Ocean acidification limits temperature-induced poleward expansion of coral habitats Yumiko Yara 1, Meike Vogt 2, Masahiko Fujii 3, Hiroya Yamano 1, Claudine Hauri 2, Marco Steinacher 4, Nicolas Gruber 2, and Yasuhiro Yamanaka 4 ( 1 National Institute for Environmental Studies ， 2 ETH Zurich ， 3 Hokkaido Univ., 4 Univ. of Bern) July 9, ICRS2012 Outline 1.Projected effects of global warming 2.Projected effects of ocean acidification 3.Projected combined effects of GW and OA

CO 2 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

Using simplified indices and climate model outputs, 1. To project quantitatively effects of: global warming ocean acidification on 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 index for global warming ＋ Climate model output of Ω arag ＋ Ω arag as a simplified index for 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 Ω arag as simplified indices （ Kleypas et al., 2006) Northern limit - Subtropical coral habitats SST=18 ℃ line during the coldest months (Yamano et al., 2001) Ω arag =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) Ω arag =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 Ω arag 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

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

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: Ω arag =2.3 line as the annual lowest value (for temperate) Green: Ω arag =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 months Red: Ω arag =3 line as the annual lowest value Black: 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 months Red: Ω arag =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 habitats The 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 SST ( ℃ ) Ω arag SST=18 ℃ Ω arag =3 Marginal Suitable Marginal

1.Decrease in coral calcification rates with lower CaCO 3 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 - Lower Ω with higher CO 2 concentration - Lower Ω in cold waters 5℃5℃ 25 ℃