Coral and foraminifera calcification mechanisms in view · PDF fileCoral and foraminifera...

Coral and foraminiferacalcification mechanisms in view of

high CO2 ocean (Monaco 2008)

Jonathan ErezInstitute of Earth Sciences,

The Hebrew University of Jerusalem Israel.

Shmuel Bentov, Jack Silverman, Kenny Schneider, Alon Braun, Mor Grinstein and Boaz Lazar

Funding: BSF, BMBF, ISF, GIFCooperation: MIT, MPI-Bremen, IFM Kiel

Introduction and questions

• Ocean acidification is well documented in terms of Ώ or CO3

2-, past, present, and future (Orr, Feely, Kleypas, Caldeira, Tyrell and others)

• However, calcifying organisms are not little pieces of CaCO3 floating in the ocean. “they are protected by membranes”, so why are they sensitive to Ώ?

• Why is there a different response in different organisms? If we ignore experimental artifacts, why some respond strongly and other do not?

• More specifically: the calcification response of foraminifera and corals is different from that of coccolithophores why is that?

• Environmental variability in carbonate chemistry of ambient seawater (diurnal and seasonal) is larger then ocean acidification, so why are they responding to changes of 0.2 pH units or less?

Introduction and questions 2

A plate from the book of Winter and Seisser on Coccolithophores

Red Sea Photo: C. Hemleben Tubingen

1. The most diverse and most productive ecosystem in the oceans

2. Precipitate ~ 50 % of the net CaCO3 accumulation in the ocean

3. Coral skeletons provide excellent oceanic paleo-archives

Coral Reefs

Photo: C. Veronbook

Riebesell et al.2000, Nature

C. leptoporus C. pelagicus

Langer et al. 2006 G3

M. Debora Iglesias-Rodriguez, et al.Science, 2008

Foraminifera and corals are major CaCO3producers in the ocean. Both groups show light

enhanced calcification suggesting that symbionts are involved.

Constant CT experiment

7.8 8.0 8.2 8.4 8.6-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

7.8 8.0 8.2 8.4 8.6-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

G

(µm

ol C

aC

O 3 ml-1

cora

l h-1)

pH

Dark

Light

100 200 300 400 500-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

100 200 300 400 500

0

2

G

(µm

ol C

aC

O 3 ml-1

cora

l h-1)

CO3

-2 (µmol kg-1

S.W)

Dark

Light

Schneider and Erez , 2006 Limnol &Oceanog

Calcification response to changes in the Calcification response to changes in the carbonate systemcarbonate system

100 200 300 400 500-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

100 200 300 400 500-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

G

(µm

ol C

aC

O 3 ml-1

cora

l h-1)

CO3

-2 (µmol kg-1

S.W)

A

Light

Dark

150 200 250 300 350 400

-0.3

0.0

0.3

0.6

0.9

150 200 250 300 350 400

-0.3

0.0

0.3

0.6

0.9

CO3

-2 (µmol kg-1

S.W)

G

(µm

ol C

aC

O 3 ml-1

cora

l h-1) B

Light

Dark

CONSTANT pCO2CONSTANT pH


Summary of Constant temperature experiments

CO32- (µmol kg-1)

100 200 300 400 500

Cal

cific

atio

n ra

te ( µ

mo

l CaC

O 3 cm

-2 h

-1)

-0.5

0.0

0.5

1.0

Ωarag

1 2 3 4 5 6 7 8

a b

LightDark

Y = 1.1 x 10-3X - 2.4 x10-2

R2 = 0.30

Y = 1.3 x 10-3X - 0.26R2 = 0.54

Y = 7.8 x 10-2X - 2.4 x10-2

R2 = 0.30

Y = 8.9 x 10-2X - 0.26R2 = 0.54

CO32- (µmol kg-1)

100 200 300 400 500

Cal

cific

atio

n ra

te ( µ

mo

l CaC

O 3 cm

-2 h

-1)

-0.5

0.0

0.5

1.0

Ωarag

1 2 3 4 5 6 7 8

a b

LightDark

Y = 1.1 x 10-3X - 2.4 x10-2

R2 = 0.30

Y = 1.3 x 10-3X - 0.26R2 = 0.54

Y = 7.8 x 10-2X - 2.4 x10-2

R2 = 0.30

Y = 8.9 x 10-2X - 0.26R2 = 0.54

Schneider and Erez, L&O (2006)

Decoupling of photosynthesis from calcificationConstant CConstant CTT Constant pCOConstant pCO22

Constant pH

7.8 8.0 8.2 8.4 8.6-3

-2

-1

0

1

2

3

4

5

7.8 8.0 8.2 8.4 8.6

-2

0

2

4

7.8 8.0 8.2 8.4 8.6

-2

0

2

4

Oxy

gen

Flu

x

(µm

ol O

2 ml-1

cora

l h-1)

pH1500 1800 2100 2400 2700-2

-1

0

1

2

3

1500 1800 2100 2400 2700-2

-1

0

1

2

3

1500 1800 2100 2400 2700-2

-1

0

1

2

3

Oxy

gen

Flu

x

(µm

ol O

2 ml-1

cora

l h-1)

CT (µmol kg-1)

RR

PNPN

1000 1500 2000 2500 3000-3

-2

-1

0

1

2

3

4

1000 1500 2000 2500 3000-3

-2

-1

0

1

2

3

4

1000 1500 2000 2500 3000-3

-2

-1

0

1

2

3

4

Oxy

gen

Flu

x

(µm

ol O

2 ml-1

cora

l h-1)

CT (µmol kg-1)

R

PN

PG

PG

PG


-1

-0.5

0

0.5

1

1.5

2

2.5

3

7.8 7.9 8 8.1 8.2 8.3 8.4 8.5 8.6

pH

Cal

cific

atio

n (µ m

ole

CaC

O 3h-1

ml c

oral-1

Light

Dark

CO2

Acropora Sp. Laboratory Experiments at constant CTT


Calcification Using internal pH (light + 0.2, dark -0.3 pH units)

y = 1.667x - 12.918

R2 = 0.6787

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

7.40 7.60 7.80 8.00 8.20 8.40 8.60 8.80

internal pH

Cal

cific

atio

n (D

ark

and

Ligh

t)


Live Globigerinoidessacculifer and its symbiontic algae

(Dinoflagellates)

planktonic foraminifera response to ocean acidification

Russel et al. 2004

G. ruber (at 27ºC and 35 psu)

0.0

1.5

3.0

4.5

7.9 8.1 8.3 8.4

pH

Av.

cal

cific

atio

n ra

te (

µµ µµg/

day)

Data of B. Kisakurek project Cassiopea, EC

Constant CT, variable pH

A. lessonii

A. lobifera

Constant CT, variable pHErez 2003

Total

CaCO3

Skeleton

Photosynthesis

Foraminifera Miliolids

Erez 2003

Growth of Amphistegina at constant pH (8.15) with variable C T

0.80

1.30

1.80

2.30

2.80

0.5 1 1.5 2 2.5 3 3.5

CT (mmole/Kg)

She

ll w

eigh

t inc

reas

e fa

ctor

A. lobifera

A. lessoni

250 375125

CO32- (µµµµmole Kg -1) or

Erez unpublished

Barker and Elderfield, Science 2002

Two steps of biomineralization relevant to ocean acidification

• The supply of ions needed (Ca2+ and CO3

2-):cellular channels, pumps, or other ?

• Control of the chemical micro-environment at the site of biomineralization: e.g. pH, ionic composition, supersaturation, rate of precipitation

Why are foraminifera and corals so sensitive to atmospheric CO2 increase

while coccolithophores are not?

• In foraminifera and corals calcification is extracellular and the main source of Ca2+

and CO32- in both groups is ambient

seawater which is brought to the site of biomineralization

• Coccolithophores calcify inside vesicle that is intracellular and are using channels and pumps.

Self vacuolization in foraminifera and the

formation of delimited calcification space

v– vacuole

s – symbionts

ic- intralocullarcytoplasm

ec- extralocullarcytoplasm

d- delimited calcification space

p- pseudopods

Erez 2003

Seawater vacuolization using FITC-DexBentov et al unpublished

Two problems associated with CaCO3 precipitation from seawater

• Mg:Ca ratio in seawater is 5:1 Under these conditions aragonite in preferred kinetically (e.g. corals). How can foraminifera precipitate low Mg calcite?

• Ca:CO32- ratio is seawater is well above 10

(even at pH 9). Obviously the foraminifera are not Ca limited but carbon limited. They need a carbon concentrating mechanism .

CO2 dynamics in foraminifera

pH=9

pH=9CO2

CO2

CO2

CO2

CO2

CO2

CO2

Erez et al unpublished

Erez etalunpublished

•Acidic vacuoles supply CO2 both to symbionts and to the host’s basic vacuoles.

•Metabolic CO2 is also a source of DIC for the vacuoles

•Mg is probably removed into the cytosol and then pumped out

High CO 2

Erez 2003

Jerusalem coral reef

Horizontal growth

Completely covered colony of P. damicornis incubated with Calcein

1 cm

Erez and Braun in prep.

More evidence for direct seawater supply to the calcification site

• In addition to calcein, FITC dextran (MW 10,000, was also incorporated into skeleton of completely covered colonies

• Fluorescent plastic beads (20 nm) were incorporated into the skeleton of completely covered colonies


Pumping mechanismErez and Braun in prep.

Ca

2+ (m

M)

pH

calicoblastic

calicoblasticTime (sec)

Calicoblastic

space

Al Horani etal. 2003

pH

SW

SW

Celenteron cavity modified seawater

Aragonite skeleton CaCO3

Hermatypic coral anatomy

Oral epithelium

Aboral epithelium

MesogleaGastrodermis& symbionts

MesogleaChalicoblasticepithelium

Seawater

Seawater

High pH and Ca

?

Paracellular pathway

H+

Ca2+Ca2+ATPase

Seawater route between polyps


Summary

• Both foraminifera and corals bring seawater directly to the site of biominerlization. This is a new calcification pathway not described before

• Both groups elevate the pH at the biomineralization site (above 9)

• Ocean acidification makes it harder to elevate the pH• This may not be the case in coccolithophores which

calcify internally (in vesicles). Note that they are not labeled with Calcein

• If all the calcification in the oceans stops it will produce a CO2 sink of 0.2 (net) to 1 (gross) GTC/y. But coral reefs ecosystems will disappear

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