Ocean acidification impacts on coral reefs: changes in community … · 2008-04-08 · Ocean acidification impacts on coral reefs: changes in community structure Ilsa Kuffner, Andreas

Ocean acidification impacts on coral reefs: changes in community structure

Ilsa Kuffner, Andreas Andersson, Paul Jokiel, Ku’ulei Rodgers &

Fred Mackenzie

Florida Integrated Science CenterSt. Petersburg, Florida

Talk outlineI. Previous workII. Mesocosm study at HIMBIII. Implications for reef ecology

AcknowledgmentsVarious USGS program funding

to Kuffner; NSF funding to F. Mackenzie; EPA, NOAA and USGS funding to P. Jokiel

1980 1990 2000 2010

Experimental OA work on coral reef organisms

Single sp. Multi sp.

Beakers

Single-factor

Indoor lab

Mesocosms

Multi-factor

Outdoor

Borowitzka Mackenzie Langdon Atkinson LangdonAgegian Gattuso Marubini Leclerq

Hawaii Institute of Marine BiologyCoconut Island, Kaneohe Bay, HI

• Large-capacity open seawater system• Surrounded by active reef flat community

T

T

T

C

C

C 1 m

pCO2

Ambient

Treatment

Our approach:

1. Realistic diurnal cycles (Agegian 1985, Suzuki 1995, Ohde & Van Woesik 1999)

2. Open system (natural larval recruitment)3. Long-term (9 months)

DiurnalWeekly

Measured calcification rates (buoyant weight) and linear extension

Montipora capitata

Montipora captiata colonies

Jan - Mar Mar - May May - Jun Jun - Jul Jul - Aug overall

LSM

CaC

O3 (

mg

day-1

)

0

100

200

300

400

500

600

700

16%

did not “acclimate” to treatment; saw increase in calcification rates during summer

H1: Communities developing in tanks simulating ocean acidification would be different than control tanks

Control Treatment

CC

A (r

ecru

its m

-2d-1

)

0

40

80

120

160

C1 C2 C3 T1 T2 T3

CC

A (%

cov

er)

0

10

20

30

40

C1 C2 C3 T1 T2 T3

Non

-cal

cify

ing

alga

e(%

cov

er)

0

20

40

60

80

a

dc

b

78%

From 18%to < 2%

From 28%to 58%

Blue = control Red = OA treatment

-8

-6

-4

-2

0

2

4

6

8

Rho

dolit

h ch

ange

in m

ass

(mg

day-1

)“Rhodoliths”: free-living accretions of coralline algae

(Rhodoliths were introduced to the tanks)

Adey 1973, Littler 1985, Steneck 1986 – CCA are theprincipal calcifying framework organisms across a wide latitudinal gradient. Dominant on most hard substratum at all depths within the photic zone.

Morse 1988, Heyward 1999, Harrington 2004 – CCA are a positive settlement cue for the larvae of many species of reef-building coral (and other sessile invertebrates).

Life cycle of a coral

Planulalarva

Adult coral Coral recruit

Larval search pattern

Coral “slick”

Egg-sperm bundle

≈ 72 hours

P. H

arris

on

CCA

V. W

eis

“Brooders”

Pocillopora damicornis recruitment

(Tanks were seeded with adult colonies)

1 cm

0

10

20

30

40

50

60

70

80

90

control treatment

Cor

al r

ecru

its (m

-2)

0

1

2

3

4

Control Treatment

Cor

al r

ecru

it si

ze (m

m)

0

1

2

3

4

5

6

7

Control Treatment

Cor

al re

crui

t siz

e (#

pol

yps)

CC

A (r

ecru

its m

-2d-1

)

0

40

80

120

160

C1 C2 C3 T1 T2 T3

CC

A (%

cov

er)

0

10

20

30

40

C1 C2 C3 T1 T2 T3

Non

-cal

cify

ing

alga

e(%

cov

er)

0

20

40

60

80

a

dc

b

0

10

20

30

40

50

60

70

80

90

CCA Bare substratum Non-calcifying algae

Perc

ent c

over

controltreatment

From 25 to < 4% From 53 to 78% ND (15%)

Settlement on mesocosm walls

Other factors controlling fleshy algal abundance:HerbivoryNutrients

Balanus sp. (barnacle) recruitment

0

10

20

30

40

50

60

70

Control Treatment

Bar

nacl

es (#

per

mes

ocos

m)

0

1

2

3

4

5

6

7

Control Treatment

Bar

nacl

e di

amet

er (m

m)

Barnacles secrete low Mg-calcite (Mackenzie et al. 1983 review)

0

100

200

300

400

500

600

control treatment

Verm

etid

s (#

per

mes

ocos

m)

Vermetid recruitment (c.f. Dendropoma sp.)

p = 0.08

Most gastropods secrete aragonite (Chave, 1954)

1 cm

Vermetids + CCA = Bermuda’s “boiler reefs”

XRD analysis: surprisingly no difference!

13.6 ± 0.4 mol% MgCO3%

mol

MgC

O3

Ω, Temp, Growth rate

Agegian 1985

Main points to ponder:

OA effects on ecological processes, including recruitment and competition for space, could be substantial, at least for the ubiquitous CCA.

Will changes to community structure resulting from OA (and other stressors, e.g., high temperature) affect reef accretion rates to a greater degree than sub-lethal effects on calcification rates?

Clues to changes to community structure might lie in the carbonate mineral phase deposited by different taxa. However, can organisms change the mineral phase they deposit?

We need to account for the replacement of calcifying organisms with those that do not calcify when predicting future reef accretion rates.