Ocean Acidification: The other CO 2 problem What are the impacts on biology and biodiversity? Rob Dunbar, Stanford University Center for Ocean Solutions

Impacts on Marine Life 1)Direct effects on carbonate producers Dissolution of shells and skeletons Increased energy demand to build & maintain shells Loss of carbonate reefs Decreased biodiversity

2) Effects on many other organisms Physiological sensitivities Acidosis, reduced metabolism, torpor Reduced oxygen uptake Reduced reproductive success Compromised immune system Loss of Biodiversity (Fabry et al for review)

(Simon Wright, Australian Antarctic Division) Pristine Coccosphere of E. Huxleyi E. Huxleyi cultured in Southern Ocean under elevated pCO 2 Independent groups have now grown marine nanoalgae at elevated CO 2 levels. Sometimes the “shells” get larger but they always show defects. (Riebesell et al., 2000; Zondervan et al., 2002; Wright, 2006; Barcelos e Ramos,2009; Iglesias-Rodrigues et al., 2008, and others)

Effect of CO 2 on Sea Urchin Survival Post-Experiment Urchin Condition CO 2 Pool Control Urchins in cage near CO 2 pool Barry et al. 2003, 2004 Jim Barry (MBARI) shows that elevated CO 2 levels are lethal to sea urchins in the deep sea. At  ph ~ 0.7, spines dissolve. Other studies show decline in reproductive success.

Millions of Years Ago Tripati et al., 2009 Today (387 ppmv)

Millions of Years Ago Tripati et al., 2009 Today (387 ppmv) 2030? (450 ppmv)

LM of the diatom Asteromphalus sp. Image: Fiona Scott An example of impacts on non- carbonate organisms: Threats to the base of the food chain in the Southern Ocean Diatoms – the most important primary producer in the seas around Antarctica In cold waters, carbon chemistry dictates that increasing CO 2 levels have a greater impact on ocean acidity than in warm waters.

380 ppm CO2 800 ppm CO2 Tortell et al., 2009; Feng et al., 2009; Rose et al., 2009 Highly reproducible experiments using chemostats in Antarctic waters show major changes in relative abundances of marine plants at higher CO 2 levels.

Feely et al; Gilmer & Harbison, 2004 Pteropods (small marine snails), a major member of the Antarctic plankton, are affected as well. Multiple impacts near base of food chain lead to biodiversity loss in polar food webs.

“The prospect of ocean acidification is potentially the most serious of all predicted outcomes of anthropogenic CO 2 increase.” - J.E.N. Veron, 9/08