Ocean Acidification Limits Coral Habitat Shifts

1. 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 Projected effects of global warming Projected effects of ocean acidification Projected combined effects of GW and OA July 9, 2012 @ ICRS2012

2. 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

3. Objective 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

4. Method SST as a simplified index for global warming Ωaragas 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 OAon corals Projected combined effects on corals

5. SST andΩaragas 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) • Southern limit (caused by bleaching) • SST=30℃line during the hottest months (Kayanne et al., 1999) （Yamano et al., 2001)

6. Climate model outputs of SST and Ωarag The four models results were discussed in this study 20C3M simulations SRES scenario simulations

7. Results Effects of GW on coral habitats 2. Effects of OA on coral habitats 3. Combined effects of GW and OA on coral habitats

8. 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)

9. Northern limits of subtropical and temperate coral habitats regulated by OA Yellow: Ωarag=2.3line as the annual lowest value (for temperate) Green: Ωarag=3line as the annual lowest value (for subtropical)

10. Combined effects of GW and OA on subtropical coral habitats Blue: SST=18℃ line in the coldest months Red: Ωarag=3line as the annual lowest value Black: SST=30℃ line in the hottest months (for bleaching)

11. Combined effects of GW and OA on temperate coral habitats Blue: SST=10℃ line in the coldest months Red: Ωarag=2.3line as the annual lowest value

12. 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 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

14. Predicted SST and omega (in Tateyama (35°N, 140°E)) SST (℃) Suitable SST=18℃ Marginal Suitable Ωarag=3 Marginal Ωarag 2000s 2010s 2020s 2030s 2040s 2050s 2060s 2070s 2080s 2090s

15. Concerned effects of ocean acidification on corals • Decrease in coral calcification rates with lower CaCO3 saturation state (Ω) 2.Adverse effects on early life history stages with lower pH - Lower Ω with higher CO2 concentration- Lower Ω in cold waters 25℃ 5℃ Hoegh-Guldberg (2007, Science)