ocean acidification impacts on coral reefs: changes in community … · 2008-04-08 · ocean...
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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.
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