Ocean acidification limits
temperature-induced poleward expansion
of coral habitats
Yumiko Yara1, Meike Vogt2, Masahiko Fujii3,
Hiroya Yamano1, Claudine Hauri2, Marco Steinacher4,
Nicolas Gruber2, and Yasuhiro Yamanaka4
(1National Institute for Environmental Studies，2ETH Zurich， 3Hokkaido Univ., 4Univ. of Bern)
Outline
1.Projected effects of global warming
2.Projected effects of ocean acidification
3.Projected combined effects of GW and OA
July 9, 2012 @ ICRS2012
CO2 increase affects corals via…
1. Global warming
Rising water temperature
Sea level rise
Stratification of surface water
Current change
Increase of extreme climate
-Physical destruction by storms
-Increases in fresh water and
terrestrial sediment and nutrient inputs by floods
-Increase in airborne dust input by droughts
2. Ocean acidification
Photo: M. Fujii
Objective
Using simplified indices and climate model outputs,
1.
•
•
on
To project quantitatively effects of:
global warming
ocean acidification
subtropical and temperate coral habitats around Japan
2. To examine the combined effects of GW and OA
on the coral habitats
Method
SST as a simplified index
for global warming
Ωarag as a simplified index
for ocean acidification
＋
＋
Climate model output
of SST
Climate model output
of Ωarag
Projected effects of
GW on corals
Projected effects of
OA on corals
Projected combined
effects on corals
SST and Ωarag as simplified indices
（Yamano et al., 2001)
（Kleypas et al., 2006)
Northern limit
- Subtropical coral habitats
• SST=18℃ line during the coldest months
(Yamano et al.,
2001)
• Ωarag=3 line as the annual lowest value (Kleypas et al., 1999)
- Temperate coral habitats
• SST=10℃ line during the coldest months (Yara et al., 2009)
• Ωarag=2.3 line as the annual lowest value (Yara et al., 2012)
al., 2001)
Southern（Yamano
limitet(caused
by bleaching)
•SST=30℃ line during the hottest months
(Kayanne et al.,
Climate model outputs of SST and Ωarag
Model
Horizontal resolution
IPSL
(France)
2°× 2°・cosφ
MPIM
(Germany)
1.5°× 1.5°
NCAR-CSM1.4
3.6°× (0.8～1.8°)
(USA)
NCAR-CCSM3
3.6°× (1～2°)
(USA)
The four models results
were discussed in this study
20C3M simulations
SRES scenario simulations
Results
1. Effects of GW on coral habitats
2. Effects of OA on coral habitats
3. Combined effects of GW and OA
on coral habitats
Northern and southern limits of
subtropical and temperate
coral habitats regulated by GW
Yellow: SST=10℃ line in the coldest months (for temperate)
Green: SST=18℃ line in the coldest months (for subtropical)
Black: SST=30℃ line in the hottest months (for bleaching)
Northern limits of subtropical and temperate
coral habitats regulated by OA
Yellow: Ωarag=2.3 line as the annual lowest value (for temperate)
Green: Ωarag=3 line as the annual lowest value (for subtropical)
Combined effects of GW and OA
on subtropical coral habitats
Blue: SST=18℃ line in the coldest months
Red: Ωarag=3 line as the annual lowest value
Black: SST=30℃ line in the hottest months (for bleaching)
Combined effects of GW and OA
on temperate coral habitats
Blue: SST=10℃ line in the coldest months
Red: Ωarag=2.3 line as the annual lowest value
Conclusions
Ocean acidification will limit a poleward shift of coral
habitats by global warming around Japan
Subtropical coral habitats
The area of suitable habitats will be reduced by half by
2020s-2030s, and is projected to disappear by 2030s2040s, by ocean acidification and bleaching
Temperate coral habitats
The area is also becoming smaller, although at a less
pronounced rate due to their higher tolerance for ocean
acidification
12
Predicted SST and omega
SST (℃)
(in Tateyama (35°N, 140°E))
SST=18℃
Suitable
Marginal
Ωarag=3
Suitable
Ωarag
Marginal
2000s 2010s 2020s 2030s 2040s 2050s 2060s 2070s 2080s 2090s
Concerned effects of ocean acidification
on corals
1. Decrease in coral calcification
rates with lower CaCO3
saturation state (Ω)
Ca  CO 

2
2.Adverse effects on
early life history stages
with lower pH
2
3
K sp
  1 : undersaturated
  1 : sup ersaturated
- Lower Ω with higher CO2
25℃
concentration
5℃
- Lower Ω in cold waters
6.0
5.0
飽和度 Ω
4.0
3.0
2.0
25℃
5℃
1.0
0.0
200
700
1200
海面CO2分圧 pCO2(μatm)
1700
Hoegh-Guldberg (2007, Science)