Plankton stoichiometry and ocean change
Impacts of Ocean Change on Primary Producers
Ulf Riebesell
Joana Barcelos e Ramos, Antje
Klaus von Bröckel, Jan Czerny,
UlfBiermann,
Riebesell
Arne Körtzinger, Sebastian Krug, Michael Meyerhöfer, Marius Müller, Andreas Oschlies,
Leibniz Institute of Marine Sciences, IFM-GEOMAR, Kiel
Kai Schulz, Julia Wohlers, Eckart Zöllner
SOPRAN Mesocosm CO2 perturbation experiment, Baltic Sea, July 2008
Foto: Mesocosm Facility, University of Bergen, Norway
CarboOcean
For primary producers the ocean in a high CO2 world will be different
from the present ocean in several respects
Atmospheric CO2
Climate
Ocean acidification
Seawater
CO2
Ocean warming
Temperature
Mixing,
Circulation
stratification
Carbonate
chemistry
Light
Atmospheric
deposition
Nutrients
Ocean
biota
Pelagic
ecosystems
Stoichiometry
Rain ratio
(Si/C/N/P/Fe)
(CaCO3/POC)
C-partitioning Nutrient utilization
(POC-DOC-TEP)
efficiency
Carbon sinks & sources
Impacts of Ocean Change on Primary Producers
Atmospheric CO2
Overarching questions:
• Will the future ocean be more or less
productive?
• Will primary producers provide more
Climate
Seawater
CO2
Temperature
Carbonate
chemistry
Light
less CO2?
Atmospheric
deposition
Nutrients
Pelagic ecosystems
Ocean biota
or less food to higher trophic levels?
• Will marine biota sequester more or
Mixing,
Circulation
stratification
Stoichiometry
Rain ratio
C-partitioning
Nutrient utilization
efficiency
Carbon sinks & sources
Assess OA- and T-driven feedbacks according to
Sign of change positive feedback
negative feedback
amplifies initial perturbation
dampens initial perturbation
Sensitivity
level of perturbation needed to trigger a feedback
Capacity
strength of feedback compared to initial perturbation
Longevity
relevant time-scales: permanent vs. transient
Responses to ocean acidification/carbonation
There will be winners and losers
Winners
Eelgrass (Zostera)
Cyanobacteria
Dinoflagellates
Filamentous green algae
Losers ?
Coccolithophores
Hinga 2002
pH range for maximum growth
Responses to ocean acidification/carbonation
Feedback sign
Calcification
Sensitivity
Capacity
Longevity
e.g. calcareous microalgae
+ weak
++ moderate
• Decrease in calcification, slight
+++ strong
present
pCO2
increase in photosynthesis
photosyn.
Riebesell et al. 2000, Zondervan et al. 2001,
Sciandra et al. 2003, Delille et al. 2005, Leonardos &
Geider 2005, Langer et al. 2006, Feng et al. 2008,
Krug et al. unpubl., Müller (talk tomorrow)
calcific.
Gephyrocapsa oceanica
1 μm
Calcidiscus quadriperforatus
Coccolithus braarudii
pCO2
Responses to ocean acidification/carbonation
Feedback sign
Calcification
negative
Sensitivity
Capacity
Longevity
e.g. calcareous
microalgae
+
+
• Decrease in calcification, slight
?
∆CaCO3 export
increase in photosynthesis
Riebesell et al. 2000, Zondervan et al. 2001,
Sciandra et al. 2003, Delille et al. 2005, Leonardos &
Geider 2005, Langer et al. 2006, Feng et al. 2008.
Krug et al. unpubl., Müller (talk tomorrow)
∆pCO2atm
• Declining strength of carbonate
pump increases CO2 sequestration,
but only weak feedback
Zondervan et al. 2001, Heinze 2004,
Ridgwell et al. 2007, Gehlen et al. 2007
• Open question: Replacement of
sensitive species by more robust
coccolithophorids or by other groups?
see Krug et al. M28
Heinze 2004
Ridgwell et al. 2007:
60-200 PgC until year 3000
corresponding to ∆pCO2~15-49 ppm
Responses to ocean acidification/carbonation
Feedback sign
Ballast effect
positive
Sensitivity
Capacity
Longevity
e.g. calcareous
microalgae
?
+++
+++
Klaas & Archer 2002
• POC flux correlates closest
with CaCO3 flux
Decreased calcification
Present CO2
High CO2
decrease deep flux of POC
CaCO3
POC
• Reduced calcification may
POC
• CaCO3 serves as ballast
CaCO3
Klaas & Archer 2002, Francois et al. 2002,
Armstrong et al. 2002, but see Passow 2004
Responses to ocean acidification/carbonation
Feedback sign
Stoichiometry
negative
Sensitivity
Capacity
Longevity
e.g. calcareous microalgae
• Enhanced drawdown of C vs. N and P
Riebesell et al. 2007
• Enhanced C loss from upper layer
also Delille et al. 2005
• Mechanism still unclear
present CO2
2xCO2
3xCO2
C/N=6.0
C/N=7.1
C/N=8.0
Riebesell et al. 2007
Responses to ocean acidification/carbonation
Feedback sign
Stoichiometry
negative
Sensitivity
Capacity
Longevity
e.g. calcareous
microalgae
++
++
• Enhanced drawdown of C vs. N and P
Riebesell et al. 2007
• Enhanced C loss from upper layer
C:N=const.
C:N=f(pCO2)
Export production
Delille et al. 2005
• Mechanism still unclear
• Low to moderate capacity until 2100
Oschlies et al. 2008, see also Matear & McNeil T32
Int(del EP)
Int(del C storage)
Carbon storage
Oschlies et al. 2008
++
Responses to ocean acidification/carbonation
Capacity
• Enhanced exudation at
750
ppmv CO2
500
400
300
(µg Xanthan Equiv. L-1)
Transparent Exopolymer Particles
elevated CO2, leading to
enhanced TEP formation
Longevity
e.g. calcareous microalgae
190
Extracellular Corg
Sensitivity
380
Feedback sign
Baltic Sea
natural community
200
100
Engel (2002)
0
700
500
Emiliania huxleyi
lab culture
300
Heemann et al. (unpubl.)
100
0
20
40
60
CO2 (µmol L-1)
80
100
Responses to ocean acidification/carbonation
Feedback sign
Extracellular Corg
negative
• Enhanced exudation at
Sensitivity
Longevity
e.g. calcareous
microalgae
++
+++
Present CO2
elevated CO2, leading to
enhanced TEP formation
•
Capacity
Accelerating aggregation
and sinking of organic
matter
Engel et al. 2004,
Schartau et al. 2007
• Uncertainties: longevity
(transient responses?)
Arrigo (2007)
?
High CO2
Responses to ocean acidification/carbonation
Feedback sign
Capacity
Longevity
e.g. calcareous microalgae
glacial
present
Nitrogen fixation
Sensitivity
Trichodesmium (diazotrophic cyanobaterium)
• Enhanced N2 fixation by
Trichodesmium
Hutchins et al. 2007, Barcelos e Ramos et al. 2007,
Levitan et al. 2007
•Common phenomenon among all
diazotrophs? See Czerny et al. T11
Hutchins et al. 2007
projected 2100
Responses to ocean acidification/carbonation
Feedback sign
Sensitivity
Capacity
e.g. calcareous microalgae
Nitrogen fixation
Trichodesmium (diazotrophic cyanobaterium)
• Enhanced N2 fixation by
Trichodesmium
Barcelos e Ramos et al. 2007,
Hutchins et al. 2007, Levitan et al. 2007
• Common phenomenon among all
diazotrophs? See Czerny et al. T11
Barcelos e Ramos et al. 2007
Longevity
Responses to ocean acidification/carbonation
Feedback sign
Sensitivity
Capacity
e.g. calcareous microalgae
Nitrogen fixation
N:P
Trichodesmium (diazotrophic cyanobaterium)
C:P
• Enhanced N2 fixation by
Trichodesmium
Barcelos e Ramos et al. 2007,
Hutchins et al. 2007, Levitan et al. 2007
• Common phenomenon among all
C:N
diazotrophs? See Czerny et al. T11
Barcelos e Ramos et al. 2007
Longevity
Responses to ocean acidification/carbonation
Feedback sign
Nitrogen fixation
negative
Sensitivity
Capacity
++
+
Longevity
?
C:N=f(pCO2).
C:N=f(pCO2)
+ N2fix=g(pCO2)
Trichodesmium (diazotrophic cyanobaterium)
• Enhanced N2 fixation by
Trichodesmium
Barcelos e Ramos et al. 2007,
Hutchins et al. 2007, Levitan et al. 2007
Oschlies et al. unpubl.
• Common phenomenon among all
~ 6 PgC until 2100
diazotrophs? See Czerny et al. T11
• Low capacity (model assumes shallow remineralisation)
(feedback kills itself: enhanced N2 fixation  more DIN  reduced N2 fixation
does Tricho-derived org. matter sink?
Responses to ocean warming
Feedback sign
Nutrient supply
Sensitivity
++
• Reduced mixing,
lower nutrient supply,
decreased productivity
e.g. Bopp et al. 2001, Boyd &
Doney, 2002, Sarmiento et al.
2004, Schmittner et al. 2008,
Schneider et al. 2008
Schneider et al. 2008
Capacity
±0
Longevity
++
Responses to ocean warming
Feedback sign
Nutrient supply
Nut. utiliz. efficiency
negative
• Reduced mixing,
lower nutrient supply,
decreased productivity
e.g. Bopp et al. 2001, Boyd &
Doney, 2002, Sarmiento et al.
2004, Schmittner et al. 2008,
Schneider et al. 2008
• Reduced mixing,
increased light availability,
increased productivity
Doney 2006
Sensitivity
Capacity
Longevity
+++
++
±0
++
++
++
++
Responses to ocean warming
Feedback sign
Sensitivity
Capacity
Longevity
Auto- vs.heterotrophy
• Expected: bacterial degradation
DIC/DIN/DIP
increases stronger than primary
production
Q10 = rate increase for 10°C
temperature increase
1<Q10<2
2<Q10<3
Phytoplankton
Zooplankton
1<Q10<2
DOM
Bacteria
2<Q10<3
Temperatures:
ambient
+2°C
+4°C
+6°C
Kiel in-door mesocosms
Detritus
Sinking
Responses to ocean warming
Feedback sign
Auto- vs.heterotrophy
positive
Sensitivity
Capacity
++
• Expected: bacterial degradation
increases stronger than primary
production
∆DIC etc. = absolute change in pool size
Red arrows = temp. - sensitive processes
++
P
∆ DOC
∆ DOC
E
P
R
A
E
∆ POC
∆ POC
++
• Observed: enhanced
community respiration (R),
DOC exudation (E),
TEP formation (A)
decreased sinking (S)
 decreased DIC drawdown
ambient temp.
∆ DIC
∆ DIC
Longevity
elevated temp.
A ∆ DIC
∆ DIC
E
P
P
∆ DOC
∆ DOC
E
A
∆ POC
∆ POC
R
S
S
R
Thermocline
Thermocline
Wohlers et al. subm.
R
S
S
A
Responses to ocean warming
Feedback sign
Nutrient inventories
?
Sensitivity
?
Capacity
++
Longevity
+++
• Decreased deep ocean
ventilation expands oxygen
minimum zones (OMZ)
Matear & Hirst 2003
• Decreases N inventory due to
denitrification and anammox
• Increases P and Fe release
from anoxic sediments
Impacts of Ocean Change on Primary Producers
Responses to ocean acidification/carbonation
Feedback sign
Sensitivity
Capacity
Longevity
Calcification
negative
+
+
?
Ballast effect
positive
?
+++
+++
Stoichiometry
negative
++
++
++
Extracellular Corg
negative
++
+++
?
Nitrogen fixation
negative
++
+
?
(Trace) nutr. speciation
presentations by H. de Baar and E. Breitbarth (yesterday)
Production of CR gases see presentation by F. Hopkins (tomorrow)
Responses to ocean warming
Feedback sign
Nutrient supply
Nutr. utiliz. efficiency
Nutrient inventory
Auto- vs. heterotrophy.
Sensitivity
Capacity
Longevity
+++
±0
++
negative
++
++
+++
?
?
++
+++
positive
++
++
++
Impacts of Ocean Change on Primary Producers
Responses to ocean acidification
Feedback sign
Calcification
negative
Ballast effect
positive
Stoichiometry
negative
Extracellular Corg
negative
Nitrogen fixation
negative
Overarching questions:
• Will the future ocean be more or
less productive?
Less in low latitudes, more in high
latitudes
• Will primary producers provide
more or less food to higher
trophic levels?
Responses to ocean warming
Feedback sign
Nutrient supply
Nutr. utiliz. efficiency
Nutrient inventory
Auto- vs. heterotrophy.
Probably less (higher turnover in
microbial loop), less nutritious
• Will marine biota sequester more
or less CO2?
negative
?
positive
Possibly more, may partly
compensate for decrease in
physical carbon pump
Impacts of Ocean Change on Primary Producers
Major uncertainties
• Short-term (stress) vs. acclimated responses
• Species (strain)-specific differences
• Synergetic effects with other stressors (e.g. warming)
• Single species vs. community level responses
• Physiological and genetic adaptation
• Species replacement vs. loss of ecosystem functionality