Climate model projections of acidification and thermal bleaching in the world’s coral reef areas Ruben van Hooidonk 1 and Jeffrey Maynard – NOAA AOML, 2 – Marine Applied Research Ctr, 3 – Cornell University; 4 – CRIOBE/EPHE/CNRS

Zooxanthellae Coral bleaching

Ocean Acidification Graphic:

Hoegh-Guldberg (1999) “ By approximately 2050 sea temperatures in tropical oceans will experience anomalies every year that will be several times those seen in 1998.” -O. Hoegh-Guldberg.

Problem and opportunity: What does our current understanding of regional and global climate and projected climate change suggest the future holds for coral reefs in my jurisdiction? ?? The objective of our collaborative work with PICCC: To produce ensemble-based projections for all four RCP scenarios for both thermal coral bleaching and ocean acidification and to make projections available as maps within a publicly accessible interactive Google Earth-based tool.

“Based on the observations used, the associated global average and median optimal DHW threshold are 6.1 DHWs.” (van Hooidonk and Huber 2009) DHWs – the accumulation of temperature stress NOAA Coral Reef Watch graphic

Temporary refugia for coral reefs in a warming world -There are few refugia from these conditions but they are temporary -Annual exceedance of 6 Degree Heating Weeks (DHWs) by 2050 Nature Climate Change (2013)

Effect of reducing/stabilising emissions

van Hooidonk, Maynard, and Planes (2013)

Opposite latitudinal gradients in projected ocean acidification and bleaching impacts on coral reefs Switch to higher bleaching threshold of 8 DHWs These conditions exceed current tolerance limits of most coral species. Global Change Biology (2013)

(a) Timing of onset of >8DHWs occurring annually (b) Ωarag at time of (a) (c) Abs value reductions in Ωarag between 2006 and (a) (d) Map in in (c) expressed as a percentage van Hooidonk et al. (2013)

Acidification and calcification

Latitude increasing High Latitude Reefs Low Latitude Reefs Degree Heating Weeks Aragonite saturation state 5%5% 5%5% Opposite latitudinal gradients in projected ocean acidification and bleaching impacts on coral reefs

Introduction page NOAA Coral Reef Watch site visitation; PICCC site on page for projections visited by people from 80+ countries

Downscaling climate model projections of coral bleaching van Hooidonk, Maynard et al. (in revision)

Downscaling climate model projections of coral bleaching

van Hooidonk, Maynard et al. (in revision) Downscaling climate model projections of coral bleaching

The future for coral reefs… ?? Image:

Thank you! Jeffrey Maynard E: Ruben van Hooidonk E: Acknowledgments: Producing these projections was made possible by a research grant awarded to our team by the Pacific Islands Climate Change Cooperative. This files contents are solely the opinions of the authors and do not constitute statements of policy, decision or position on behalf of NOAA or the U.S. Government. References: Chan, Neil, and Sean R. Connolly. "Sensitivity of coral calcification to ocean acidification: a meta‐analysis." Global change biology 19.1 (2013): Hoegh-Guldberg, Ove. "Climate change, coral bleaching and the future of the world's coral reefs." Marine and freshwater research 50.8 (1999): van Hooidonk, Ruben, et al. "Opposite latitudinal gradients in projected ocean acidification and bleaching impacts on coral reefs." Global change biology 20.1 (2014): van Hooidonk, R., J. A. Maynard, and S. Planes. "Temporary refugia for coral reefs in a warming world." Nature Climate Change 3.5 (2013):