1. Ocean Acidification

2. Just some facts CO 2 concentrations: preindustrial 280 ppmv 2007 385 ppmv (40% increase) CO 2 concentrations: preindustrial 280 ppmv 2007 385 ppmv (40% increase) pH of ocean: preindustrial 8.21 2005 8.10 pH of ocean: preindustrial 8.21 2005 8.10 pH is expected to drop 0.3-0.4 units at the turn of the century when CO 2 levels are expected to be 800 ppmv (IPCC) pH is expected to drop 0.3-0.4 units at the turn of the century when CO 2 levels are expected to be 800 ppmv (IPCC)

3. How does increased atmospheric CO 2 decrease ocean pH? Air-sea gas exchanges equilibrates surface water CO 2 in approximately 1 year Air-sea gas exchanges equilibrates surface water CO 2 in approximately 1 year Increased aqueous CO 2 increases bicarbonate (HCO 3 - ), and H + Increased aqueous CO 2 increases bicarbonate (HCO 3 - ), and H + Increased H + lowers carbonate ion (CO 3 2- ) and pH (pH=-log 10 [H + ]) Increased H + lowers carbonate ion (CO 3 2- ) and pH (pH=-log 10 [H + ]) CO 2(aq) + H 2 O ↔ H 2 CO 3 ↔ H + + HCO 3 - ↔ 2H + + CO 3 2- CO 2(aq) + H 2 O ↔ H 2 CO 3 ↔ H + + HCO 3 - ↔ 2H + + CO 3 2-

5. Calcifying organisms Plankton, corals, and coralline algae use CaCO 3 to form shells and skeletons Plankton, corals, and coralline algae use CaCO 3 to form shells and skeletons When CO 3 2- concentration is decreased the saturation state decreases restricting the ability of CaCO 3 (or shell) formation When CO 3 2- concentration is decreased the saturation state decreases restricting the ability of CaCO 3 (or shell) formation Dissolution rates increase as well Dissolution rates increase as well

6. Planktonic Calcification Major groups: coccolithophores and foraminifera Major groups: coccolithophores and foraminifera Coccolithophores Emiliania huxleyi and Gephyrocapsa oceanica showed a 25-66% decrease in calcification when CO 2 was 560-840μatm respectively Coccolithophores Emiliania huxleyi and Gephyrocapsa oceanica showed a 25-66% decrease in calcification when CO 2 was 560-840μatm respectively Calcidiscus leptoporus also showed a decrease in calcification rates as well as increased malformations in response to increased pCO 2 Calcidiscus leptoporus also showed a decrease in calcification rates as well as increased malformations in response to increased pCO 2

7. Planktonic Calcification Symbiot-bearing, planktonic foraminifera, had a decrease in shell mass with increased concentration of carbonate ion Symbiot-bearing, planktonic foraminifera, had a decrease in shell mass with increased concentration of carbonate ion Orbulina universa and Globigerinoides sacculifer experienced a 4-6% and 6-14% decline in shell mass when exposed to 560 and 740 ppmv CO 2 when compared to preindustrial CO 2 levels Orbulina universa and Globigerinoides sacculifer experienced a 4-6% and 6-14% decline in shell mass when exposed to 560 and 740 ppmv CO 2 when compared to preindustrial CO 2 levels

8. Impacts on corals Coral bleaching: the loss of color in corals, due to stress-induced expulsion of symbiotic unicellular algae or due to the loss of pigmentation within the algae Coral bleaching: the loss of color in corals, due to stress-induced expulsion of symbiotic unicellular algae or due to the loss of pigmentation within the algae Anthony et al. exposed three coral species to three different CO 2 levels at low and high temperatures to determine effect on bleaching Anthony et al. exposed three coral species to three different CO 2 levels at low and high temperatures to determine effect on bleaching

10. Impact on corals High CO 2 dosing (1000-1300 ppm) led to 40-50% bleaching in crutose coralline algae (CCA) and Acropora High CO 2 dosing (1000-1300 ppm) led to 40-50% bleaching in crutose coralline algae (CCA) and Acropora Intermediate CO 2 dosing (520-700 ppm) led to 30% and 20% bleaching in CCA and Acropora Intermediate CO 2 dosing (520-700 ppm) led to 30% and 20% bleaching in CCA and Acropora Present day CO 2 (380 ppm) led to a 20% and 10% bleaching in CCA and Acropora Present day CO 2 (380 ppm) led to a 20% and 10% bleaching in CCA and Acropora

11. Impacts on corals Effect of CO 2 dosing on bleaching had a stronger effect than that of temperature Effect of CO 2 dosing on bleaching had a stronger effect than that of temperature High CO 2 had a two to threefold increase in bleaching and temperature had only a 20% increase in bleaching High CO 2 had a two to threefold increase in bleaching and temperature had only a 20% increase in bleaching Lowered pH disrupts photoprotective mechanisms of symbiots by lowering rates of photorespiration and capacity for thermal dissipation Lowered pH disrupts photoprotective mechanisms of symbiots by lowering rates of photorespiration and capacity for thermal dissipation

13. Why this matters Corals responsible for high amount of productivity and bleaching results in loss of productivity Corals responsible for high amount of productivity and bleaching results in loss of productivity Disruption in ability to make shells may lower abundance of algae Disruption in ability to make shells may lower abundance of algae Loss of major food source or community shifts Loss of major food source or community shifts

14. References Anthony, K. 2008. Ocean acidification causes bleaching and productivity loss in coral reef builders. Enviromental Sciences. 105:17442- 17446. Anthony, K. 2008. Ocean acidification causes bleaching and productivity loss in coral reef builders. Enviromental Sciences. 105:17442- 17446. Doney, S. 2009. Ocean acidification: The other CO2 problem. Annu. Rev. Marine. Sci. 1:169-192. Doney, S. 2009. Ocean acidification: The other CO2 problem. Annu. Rev. Marine. Sci. 1:169-192. Orr, J. 2005. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature. 437:681-686. Orr, J. 2005. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature. 437:681-686.