© Ian Joint Plymouth Marine Laboratory 2011 Ian Joint ([email protected]) Jack Gilbert, Kate Crawfurd &...
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© Ian Joint Plymouth Marine Laboratory 2011 Ian Joint ([email protected]) Jack Gilbert, Kate Crawfurd & Glen Wheeler (PML) Declan Schroeder (MBA) Consequences of ocean acidification for marine microorganisms Both bacteria and phytoplankton
Transcript of © Ian Joint Plymouth Marine Laboratory 2011 Ian Joint ([email protected]) Jack Gilbert, Kate Crawfurd &...
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Ian Joint ([email protected])
Jack Gilbert, Kate Crawfurd & Glen Wheeler (PML)Declan Schroeder (MBA)
Consequences of ocean acidificationfor marine microorganisms
Both bacteria and phytoplankton
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11Presentation Outline
QUESTIONS
Null hypothesis should be that ocean acidification will not affect marine microbes
pH homeostasis
EXPERIMENTAL APPROACHES
Long-term phytoplankton culture at high CO2
Mesocosm experiment on OA
E huxleyi strain differences
16S tag sequencing – how did bacterioplankton respond?
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pH Homeostasis
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11pH Homeostasis
PH OF SEAWATER IS NOT CONSTANT
Phytoplankton blooms may increase pH by >0.4 pH units
Freshwater lakes are poorly buffered
BACTERIA & PHYTOPLANKTON REGULATE INTERNAL PH
This explains how pathogenic bacteria can survive stomach pH of <1.
Acidophilic Chlamydomonas – energetics of growth at pH 2 rather than pH 7
A 7% increase in ATP requirement
(Messerli et al. 2005. J Exp Biol, 208, 2569-2579)
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11pH of freshwater lakes
Lakes are much less buffered than the oceans
They experience large daily variations in pH - as much as 2-3 pH units (e.g. Maberly et al., 1996).
Variations in pH also occur over very small distances. Talling (2006) showed that in some English lakes, pH could change by > 2.5 pH units over 14 m depth
Yet phytoplankton, bacteria and archaea are all present in lakes, and appear to be able to accommodate large daily and seasonal changes in pH.
Are marine microbes different from freshwater, with less ability to acclimate and adapt?
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Many bacteria accommodate low pH
Stomach pH is 1-3
Bacteria can pass through and survive this pH challenge (e.g. Campylobacter & pathogenic E. coli)
Survival is possible because bacteria have proton pumps to remove H+
One mechanism is uptake of arginine and release of decarboxylation product (Fang et al, 2009).
Maintain intracellular pH at 5
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Null hypothesis
I suggest that the Null hypothesis should be – non-calcifying microbes will not be affected by OA
Joint, I, Doney S.C., Karl, D.M. (2011) Will ocean acidification affect marine microbes? ISME Journal. 5, 1-7
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Long-term diatom culture experiments
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0 1 2 3 4 57.5
8.0
8.5
9.0
9.5
0
1
2
3
4
Time (d)
pH
Cel
ls x
106
ml-
1
Cell number
pH
pH changes rapidly in culture
Kate Crawfurd
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11T. pseudonana – maintained for >100 generations
7.6
8.0
8.4
8.8
9.2
0 2 4 6 8 10 12
Time (weeks)
pH
Kate Crawfurd
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11What changed after 100 generations?
Change in -
C:N ratio - slightly decreased
Red fluoresence (= chlorophyll) - slightly increased
No change in -
Cell size or morphology
Photosynthetic efficiency (Fv/Fm)
Functional cross section of PSII (σPSII)
RuBisCO expression (rbcS)
Kate Crawfurd
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One ∂-carbonic anhydrase (∂-CA4) was up-regulated in the high CO2 cultures (p=0.005).
Neither rbcS nor 3 other ∂-CAs had altered expression.
T. pseudonana after 3 months
Red fluorescence Fv/Fm C:N
760 µatm CO2 235±4 0.62±0.01 6.40±0.40*
380 µatm CO2 251±23 0.60±0.02 5.96±0.12*
Kate Crawfurd
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11Only CA4 expression different
2
1
0.5
0.25
0.125
0.063
CA4 CA5 CA6 CA7 rbcS
Rel
ativ
e ex
pres
sion
(hi
gh C
O2
: pr
esen
t da
y C
O2)
Kate Crawfurd
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11Evidence for acclimation or
adaptation
3 months at 760 µatm CO2
To 760 µatm CO2
To 760 µatm CO2
To 380 µatm CO2
To 380 µatm CO2
3 months at 380 µatm CO2
Kate Crawfurd
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11Acclimation or adaptation?
No statistically significant change in -
Cell size or morphology
C:N ratio
Red fluorescence
Photosynthetic efficiency (Fv/Fm)
Functional cross section of PSII (σPSII)
RuBisCO expression (rbcS)
CA expression (CA4, CA5, CA6 or CA7)
Kate Crawfurd
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11C:N content
No significant differences between means of the four conditions. Global test ANOSIM (R=0.03)
0
2
4
6
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HL LL HH LH
C:N
Kate Crawfurd
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Phytoplankton laboratory experiments summary
We overcame changing pH by using low biomass cultures
No different detected in specific growth rate of T. pseudonana in CO2 treatments
Adaptation not detected after 100 generations
Some up-regulation of ∂CA4 but not other CAs or rbcs
T. pseudonana acclimates to 760 µatm CO2
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Mesocosm Experiments
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0
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09-May 10-May 11-May 12-May 13-May 14-May 15-May 16-May
Flu
ore
sc
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ce
(a
rbit
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un
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7.7
7.8
7.9
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8.1
pH
Microbial growth changes the environment
pHBiomass
Ian Joint
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Nutrients added
CO2 added
CO2 added
pH during experiment
7.6
7.8
8
8.2
8.4
30-Apr 07-May 14-May 21-May 28-May
pH
760 µatm CO2
380 µatm CO2
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11Chlorophyll fluorescence
0
5
10
15
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30-Apr 07-May 14-May 21-May 28-May
Arb
itrar
y un
its
High CO2
Present day
CO2 added
CO2 added
760 µatm CO2
380 µatm CO2
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11Primary Production
8-May 9-May 10-May 11-May 12-May 13-May 14-May 15-May0
200
400
600
800
1000
1200
mg
C m
-2 d
-1
High CO2
Present day CO2
}}
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0.0E+00
1.0E+03
2.0E+03
3.0E+03
4.0E+03
30-Apr 07-May 14-May 21-May 28-May
Cel
ls m
l-1
High CO2
Present day
Coccolithophore number
760 µatm CO2
380 µatm CO2
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Different E huxleyi strains were present
Genotype ‘D’ reduces in abundance during bloom at 760 µatm CO2
No significant change in genotype ‘B’ throughout bloom at 380 µatm CO2
Genotype ‘C’ did not change in either treatment Genotype ‘A’ slight positive selection BUT it’s not
significant.
E huxleyi has different, distinguishable genotypes, although they all look the same.
They respond differently to pCO2 change
E huxleyi appeared to grow less well in this experiment at high CO2 and WAS NOT REPLACED BY ANY OTHER PHYTOPLANKTON
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Bacterial response to OA
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11Numbers of bacteria
CO2 added
Pyrosequencing
0.0E+00
4.0E+06
8.0E+06
1.2E+07
1.6E+07
30-Apr 07-May 14-May 21-May 28-May
Ce
lls m
l-1
760 µatm CO2
380 µatm CO2
CO2 added
Pyrosequencing
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11English Channel - High throughput sequencing
Jack Gilbert
Bacterial diversity determined using 16S rDNA V6 tag pyrosequencing (Sogin et al., 2006)
Over 10 million sequences Over 20,000 genotypes detected Small number of taxa dominated The most abundant organisms were a strain of
SAR11 (Rickettsiales) and Rhodobacteriales
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Conclusions
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11Is “Null hypothesis”
supported?
T. pseudonana showed acclimation to high CO2 but no adaptation after 100 generations
E. huxleyi production lower under high CO2 but we have demonstrated that there are different genotypes that dominate during a bloom
10 million bacterial 16S sequences revealed no effect of CO2 treatment throughout a 3 week mesocosm experiment
Both 16S tag sequencing and metatranscriptomics study revealed that the largest differences were with time (bloom effect) rather than with treatment (ocean acidification)
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NERC for funding the Aquatic Microbial Metagenomics consortium
NERC Environmental Bioinformatics Centre – Dawn Field
Royal Society Travel Grant
Acknowledgements
