coral and foraminifera calcification mechanisms in view · pdf filecoral and foraminifera...
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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
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
Schneider and Erez , 2006 Limnol &Oceanog
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
Schneider and Erez , 2006 Limnol &Oceanog
-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
Schneider and Erez , 2006 Limnol &Oceanog
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)
Schneider and Erez , 2006 Limnol &Oceanog
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
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
Erez and Braun in prep.
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
Erez and Braun in prep.
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