BiocalcificationResponses to Ocean Acidification: the Interplay of Physicochemistryand Physiology

8/18/2019 BiocalcificationResponses to Ocean Acidification: the Interplay of Physicochemistryand Physiology

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Biocalcification Responses toOcean Acidification:the Interplay of Physicochemistry and Physiology

Anne Cohenwith

Daniel McCorkle, Justin Ries, Michael HolcombSamantha de Putron (BIOS)


2/22

• Aragonite is the favored CaCO3 polymorph in today’soceans

• Skeletons made of a wide range of polymorphs;biominerals not simply precipitates from ambientseawater

• Evidence for calcifying space within which organismsmanipulate saturation state• Despite this control, as seawater Ω decreases, significant

negative impact on the ability to calcify

• Why? Predictive capabilities requires mechanisticunderstanding (corals as an example)


3/22

low & high

Mg Mix

Sea urchin tooth, Wang et al, 1997

Fish otolith, Steve Weiner CalciteAragoniteBlue mussel (Anne Cohen)

Pteropod

CaCO3 in marine skeletons and skeletal structures

VateriteGorgonian nodules, Zoe Bond

A

A

High Mg-Calcite

ACC interior,

calcite exterior.

Ascidian spicule, Joanna AizenbergHolothurian ossicle, Jefferey Simonson


4/22

Physicochemical constrains on mineralogy

Morse et al., Geology, 1997


5/22

Organisms OvercomePhysicochemical Constraints

aragonitic corals in Antarctica vaterite skeletons

Low Mg-calcite

in warm tropical

oceans


6/22

Mineralization can be intracellular, intercellular or extracellular:growing skeleton is seldom exposed directly to external seawater

intracellular

x1200

extracellular

1 mm

Scleroblasts/vacuoles Leptogorgia

(Watabe and Kingsley, 1989)

Between utricles in Halimeda segment

(Justin Ries, WHOI 2007; Torres and Baars, 1992)

Beneath tissue in corals

(Cohen and McConnaughey 2003)


7/22

Mineralization by larval oyster inunder-saturated seawater

Ω~3

20µ

m

PI

Cohen and McCorkle, 2007

Ω~0.95 Ω~0.2

•Mineralization occurs•No dissolution

•Malformations indicate disruption of normal calcification process


8/22

Seawater is sequestered into calcifying compartment


9/22

Seawater saturation state is elevated by influxof Ca2+ ions and efflux of protons

Model(Cohen and McConnaughey 2003)

Data(Al-Horani et al., 2003)


10/22

Evidence consistent with localized Ca2+-ATPaseactivity at coral mineralization site

Zoccola et al., 2004

Also in:

Coccolithophores (Klaveness, 1976); gorgonians (Kingsley and Watabe 1985)


11/22

In situ data consistent with highly supersaturated

calcifying fluid (Ωaragonite>20)

pH (total scale)

8.0 8.5 9.0 9.5 10.0

( a r a g o n i t e )

0

10

20

30

40

CO3=

only

CO3=

+ Ca

Constant DIC = 1921; S=35, T=25

(Initial alk = 2320, initial pCO2 = 280)

initial = 4.5 (pCO2 = 280)

= 21.4

(pH = 9.3, Alk = 3640)

modern = 3.8 (pCO2 = 375, Alk const)


12/22

Spherulite and crystal morphology (aspect ratio)inversely proportional to fluid saturation state

coral

Ω~4 Ω~17 Ω>25

Holcomb et al., in review


13/22

Crystal morphologies in coral dissepimentconsistent with Ω~20-30

0 10 20 30 40

seawater saturation state (omega)

0

0.5

1

1.5

2

2.5

1

/ c r y s t a l a s p

e c t r a t i o

experimental aragonite


14/22

Small changes in seawater saturation state elicit strongnegative response in many calcifiers

pH (total scale)

8.0 8.5 9.0 9.5 10.0

( a

r a g o n i t e )

0

10

20

30

40

CO3=

only

CO3

=

+ Ca

Constant DIC = 1921; S=35, T=25

(Initial alk = 2320, initial pCO2 = 280)

initial = 4.5 (pCO2 = 280)

= 21.4

(pH = 9.3, Alk = 3640)

modern = 3.8 (pCO2 = 375, Alk const)

Langdon and Atkinson JGR, 2005


15/22

Skeletal development in larval corals

planulae

innoculation

primary polyp – 7 days post-spawn

Cohen, McCorkle, de Putron 2007


16/22

Systematic decrease in extent of skeletaldevelopment (1° and 2° septa, basal plate) in 8-day

old corals with decreasing Ωaragonite

=0.2=1=2.4=3.7

Cohen et al., (in review)


17/22

Ob d d d d f l l l


18/22

Observed and predicted sensitivity of larval coralcalcification to changes in sw saturation state

0 1 2 3 4

seawater saturation state (omega)

-80

-70

-60

-50

-40

-30

-20

-10

0

% d

r o p i n s u r a c e a r e a

OBSERVED

PREDICTED

2100 AD

2300 AD

2007 AD

Cohen et al., in review Caldeira and Wickett, 2005

Systematic changes in crystal morphology of larval


19/22

Systematic changes in crystal morphology of larvalcoral aragonite with changes in Ωaragonite

A it h lit d t l h l


20/22

Aragonite spherulite and crystal morphology(1/aspect ratio) proportional to fluid saturation state

Increasing crystal growth rate

0 1 2 3 4seawater saturation state (omega)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

c

r y s t a l a s p e c t r a t i o

30

20

10

0

e s t . o m e g a c a l c i f y i n g f l u i d

Using relationship established for experimental abiogenicaragonite, estimate Ω of calcifying fluid


21/22


22/22

• Biomineralization occurs in a controlledenvironment: seawater saturation state not equal tocalcifying fluid saturation state

• Observed responses to changes in seawatersaturation state occur via (poorly understood)biological processes associated with

biomineralization• In corals (and other organisms), energetic cost

associated with raising fluid saturation state limitsgrowth rate

• In many, but not all, organisms studied - larval andadult stages - the response is negative in terms ofsurvivability/viability

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BiocalcificationResponses to Ocean Acidification: the Interplay of Physicochemistryand Physiology