration (mM)

depth(cm)

controllake bottominner edgeedgeouter edge

0 5 10 15 20 25 30-5

0

5

10

15

20

25

SO4

2- concentration (mM)

depth(cm)


0 500 1000 1500 2000 2500 3000 3500-5

0

5

10

15

20

25

CH4 concentration (µM)

depth(cm)


Habitat Differences: AC601 Brine Pool0 500 1000 1500 2000

-5

0

5

10

15

20

25

Sulfate Reduction Rate (nmol cm-3

d-1

)

depth(cm)


SR Rate (nmol cm-3 d-1)

0 20 40 60 80 100-5

0

5

10

15

20

25

depth(cm)


0 5 10 15-5

0

5

10

15

20

25

AOM Rate (nmol cm-3

d-1

)

depth(cm)


Integrated Rates SR AOM % coupled Bi-MOG(mmol m-2 d-1) control 0.09 0.004 4 n.d.

outer edge 0.89 0.36 40 n.d.edge 35.4 0.28 0.8 0.02inner edge 18 0.04 0.2 0.06lake bottom 1.3 0.03 2 0.01

0 0.2 0.4 0.6 0.8 1 1.2-5

0

5

10

15

20

25

Bi-MOG Rate (nmol cm-3

d-1

)

depth(cm)


Bi_MOG Rate (nmol cm-3 d-1)AOM Rate (nmol cm-3 d-1)

DOC vs. Cl-

0

2000

4000

6000

8000

500 1000 1500 2000 2500

340 br DOC 340 mt DOCAC818 ur DOC

GC852 ct DOC

MC853 obr DOCMC853 br2 DOC

AC818 tw DOCAC601 bot DOC

AC601 ur DOC

DO

C (µ

M)

Chloride (mM)

µM D

OC

Brines are enriched with DOC

Animal cores show increases with DOC over depth independent of salt;TW most extreme

Controls also show some increase with depth

NH4+ vs. Cl-

340 br DOC 340 mt DOCAC818 ur DOC

GC852 ct DOC

MC853 obr DOCMC853 br2 DOC

AC818 tw DOCAC601 bot DOC

AC601 ur DOC

0

2000

4000

6000

8000

0 500 1000 1500 2000 2500

DO

C (µ

M)

Chloride (mM)

µM N

H4+

Brines are enriched with NH4

+; differences b/tbrines (MC > AT = AC)

Animal cores little enrichment with depth (except for AT340 mat)

Habitat Differences: Within Site

AT340-CH4

• highest CH4 in mat and brine environments

• increases with depth at all sites (less control)

• means with different letters are significantly different at α = 0.05 level

0 500 1000 1500 2000 2500

-1

1.5

4.5

8

12.5

AT340 Cross habitat - Methane

controlurchinmatbrine

CH4 (µmoles/L)

Depth(cm)

a

bb

a

cb

a

cb

ab

b

a

bb


AT340-DIC• highest DIC in brines



0 5 10 15 20

-1

1.5

4.5

8

12.5

DIC ( mmoles/L)

Depth(cm)


a

b,c

ab

b,c

a, ba, b

c

ab

bb

abbb

ab

bb


AT340-NH4+

• highest NH4+ in brines

(mat, brine)



0 200 400 600 800 1000

-1

1.5

4.5

8

12.5

NH4+ (µmoles/L)

Depth(cm)


a

b

a

c

b

d

ab

cc

a

c

a

cd

d

b

b

b

Habitat Differences Across Sites-Pogos

Pogonophoran-SR rates• maximal SR rates at

WR269/270

• rates in pogo cores from WR269 and AC818 comparable; AC645 lower


0 10 20 30 40 50

-1

1.5

4.5

8

12.5

WR SRR645 SRR818 SRR

SR rate (nmol/cc/day)

Depth(cm)

a

aa

a

bb

a

a,bb

a

ab

Summary

1. Substantial habitat-associated variability in geochemistry and microbial activity: SR rates highest at brine sites; brines > microbial mats > pogos ~ tubeworms > urchins

2. Variability also noted in AOM rates: AOM rates highest at pogo sites (pogos > urchins > tubeworms > mats >>> brines)

3. Brine flow limits microbial activity: advection limits SO42-

availability and thus SR rates; AOM also hindered (salt?)

4. AC601 brine pool: highest SR activity at pool edges--best of both worlds (SW-SO4

2- and brine DOC?); AOM hindered and equal to MOG in the brine

Summary

5. Brines are a source of DOC and NH4+: Can see differences

in source fluids evident in slopes of chloride vs. DOC/NH4 plots.

6. Animals also a source of DOC?: Appears so. Labile organic C profiles will shed light on this (ongoing)

7. Significant differences between habitats within a site?: Yes! Replication between n=4 cores per habitat surprisingly good. Interactions between animals and microbial activity is clear; driving factors less clear

Remaining Work

Molecular biology: detailed studies of habitat variation (AT340 and AC601) and between site (pogos @ WR269, AC645 and AC818)

Remaining Geochemistry: labile DOC components (VFA); cations

Contributions to DSR Special IssueJoye, S.B., M.W. Bowles, V.A. Samarkin, K.S. Hunter, and H.

Niemann. Submitted. Biogeochemical signatures and microbial activity of different cold seep habitats along the Gulf of Mexico lower slope. Submitted to Deep Sea Research.

Orcutt, B.N., S.B. Joye, S. Kleindienst, K. Knittel, A. Ramette, A. Reitz, V.A. Samarkin, T. Truede, and A. Boetius. Submitted. Impact of natural oil and higher hydrocarbons on microbial diversity, distribution and activity in Gulf of Mexico cold seepsediments. Submitted to Deep Sea Research.

Wankel, S.D., S.B. Joye, V.A. Samarkin, S. Shah, G. Friderich, J. Melas-Kryiazi, and P.R. Girguis. Submitted. New constraints on diffusive methane fluxes and rates of anaerobic methane oxidation in a Gulf of Mexico brine pool through the use of a deep sea in situ mass spectrometer. Submitted to Deep Sea Research.

Planned PublicationsBowles et al. Methanogenesis at brine sites

Joye et al. AC601 brine lake (2006 cruise data)

Two to three additional biogeochemistry papers:

Joye et al. Habitat differences (2007 cruise data)

Joye et al. Brines comparison (2007 cruise data)

Joye, Roberts, et al. AC601 brine lake

Two to three molecular papers to be written by post doc Melitza Crespo-Medina: AT 340 paper, AC 601 paper and also a possible pogo paper

Reference

Joye, S.B., A. Boetius, B.N. Orcutt, J.P. Montoya, H.N. Schulz, M.J. Erickson, and S.K. Lugo. 2004. The anaerobic oxidation of methane and sulfate reduction in sediments from Gulf of Mexico cold seeps. Chemical Geology 205:219–238.

Joye Lab University of Georgia

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