Ocean AcidificationOcean Acidification

Just some factsJust some facts

COCO22 concentrations: preindustrial 280 concentrations: preindustrial 280 ppmv 2007 385 ppmv (40% ppmv 2007 385 ppmv (40% increase)increase)

pH of ocean: preindustrial 8.21 2005 pH of ocean: preindustrial 8.21 2005 8.108.10

pH is expected to drop 0.3-0.4 units pH is expected to drop 0.3-0.4 units at the turn of the century when COat the turn of the century when CO2 2

levels are expected to be 800 ppmv levels are expected to be 800 ppmv (IPCC)(IPCC)

How does increased atmospheric How does increased atmospheric COCO2 2 decrease ocean pH?decrease ocean pH?

Air-sea gas exchanges equilibrates Air-sea gas exchanges equilibrates surface water COsurface water CO22 in approximately 1 in approximately 1 yearyear

Increased aqueous COIncreased aqueous CO22 increases increases bicarbonate (HCObicarbonate (HCO33

--), and H), and H++

Increased HIncreased H++ lowers carbonate ion lowers carbonate ion (CO(CO33

2-2-) and pH (pH=-log) and pH (pH=-log1010[H[H++])]) COCO2(aq) 2(aq) + H+ H22O↔HO↔H22COCO33↔H↔H+ + + HCO+ HCO33

--↔ 2H↔ 2H++ + CO + CO332-2-

Calcifying organismsCalcifying organisms

Plankton, corals, and coralline algae Plankton, corals, and coralline algae use CaCOuse CaCO33 to form shells and to form shells and skeletonsskeletons

When COWhen CO332-2- concentration is concentration is

decreased the saturation state decreased the saturation state decreases restricting the ability of decreases restricting the ability of CaCOCaCO33 (or shell) formation (or shell) formation

Dissolution rates increase as wellDissolution rates increase as well

Planktonic CalcificationPlanktonic Calcification

Major groups: coccolithophores and Major groups: coccolithophores and foraminiferaforaminifera

Coccolithophores Coccolithophores Emiliania huxleyi Emiliania huxleyi and and Gephyrocapsa oceanicaGephyrocapsa oceanica showed a 25-66% showed a 25-66% decrease in calcification when COdecrease in calcification when CO22 was was 560-840560-840μμatm respectivelyatm respectively

Calcidiscus leptoporusCalcidiscus leptoporus also showed a also showed a decrease in calcification rates as well as decrease in calcification rates as well as increased malformations in response to increased malformations in response to increased pCOincreased pCO22

Planktonic CalcificationPlanktonic Calcification Symbiot-bearing, planktonic foraminifera, Symbiot-bearing, planktonic foraminifera,

had a decrease in shell mass with had a decrease in shell mass with increased concentration of carbonate ionincreased concentration of carbonate ion

Orbulina universa Orbulina universa and and Globigerinoides Globigerinoides sacculifer sacculifer experienced a 4-6% and 6-14% experienced a 4-6% and 6-14% decline in shell mass when exposed to 560 decline in shell mass when exposed to 560 and 740 ppmv COand 740 ppmv CO22 when compared to when compared to preindustrial COpreindustrial CO22 levels levels

Impacts on coralsImpacts on corals

Coral bleaching: the loss of color in Coral bleaching: the loss of color in corals, due to stress-induced corals, due to stress-induced expulsion of symbiotic unicellular expulsion of symbiotic unicellular algae or due to the loss of algae or due to the loss of pigmentation within the algaepigmentation within the algae

Anthony et al. exposed three coral Anthony et al. exposed three coral species to three different COspecies to three different CO22 levels levels at low and high temperatures to at low and high temperatures to determine effect on bleachingdetermine effect on bleaching

Impact on coralsImpact on corals

High COHigh CO22 dosing (1000-1300 ppm) dosing (1000-1300 ppm) led to 40-50% bleaching in crutose led to 40-50% bleaching in crutose coralline algae (CCA) and coralline algae (CCA) and AcroporaAcropora

Intermediate COIntermediate CO22 dosing (520-700 dosing (520-700 ppm) led to 30% and 20% bleaching ppm) led to 30% and 20% bleaching in CCA and in CCA and AcroporaAcropora

Present day COPresent day CO22 (380 ppm) led to a (380 ppm) led to a 20% and 10% bleaching in CCA and 20% and 10% bleaching in CCA and AcroporaAcropora

Impacts on coralsImpacts on corals

Effect of COEffect of CO22 dosing on bleaching had a dosing on bleaching had a stronger effect than that of temperaturestronger effect than that of temperature

High COHigh CO22 had a two to threefold increase had a two to threefold increase in bleaching and temperature had only a in bleaching and temperature had only a 20% increase in bleaching20% increase in bleaching

Lowered pH disrupts photoprotective Lowered pH disrupts photoprotective mechanisms of symbiots by lowering rates mechanisms of symbiots by lowering rates of photorespiration and capacity for of photorespiration and capacity for thermal dissipationthermal dissipation

Why this mattersWhy this matters

Corals responsible for high amount of Corals responsible for high amount of productivity and bleaching results in productivity and bleaching results in loss of productivityloss of productivity

Disruption in ability to make shells Disruption in ability to make shells may lower abundance of algaemay lower abundance of algae

Loss of major food source or Loss of major food source or community shiftscommunity shifts

ReferencesReferences Anthony, K. 2008. Ocean acidification causes Anthony, K. 2008. Ocean acidification causes

bleaching and productivity loss in coral reef bleaching and productivity loss in coral reef builders. Enviromental Sciences. 105:17442-builders. Enviromental Sciences. 105:17442-17446.17446.

Doney, S. 2009. Ocean acidification: The other Doney, S. 2009. Ocean acidification: The other CO2 problem. Annu. Rev. Marine. Sci. 1:169-192.CO2 problem. Annu. Rev. Marine. Sci. 1:169-192.

Orr, J. 2005. Anthropogenic ocean acidification Orr, J. 2005. Anthropogenic ocean acidification over the twenty-first century and its impact on over the twenty-first century and its impact on calcifying organisms. Nature. 437:681-686.calcifying organisms. Nature. 437:681-686.