Phytoplankton in a high-COPhytoplankton in a high-CO22 world: world:

biological responses and their biological responses and their

biogeochemical implicationsbiogeochemical implications

Ulf Riebesell

Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR) Kiel University, Germany

Potential drivers in a high-COPotential drivers in a high-CO22 world world

Atmospheric COAtmospheric CO22

Mixing,Mixing,stratificationstratification

CirculationCirculation

LightLight NutrientsNutrients

Carbon sinks & sourcesCarbon sinks & sources

Oceanic COOceanic CO22

CarbonateCarbonatechemistrychemistry

Global warmingGlobal warming

Surface ocean Surface ocean temperaturetemperature

Nutrient utilizationNutrient utilizationefficiencyefficiency

AtmosphericAtmosphericdust dust (Fe)(Fe)

PrecipitationPrecipitation

Ocean biotaOcean biota

WindWindstressstress

Rain ratioRain ratio(CaCO(CaCO33/C/Corgorg))

StoichiometryStoichiometry(Si/C/N/P/Fe)(Si/C/N/P/Fe)

Criteria for evaluatingCriteria for evaluatingthe biogeochemical relevance of feedbacksthe biogeochemical relevance of feedbacks

Sign of changeSign of changepositive feedback positive feedback amplifies initial perturbationamplifies initial perturbationnegative feedbacknegative feedback dampens initial perturbationdampens initial perturbation

SensitivitySensitivitylevel of perturbation needed to trigger a feedbacklevel of perturbation needed to trigger a feedback

CapacityCapacitystrength of feedback compared to initial perturbationstrength of feedback compared to initial perturbation

LongevityLongevityrelevant time-scales: permanent vs. transientrelevant time-scales: permanent vs. transient

Today‘s worldToday‘s worldpCOpCO22: 280-380 ppmV: 280-380 ppmV

High-COHigh-CO22 world worldpCOpCO22: 580-720 ppmV: 580-720 ppmV

Emiliania huxleyiEmiliania huxleyi

Gephyrocapsa Gephyrocapsa oceanicaoceanica

Calcidiscus leptoporusCalcidiscus leptoporus

CO2-Calcification feedback

0

50

100

150

200

250

300

350

400

0 200 400 600 800 1000

Calc

ite c

onte

nt

(pg p

er

cell)

ppCOCO22 (µatm) (µatm)

Coccolithus pelagicusCoccolithus pelagicus

BUT !BUT !

CO2-Calcification feedback

10m

S=31.3S=29.8

S=31.3

Sediment Trap

pump

COCO22 regulation regulation

95% PAR95% PAR• 190 ppmV• 370 ppmV• 700 ppmV

190190370370

700700

pCOpCO22 (ppmv)(ppmv)

Large Scale Facilities, Bergen, NorwayLarge Scale Facilities, Bergen, Norway

Plankton development under Plankton development under

past, present and future COpast, present and future CO22

(Mesocosm experiments in 2000 and 2003)(Mesocosm experiments in 2000 and 2003)

5m

pCO2 normalised

0 5 10 15 200

200

400

600

800

Day

µatm

0

2

4

6

8

10

12

14

0 5 10 15 20

Chlorophyll a

pCO2 (normalized)ppm

Vµ

g L

-1Year 2100PresentLGM

Mesocosm experimentMesocosm experimentBergen 2000Bergen 2000

Emiliania huxleyiEmiliania huxleyi

Initial nutrient concentrations:Initial nutrient concentrations: NONO33

-- 15.5 mmol m 15.5 mmol m-3-3

POPO443-3- 0.51 mmol m 0.51 mmol m-3-3

Si(OH)Si(OH)44 ~0 ~0

NONO33-- and PO and PO44

3-3- exhausted on day 13 exhausted on day 13

B. Delille et al., in prep.B. Delille et al., in prep.

Primary production and calcification during a bloom of Primary production and calcification during a bloom of Emiliania huxleyiEmiliania huxleyi

Calcification

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)Production

Dissolution

Respiration -10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d2

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d4d3

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)d10

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d11

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d12

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d13

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

) d14

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

) d15

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)d18

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d21-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d21-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d21-10

10

20

30

(µmolC.kg-1.d-1)

(µm

olC

.kg-1

.d-1

)

d23

B. Delille et al. in prep.B. Delille et al. in prep.

CO2-Calcification feedback

10 20 30

-10

10

20

30

d11

d13

d15

d17

d2

d7

d23

(µm

olC

.kg-1

.d-1

)

d11

d13

d15

d17

d23

d2

d7

d11

d13

d15d17

d23

d7

d2

d11

d13

d15

d17d2

d7

d23

d11

d13

d15

d7

d23

d2

10 20 30-5

-10

10

20

30

d11

d13

d15 d17

d23

d7

(µmolC.kg-1.d-1)

10 20 30-5

d7

d11

d13

d15

d23

(µmolC.kg-1.d-1)

10 20 30-5

d11

d13

d15d17

d2

d7

d23

(µmolC.kg-1.d-1)

Year 2100(700 ppmV)

Present(370 ppmV)

LGM(190 ppmV)

Calcification

Pro

du

cti

on

Resp

ir.

Dissol.

-10

10

20

30

d11

d13 d15

d17

d19

d21

d2

d9

(µm

olC

.kg-1

.d-1

)(µ

mol

C.k

g-1.

d-1)

B. Delille et al. in prep.B. Delille et al. in prep.

-10

10

20

30

d11

d13

d15

d17

d2

d7

d23

(µm

olC

.kg-1

.d-1

)

10 20 30-5

-10

10

20

30

d11

d13

d15 d17

d23

d7

(µmolC.kg-1.d-1)

Year 2100(700 ppmV)

Present(370 ppmV)

LGM(190 ppmV)

Calcification

Pro

du

cti

on

Resp

ir.

Dissol.

-10

10

20

30

d11

d13 d15

d17

d19

d21

d2

d9

(µm

olC

.kg-1

.d-1

)(µ

mol

C.k

g-1.

d-1)

B. Delille et al. in prep.B. Delille et al. in prep.

Increasing pCOIncreasing pCO22 from from

190 ppmV to 700 ppmV caused190 ppmV to 700 ppmV caused

24-48 h delay in the 24-48 h delay in the onset of calcificationonset of calcification

40% decrease in 40% decrease in CaCOCaCO33 production production

Atmospheric COAtmospheric CO22

EcosystemEcosystem

pH, pH, Ca COCa CO33

Rain ratioRain ratio

Bio-Bio-calcificationcalcification

FunctionalFunctionalgroupsgroups

EnvironmentEnvironment

BiogeochemistryBiogeochemistry

Surface ocean alkalinitySurface ocean alkalinity

Loop with Loop with eveneven number of negative influences: number of negative influences: positive feedbackpositive feedback oddodd number of negative influences: number of negative influences: negative feedbacknegative feedback

CO2-Calcification feedback

negative influencepositive influence Sign of change

negative feedback (dampens initial perturbation)

Sensitivity high

Capacity low (6-30 Gt C until 2100

for 20-40% decrease)

Longevity permanent vs. transient ?

pCO2 (ppmV)

100

200

300

400

500

600

700

00 02 04 06 08 10 12 14 16 18day

Chlorophyll a

ppm

Vµ

g L

-1

0

1

2

3

4

5

1 3 5 7 9 11 13 15 17 19 21

Year 2100PresentLGM

pCO2 (normalized)

Chlorophyll a

Initial nutrient concentrations:Initial nutrient concentrations: NONO33

-- 8.0 mmol m 8.0 mmol m-3-3

POPO443-3- 0.5 mmol m 0.5 mmol m-3-3

Si(OH)Si(OH)44 12.0 mmol m 12.0 mmol m-3-3

NONO33-- exhausted on day 12 exhausted on day 12

Mesocosm experimentMesocosm experimentBergen 2003Bergen 2003

Year 2100: Diatoms > Dinophyceae (> Coccolithophores)

Present: Coccolithophores > Diatoms (> Dinophyceae > Chlorophyceae)

LGM: Diatoms (> Dinophyceae > Coccolithophores)

B. Delille, unpubl.B. Delille, unpubl.

2003 Mesocosm CT

1800

1850

1900

1950

2000

2050

2100

3 8 13 18 23

Day in May

CT m

mo

l.kg

-1

R. Bellerby et al., unpubl.

biologicalcarbonfixation

0 2 4 6 8 10 12 14 16 18 20

Day

DIC

(

µm

ol kg

-1)

Dissolved inorganic carbon

Year 2100

Present

LGM

Carbon over-production feedback

-20

0

20

40

60

80

100

1 3 5 7 9 11 13 15 17 19 21

Year 2100

Present

LGM

Day

Carb

on loss

(

µm

ol kg

-1)

Carbon loss = ∆DIC - ∆TPC - ∆DOC

Carbon over-production feedback

Transparent Exopolymer ParticlesTransparent Exopolymer Particles

Dissolved Polysaccharides

Cell density

Day

DOCDOC

Low COLow CO22 High COHigh CO22

DOCDOC

TEPTEP

Marine snowMarine snow

ExportExport

ExsudationExsudation

Sign of change negative feedback

Sensitivity ?

Capacity high

Longevity permanent vs. transient ?

Carbon over-production feedback

Engel et al. 2004 Nature 428, 929Engel et al. 2004 Nature 428, 929

FACE (Free Air CO2 Enrichment) Program

- with worldwide 33 experimental sites

- 16 sites in Europe

Research needs:Research needs:

Observational studies on combined COObservational studies on combined CO22 and T- and T-effectseffects - assess biological responses - assess biological responses

- unravel biogeochemical processes- unravel biogeochemical processesand potential feedbacksand potential feedbacks

through a suite of perturbation studiesthrough a suite of perturbation studies- laboratory experiments- laboratory experiments- mesocosm studies- mesocosm studies- open ocean CO- open ocean CO22 fertilization experiment fertilization experiment