Differential response of natural phytoplankton communities to enchanced carbon dioxide along the Western Antarctic Peninsula

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OscarSchofield

KayceeColeman

MichaelGarzio

TravisMiles

HughDucklow

Ma?hewErickson

BethanJones

DeboraIglesias-Rodruguez

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Fastestwinterwarmingloca0ononEarth

NorthernWAPperennialiceisgone

87%ofglaciersinretreat

Seaicedura0ondecreasedby~9days

Increaseinoceanheatcontent

YEAR

1992 1994 1996 1998 2000 2002 2004 2006

3.2

3.3

3.4

3.5

3.6

3.7

3.8

Marnsonetal.2008

Qslope

(x109J

m-2)

C

Increaseof6Cinthepast5years

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12%decreaseinchlaoverpast3years,par0cularlynorthern

WAP

197s-198s

1995-25

Montes-Hugoetal.29

ShiRfromlargetosmallphytoplankton

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AtmosphericCO2hasincreased4%since

the18s

Dropof.1pHunit 28%increasein

oceanacidity

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AtmosphericCO2hasincreased4%since

the18s

Dropof.1pHunit 28%increasein

oceanacidity

CO2isprojectedtodoubleby21

(IPCC)

Addi0onaldropof.2-.3pHunits

Equivalentto1-15%increase

inoceanacidity

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Mostoceanacidifica0onstudiestodate

havefocusedonbiocalcifica0onratesin

corals,shellfish,andplanktonicorganisms.

EffectsofenhancedCO2onplanktoncommunitycomposi0on,foodweb

dynamics,andbiogeochemistryremain

largelyunanswered.

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Changeincommunitystructure

Increasedprimaryproduc0vity 100 ppm

380 ppm

800 ppm

Tortell et al.

2008

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LowCO2 HighCO2

Cellular C transport, fixation capacityActive CCMCCM efficiencyEfficiency of DIC utilizationInternal DIC storage

CCMrequirementss0ll

present,butrelaxed,giving

fast-growingspeciesa

compe00veadvantageover

slowergrowingcells

Small cells Large cells

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EffectsofenhancedCO2ondifferentAntarc0cplanktoncommuni0es:1. Largediatomdominatedsystem(MargueriteBay,

SouthernWAP)

Hypothesis:Alargediatom-dominatedcommunitywillrespondposi8velytoenhancedCO2

2. Smalldiatomdominatedsystem(PalmerSta0on,NorthernWAP)

Hypothesis:Dominancewillshi>tolargediatomsinthehighCO2treatmentwhilelowerCO2willfavorsmallcells

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HighChl:12mgm-3 HighProd:23mgCm-3d-1 Diatombloom(mainlypennate):

Cylindrothecasp. Pseudo-nitzschiasp. Chaetocerossp. Thalassiosirasp.

SEMimagesfromB.Jones

LowsurfacepCO2

DatafromT.Takahashi;FigurefromK.Huang

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1-foldincreaseinchla&

produc0vity

NodifferencesbetweenCO2

treatments

2

4

6

8

1

12

14

2 4 6 8 1 12 14 16

5

1

15

2

25

3

354

45

5

2 4 6 8 1 12 14 16

50

40

30

20

10

Chlorophylla(

gL-1)

0

800

400

Prim.

Prod.

(mgC

m-3d

-1)

2 4 6 8 10 12 14 16

Time (days)

00

1200

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2

4

6

2 4 6 8 1 12 14 16

Increaseinchlorophyllbiomassaributedto:- Similarincreasesinnanophytoplankton,picophytoplankton,anddiatoms>2m

60000

40000

20000

0

(cells

mL-1)

2 4 6 8 10 12 14 16

Time (days)

0

NANOPHYTOPLANKTON

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1

2

3

4

2 4 6 8 1 12 14 16

Increaseinchlorophyllbiomassaributedto:- Similarincreasesinnanophytoplankton,picophytoplankton,anddiatoms>2m

4000

3000

2000

0

(cells

mL-1)

2 4 6 8 10 12 14 16

Time (days)

0

PICOPHYTOPLANKTON

1000

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2

4

6

T Tf

Increaseinchlorophyllbiomassaributedto:- Similarincreasesinnanophytoplankton,picophytoplankton,anddiatoms>2m

60000

40000

0

(cells

mL-1) DIATOMS >20 M

20000

"

"

"

" "

()!"**+"

,)-"**+"

.-!"**+"

T14daysT0

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2

4

6

T Tf

Increaseinchlorophyllbiomassaributedto:- Similarincreasesinnanophytoplankton,picophytoplankton,anddiatoms>2m

Chain-formingcentricdiatomChaetocerossp.increasedby22-fold,drivinga3-foldincreaseinthecentric:pennatediatomra0o

NodifferencesbetweenCO2treatments

60000

40000

0

(cells

mL-1) DIATOMS >20 M

20000

"

"

"

" "

()!"**+"

,)-"**+"

.-!"**+"

T14daysT0

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4

8

12

16

2

2 4 6 8 1 12 14 16

.

.2

.4

.6

.8

1.

1.2

2 4 6 8 1 12 14 16

Phospha

te(M)

20

16

12

8

4Nitrate(M)

0

1.0

0.8

0.6

0.4

0.2

0

1.2

2 4 6 8 10 12 14

Time (days)

0

NO3&PO4drawdownbyday1inallmesocosms

NodifferencesbetweenCO2treatments

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HighCO2Largecells

Biomass

Produc0vity

Woulddiatoms

ul0matelybecomenutrientlimited?

N,P,Si,Feuptake

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5

1

15

2

25

3

2 4 6 8 1 12 14

.

.5

1.

1.5

2.

2.5

2 4 6 8 1 12 14 Lowerbiomass&

produc0vityin

highCO2

treatment

Noincreaseinbiomassinhigh

CO2treatment

over0me

* p < 0.05

2.5

2.0

1.5

1.0

0.5Ch

lorophylla(

gL-1)

2 4 6 8 10 12 14

Time (days)

0

0

25

20

15

10

5

0

30

**

* * *

Prim.

Prod.

(mg

C

m-3d

-1)

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15

3

45

6

75

2 4 6 8 1 12 14

5

1

15

2

2 4 6 8 1 12 14

* p < 0.05

3000

1500Nano(cellsmL-1)

0

7500

*

*

* * -84%

2 4 6 8 10 12 14

Time (days)

0

1500

500Pico(cellsmL-1)

2000

-51%0 *

*

1000

4500

6000

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1

2

3

4

5

6

Tpennate Tfpennate Tcentric TfcentricT12days

Diatoms>20

m

(cellsmL-1)

T0 T12daysT00

300

400

200

600

500

Increaseofpennatesandcentricsover0meinlowandambientCO2 NogrowthoflargediatomsinthehighCO2treatment

100

PENNATES CENTRICS

"

"

"

"

"

"

"

"

"

" " " " "

$+!",,-"

&+(",,-"

*(!",,-"

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Nutrientlimita0on?...Doubul

Phosphate=1.8M,Nitrate=25.1M

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Nutrientlimita0on?...Doubul

Saudo-Wilhelmyetal.22

Phosphate=1.8M,Nitrate=25.1M

TypicallyhighFenearPalmerSta0onduetoicemelt,althoughtheseinputscanbeepisodic

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Grazing?...Maybe

Microzooplanktonabundanceandgrazingwereenhancedingreenhousecondi0onsintheNorthAtlan0c

(oseetal.29)

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Non-uniformresponsesofWAPphytoplanktoncommuni0es Posi0veCO2effectonlargediatom-dominatedsystem

LargediatomswereClimited:undersatura0onofsurfacepCO 2 LargediatomsareweaklyregulatedbyCO 2 Eventualnutrientlimita0on?

Lowerbiomass,produc0vity,andphotosynthe0cefficiencyinthehighCO2treatmentofsmalldiatom-dominatedsystem

Oceanacidifica0onalongwithsynergis0cinterac0onsofincreasedtemperatureandshiRstosmallphytoplanktoncouldbedetrimentaltothefoodwebinthe

NorthernWAPregion,resul0nginfurtherdeclinesinhighertrophiclevel

organismssuchasAntarc0ckrill

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/VLaurenceM.Gouldcaptainandcrew

PalmerSta0onlabstaff

PalmerLTE

aytheonPolarServices

UnitedStatesAntarc0cProgram