Annual Reviews OnlineSearch Annual ReviewsAnnual Review of Marine ScienceOnlineMost Downloaded Marine ScienceReviewsMost Cited Marine ScienceReviewsAnnual Review of Marine ScienceErrataView Current Editorial CommitteeAll Articles in the Annual Review of Marine Science, Vol. 1Wally’s Quest to Understand the Ocean’s CaCO3 CycleA Decade of Satellite Ocean Color ObservationsChemistry of Marine Ligands and SiderophoresParticle AggregationMarine Chemical Technology and Sensors for MarineWaters:Potentials and LimitsCenturies of Human-Driven Change in Salt Marsh EcosystemsMacro-Ecology of Gulf of Mexico Cold SeepsOcean Acidification: The Other CO2 ProblemMarine Chemical Ecology: Chemical Signals and Cues StructureMarine Populations, Communities, and EcosystemsAdvances in Quantifying Air-Sea Gas Exchange and EnvironmentalForcingAtmospheric Iron Deposition: Global Distribution, Variability,and Human PerturbationsContributions of Long-Term Research and Time-Series Observationsto Marine Ecology and BiogeochemistryClathrate Hydrates in NatureHypoxia, Nitrogen, and Fisheries: Integrating Effects Across Localand Global LandscapesThe Oceanic Vertical Pump Induced by Mesoscaleand Submesoscale TurbulenceAn Inconvenient Sea Truth: Spread, Steepness, and Skewnessof Surface SlopesLoss of Sea Ice in the ArcticLarval Dispersal and Marine Population ConnectivityANRV396-MA01-08 ARI 5 November 2008 8:3Ocean Acidification:The Other CO2ProblemScott C. Doney,1Victoria J. Fabry,2Richard A. Feely,3and Joan A. Kleypas41Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole,Massachusetts 02543; email: [email protected] of Biological Sciences, California State University, San Marcos, California 92096;email: [email protected]fic Marine Environmental Laboratory, National Oceanic and Atmospheric Administration,Seattle, Washington 98115; email: [email protected] for the Study of Society and Environment, National Center for AtmosphericResearch, Boulder, Colorado 80307; email: [email protected]. Rev. Mar. Sci. 2009. 1:169–92First published online as a Review in Advance onAugust 29, 2008The Annual Review of Marine Science is online atmarine.annualreviews.orgThis article’s doi:10.1146/annurev.marine.010908.163834Copyrightc 2009 by Annual Reviews.All rights reserved1941-1405/09/0115-0169$20.00Key Wordsbiogeochemistry, calcification, carbon dioxide, climate change, coral,ecosystemAbstractRising atmospheric carbon dioxide (CO2), primarily from human fossil fuelcombustion, reduces ocean pH and causes wholesale shifts in seawater car-bonate chemistry. The process of ocean acidification is well documented infield data, and the rate will accelerate over this century unless future CO2emissions are curbed dramatically. Acidification alters seawater chemical spe-ciation and biogeochemical cycles of many elements and compounds. Onewell-known effect is the lowering of calcium carbonate saturation states,which impacts shell-forming marine organisms from plankton to benthicmolluscs, echinoderms, and corals. Many calcifying species exhibit reducedcalcification and growth rates in laboratory experiments under high-CO2conditions. Ocean acidification also causes an increase in carbon fixationrates in some photosynthetic organisms (both calcifying and noncalcifying).The potential for marine organisms to adapt to increasing CO2and broaderimplications for ocean ecosystems are not well known; both are high priori-ties for future research. Although ocean pH has varied in the geological past,paleo-events may be only imperfect analogs to current conditions.169Annu. Rev. Marine. Sci. 2009.1:169-192. Downloaded from arjournals.annualreviews.orgby UNIVERSITY OF WASHINGTON - HEALTH SCIENCES LIBRARIES on 12/30/08. For personal use only.Click here for quick links to Annual Reviews content online, including:• Other articles in this volume• Top cited articles• Top downloaded articles• Our comprehensive searchFurtherANNUALREVIEWSANRV396-MA01-08 ARI 5 November 2008 8:3ppmv: parts permillion by volumepH: a measure ofocean acidity andhydrogen ion H+concentration;pH =−log10[H+]Ocean acidification:the addition of carbondioxide in seawaterthat causes a reductionin ocean pH and shiftsin carbonate speciationHOT: Hawaii OceanTime-SeriespCO2: carbon dioxidepartial pressureDissolved inorganiccarbon (DIC): sum ofaqueous CO2gas,carbonic acid,bicarbonate, andcarbonate ionsSaturation state:thermodynamiccondition of seawaterthat describes thedegree ofsupersaturation orundersaturation withrespect to theparticular phase of theCaCO3mineralGeochemicalSections(GEOSECS):a global-scale 1970schemicaloceanography surveyCalcite: a mineralform of calciumcarbonate found inmany marine planktonand invertebrates thatis less soluble thanhigh-magnesiumcalcite, which is foundin some marine taxasuch as echinodermsand coralline algaeINTRODUCTIONOver the past 250 years, atmospheric carbon dioxide (CO2) levels increased by nearly 40%, frompreindustrial levels of approximately 280 ppmv (parts per million volume) to nearly 384 ppmv in2007 (Solomon et al. 2007). This rate of increase, driven by human fossil fuel combustion anddeforestation, is at least an order of magnitude faster than has occurred for millions of years (Doney& Schimel 2007), and the current concentration is higher than experienced on Earth for at leastthe past 800,000 years (L¨uthi et al. 2008). Rising atmospheric CO2is tempered by oceanic uptake,which accounts for nearly a third of anthropogenic carbon added to the atmosphere (Sabine &Feely 2007, Sabine et al. 2004), and without which atmospheric CO2would be approximately 450ppmv today, a level of CO2that would have led to even greater climate change than witnessedtoday. Ocean CO2uptake, however, is not benign; it causes pH reductions and alterations infundamental chemical balances that together are commonly referred to as ocean acidification.Because climate change and ocean acidification are both caused by increasing atmospheric CO2,acidification is commonly referred to as the “other CO2problem” (Henderson 2006, Turley 2005).Ocean acidification is a predictable consequence of rising atmospheric CO2and does not sufferfrom uncertainties associated with climate change forecasts. Absorption of anthropogenic CO2,reduced pH, and lower calcium carbonate (CaCO3) saturation in surface waters, where the bulkof oceanic production occurs, are well verified from models, hydrographic