Microbial Primary Productivity in Hydrothermal Vent Chimneys At Middle Valley, Juan de Fuca Ridge
B43G-0496
Heather C. Olins ([email protected], www.heatherolins.com), Daniel Rogers, Kiana L. Frank, Charles Vidoudez, Peter R. Girguis
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States
A) Little is known about rates of primary productivity at deep sea vents.
B) We sampled actively venting
hydrothermal chimney walls.
Chemolithoautotrophy is the fundamental process responsible for
immense prokaryotic and eukaryotic biomass around hydrothermal vents.
However, rates of primary productivity in these systems have received
relatively limited attention. Better constraining the rates of primary
productivity will allow a better understanding of carbon cycling in the
deep sea.
Here, we present microbial carbon fixation rates within hydrothermal
vent walls measured directly via 14C bicarbonate radiotracer experiments.
We consider these rates in the context of abiotic and biotic factors and
offer initial insights into the specific contribution that epi- and
endolithic microbes make to vent system primary productivity to
identify the role that these systems play in the local and global carbon
cycle.
Middle Valley
C) We measured rates of carbon fixation
using radioisotopic tracer experiments.
D) Carbon fixation rates were
highest at lower temperatures.
100
Chowder
Hill
Variables: Temp (°C): 4, 25, 50, 90
Chimney type: Structure,
inner vs. outer
nmol C fixed per g per day
Incubation Media: Experimental
50% bottom water
Design:
50% artificial Triplicate incubations
seawater (SO4-free)
Kill control attempted
Sulfate 14 mM
Triplicate subsamples
Sulfide 2 mM pH 6.5
Needles white (Nw)
Needles grey (Ng)
Dead Dog (DD)
Chowder Hill (CH)
10
1
0.1
Questions
•  How do temperature and geochemistry influence rates of
carbon fixation?
0.01
Needles
•  How do rates vary among structures?
Hypotheses
Middle Valley is a sedimented
hydrothermal vent field with many
active anhydrite-hosted chimneys.
This sets it apart from the betterstudied, predominantly sulfide-hosted,
chimneys found elsewhere on the Juan
de Fuca Ridge.
Dead
Dog
•  Outer chimney walls exposed to both sulfide and oxygen will
exhibit higher rates of carbon fixation.
•  Carbon fixation rates will correlate with abundance of
(chemo)autotrophic microbes.
F) Microbial communities were also
strikingly different among the samples.
2412
2405
2398
Max temp
°C
123
260.95
261.04 3.2
7.4
13.1
CO2 (mM)
37.6
365.9
133.2
Estimated
pH
5.98
pH comp.
CO2 [mM]
8.1
δ13C ratio
(permil)
Mineralogy
5.64
14.52
6.06
37.69
0.8
0.8
0.8
0.6
0.6
0.6
0.4
0.4
0.2
0
0
Anhydrite
Anhydrite
Gammaproteobacteria
Epsilonproteobacteria
-25.39 +/- 0.18
Deltaproteobacteria
Betaproteobacteria
Alphaproteobacteria
Anhydrite
unclassified proteobacteria
Thermodesulfovibrio
1
0
Needles
Needles
Dead Dog
Dead Dog
Dead Dog archaea
Chimney
1
1
1
0.8
0.8
0.8
0.8
0.6
0.6
0.6
0.6
0.4
0.4
0.4
total DIC of
seawater media
X X
incubation time
a
109
9
bb cbbM
cbbM
cbbM
cbbM
7
77
710
10
8
1010 7
6
6
10
10
10
10 6
8
8
810
10
10
10
105
10
7
b
4
Chowder
Hill
Chowder
Hill
Dead
Dog
Needles
Needles
Needles
10 4 33
10
103
10
10 4
Dead Dog
Chowder
Hill
Dead Dog
Chowder
Hill
Chowder
Hill
Dead
Dog
0.4
minimal*
Needles archaea
3
4
Dead10
Dog
major carbon
fixation pathways
Needles
Chowder Hill
90
H) Establishing precise drivers of
epi/endolithic carbon fixation
warrants further investigation.
•  The observed rates are not best explained by in situ
geochemistry or microbial community structure at the scale
at which we measured these variables, but finer scale
measurements may offer further insight.
10 5
4
4
10
10
10
Dead
DeadDog
DogHill
Chowder
50
•  In concert with biomass estimates, rates suggest that per cell
carbon fixation rates in chimney deposits may be elevated
over published rates from hydrothermal fluid communities.
10 6
5
10 5
25
Incubation Temperature °C
•  Chemolithoautotrophic microbes adapted to life at cooler
temperatures likely dominate these samples in abundance
and activity.
cbbM
aclB
mcrA
10
5
5
10
10
6
106
5
55
10
10
10
4
44
510
10
1010
aclB
aclB
aclB
aclB
mcrA
mcrA
mcrA
mcrA
6
10 7
10
6
6
10
10
106
10 8
10 8 88
10
8
10
10
b
9a
10
10
9
10
aa bacterial16S
16S
bacterial 16S Bacterial
bacterial
bacterial 16S
16S
16S
archaeal
16S
archaeal
archaeal 16S Archaeal
archaeal 16S
16S
Needles
Needles
Needles
Abundance of 16S rRNA genes and
gene markers representing the
10
Dog
thought toDead
be important
at hydrothermal
10 3
Chowder
Hill
Needles
Dead Dog
Dead Dog
Needles form II is a key
Hill for RuBisCO
vents.
cbbM gene,Chowder
coding
marker for Chowder
the Hill
CBB cycle. aclB (ATP citrate lyase) gene is a key marker for the rTCA
cycle. mcrA (methyl coenzyme-M reductase) is a gene that identifies
Chowder Hill
Dead Dog
Needles
methanogens, all of which use the WL pathway. Gene abundances are
Bacteroidetes
Archaeoglobus
pMC1
Archaeoglobus
pMC1
pMC1
standardized to gram of chimney material from which DNA was
Firmicutes
Thermoprotei
pMC2A384
Thermoprotei
pMC2A384
pMC2A384
Actinobacteria
extracted. Data represent the mean +/- standard deviation of 3 replicate
Thermoplasmata
Korarchaeota
Thermoplasmata
Korarchaeota
Korarchaeota
Chloroflexi
Thermococci
MethanocaldococcaceaeMethanocaldococcaceae
Thermococci
Methanocaldococcaceae
qPCR runs per assay. All differences are significant at p < 0.05 except
Oceanithermus
Cenarchaeum
unclassified Archaea
unclassified
Archaea
Cenarchaeum
unclassified
Archaea
unclassified
for the difference between cbbM and aclB in Needles.
Chowder Hill Archaea
Gammaproteobacteria
Bacteroidetes
Gammaproteobacteria
Bacteroidetes
Archaeoglobus
Epsilonproteobacteria
Epsilonproteobacteria
Firmicutes
Firmicutes
Thermoprotei
Deltaproteobacteria
Deltaproteobacteria
Actinobacteria
Actinobacteria
Thermoplasmata
Betaproteobacteria
Chloroflexi
Betaproteobacteria
Chloroflexi
Thermococci
Alphaproteobacteria
Oceanithermus
Alphaproteobacteria
Oceanothermus
Cenarchaeum
unclassified
unclassified
proteobacteriaunclassified
unclassified
proteobacteria
Bacteria
minimal*
Thermodesulfovibrio
rare*
Thermodesulfovibrio
mass subsample
7
7
10
10
10
10 7
104
0.2
0.2
Chowder Hill
Chowder
Hill
-25.04 +/- 0.24
-26.35 +/- 0.68 no
data
0.4
108
Methanocaldococcaceae
unclassified Archaea
Archaea
1
Archaeoglobus
CH4 (mM)
Oceanithermus
Thermococci
unclassified
Cenarchaeum
minimal*
Bacteria
Archaeoglobus
Depth (m)
Alphaproteobacteria
unclassified proteobacteria
Thermodesulfovibrio
1
1
109
Gene Abundance (copies per gram)
Gene
(copies
pergram)
gram)
GeneAbundance
Abundance (copies
(copies per
per
gram)
Gene
Abundance
5-9m tall
10-40cm wide
Archaeoglobus
Approxima 50cm tall, 30cm
40cm tall
base, 10cm spire
20 cm wide
te size
Chowder
Hill
Proportion of 16S rRNA gene sequences
Dead
Dog
Taxonomic distribution of 16S rRNA gene sequences from 454
pyrosequencing (normalized to 1709 reads for bacteria and 338 reads for
archaea). Archaeal sequencing was unsuccessful with Chowder Hill
material. *Rare includes classified sequences with fewer than 10
Gammaproteobacteria
Bacteroidetes
representatives in each sample
(Aquificae,
Fusobacteria, pMC1
GN02,
Archaeoglobus
Epsilonproteobacteria
Firmicutes
Deltaproteobacteria
Actinobacteria Thermoprotei
pMC2A384
Lentishaerae, MBMPE71, Nitrospirae,
Planctomycetes).
Betaproteobacteria
Chloroflexi and
Thermoplasmata
Korarchaeota
fraction of label
incorporated into biomass
G) Functional genes for different
carbon pathways were enumerated
and also varied among sites.
Gene Abundance (copies per gram)
E) Despite similarities in rates, in situ geochemistry varied greatly
among sites.
Needles
CFX
= rate
4
H14CO3- incubations were conducted shipboard. Rates
were measured from all chimney samples across a
4-90°C temperature gradient. Data represent the mean +/standard deviation of the average value per experimental
treatment. N=3 for each treatment, except in DD and Nw
at 25°C, in which N=2. Blue dots represent the average
of 3 replicate analyses of subsamples from individual
samples. Asterisks represent rate values below detection
limits.
•  Given the increase of carbon fixation at lower incubation
temperatures, the influence of diffuse venting ought to be
considered in the total carbon budget at hydrothermal vents.
•  Molecular techniques targeted at gene activity (e.g. mRNA)
rather than potential (DNA) will help to illuminate the
active carbon fixing organisms and pathways in vent
systems.
Needles
Acknowledgements
Many thanks to members of the Girguis Lab, Dr. Colleen Cavanaugh, Dr.
KT Scott, and the crews of the R/V Atlantis and DSV Alvin for assistance
with sample collection and analysis. Support for this work was provided
by the NSF and NASA.