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)

July 9, 2012 @ ICRS2012

Outline

1.Projected effects of global warming2.Projected effects of ocean acidification3.Projected combined effects of GW and OA

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 acidificationPhoto: M. Fujii

Using simplified indices and climate model outputs,

1. To project quantitatively effects of:• global warming• ocean acidificationon subtropical and temperate coral habitats

around Japan

2. To examine the combined effects of GW and OA on the coral habitats

Objective

Method

Climate model output of SST

SST as a simplified indexfor global warming

＋Climate model output

of Ωarag

＋

Ωarag as a simplified indexfor ocean acidification

Projected combined effects on corals

Projected effects of OA on corals

Projected effects of GW on corals

（ Yamano et al., 2001)

SST and Ωarag as simplified indices

（ 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)

Southern limit (caused by bleaching)•SST=30℃ line during the hottest months (Kayanne et al., 1999)

（ Yamano et al., 2001)

Climate model outputs of SST and Ωarag

SRES scenario simulations

20C3M simulations

ModelHorizontal resolution

IPSL (France)

2°× 2° ・ cosφ

MPIM (Germany)

1.5°× 1.5°

NCAR-CSM1.4 (USA)

3.6°× (0.8 ～ 1.8°)

NCAR-CCSM3 (USA)

3.6°× (1 ～ 2°) The four models results were discussed in this

study

Results1. Effects of GW on coral habitats

　

2. Effects of OA on coral habitats 　　　　　　　　　　

3. Combined effects of GW and OA on coral habitats

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 and southern limits of subtropical and

temperate coral habitats regulated by GW

Yellow: Ωarag=2.3 line as the annual lowest value (for temperate)Green: Ωarag=3 line as the annual lowest value (for subtropical)

Northern limits of subtropical and temperate coral habitats regulated by

OA

Blue: SST=18℃ line in the coldest monthsRed: Ωarag=3 line as the annual lowest valueBlack: SST=30℃ line in the hottest months (for bleaching)

Combined effects of GW and OA on subtropical

coral habitats

Blue: SST=10℃ line in the coldest monthsRed: Ωarag=2.3 line as the annual lowest value

Combined effects of GW and OA on temperate

coral habitats

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 2030s-2040s, by ocean acidification and bleaching

Temperate coral habitatsThe area is also becoming smaller, although at a less pronounced rate due to their higher tolerance for ocean acidification

Conclusions 　　　　　　　　　　　　　　　　　　　　　

　　　　　　　　　

12

Predicted SST and omega(in Tateyama (35°N, 140°E))

2000s 2010s 2020s 2030s 2040s 2050s 2060s 2070s 2080s 2090s

SS

T (

℃)

Ωara

g

SST=18℃

Ωarag=3

Marginal

Suitable

Suitable

Marginal

1. Decrease in coral calcification rates with lower CaCO3 saturation state (Ω)

Concerned effects of ocean acidification on corals

Hoegh-Guldberg (2007, Science)

2.Adverse effects on early life history stages with lower pH

dersaturate

atedundersatur

K sp

sup:1

:1

COCa 23

2

　

　

0.0

1.0

2.0

3.0

4.0

5.0

6.0

200 700 1200 1700

CO2 pCO2(μ atm)海面 分圧

Ω

飽和

度

25℃5℃

- Lower Ω with higher CO2 concentration 　　　　　　　　　　　　　　 - Lower Ω in cold waters

5℃ 25℃