Marine Science Center

CaseStudy:ImpactofOceanAcidificationonMarineSpecies Part1-IntroductiontoOceanAcidificationHumanactivitiessuchasburningfossilfuelsandchangesinlandusehaveincreasedtheamountofcarbondioxide(CO2)intheatmospherefrompre-industrialslevelsof280ppmto400ppmin2018.CurrentatmosphericCO2levelsaregreaterthantheyhavebeenin800,000years,andasaresult,thefastcarboncycleisnolongerinbalance.Around25%ofcarbondioxidethatisreleasedintotheatmosphereisabsorbedintotheoceanwhichchangesthechemistryoftheocean.

TheCO2addedtoseawaterreactswiththewatermoleculeslowerthepHoftheoceanbyformingcarbonicacidinaprocessknownasoceanacidification.Thefollowingchemicalreactionistakingplaceandresultsincarbonicacid(H2CO3):

CO2(aq)+H2O→H2CO3

Carbonicacidisthesamechemicalthatgivescarbonatedbeveragestheirfizz.Carbonicacid,whenpresentinseawater,dissociatesintoH+andHCO3-.

H2CO3→ H++HCO3-

Asthehydrogenionconcentrationofseawaterincreases,theacidityincreases.ApHunitisameasureofacidityrangingfrom0-14.Thelowerthevalue,thehighertheacidityoftheenvironment.AshiftinpHtoalowervaluereflectsanincreaseinacidity.

ThecurrentpHlevelintheoceanhasdroppedfrom8.2to8.1asaresultofoceanacidification.Thismayseemlikeasmallchange,butsincepHisalogarithmicscaleitactuallyrepresentsa30%increaseinacidity.

ThefreehydrogenionproducedfromtheabovereactioncombineswithadissolvedEcoMENA

Marine Science Center

carbonateion(CO3

2-)toformanotherbicarbonateion:

H++CO3

2-→ HCO3-

Thisreactionmakeslesscarbonateions(CO3

2-)availableintheseawaterthatorganismssuchas

corals,oysters,clams,andcrabsneedtobuildahardshellorexoskeleton.

Questions

1. HowdoesthelevelofCO2intheatmosphereinfluencethepHoftheocean?

2. Howdofewercarbonateionsintheoceanaffectoceananimalsandwhatarethepotentialimpactsfororganismsthatneedtorelyonahardshellforprotection?

Part2-ImpactofOceanAcidificationonMarineOrganisms

Oceanacidificationisexpectedtoimpactoceanspeciestovaryingdegrees.PhotosyntheticalgaeandseagrassesmaybenefitfromhigherCO2conditionsintheocean,astheyrequireCO2tolive(justlikeplantsonland).Ontheotherhand,studieshaveshownthatamoreacidicoceanenvironmenthasadramaticeffectonsomecalcifyingspeciesincludingoysters,shellfish,clams,seaurchins,shallowwatercorals,deepseacorals,andcalcareousplankton.Someorganismsalsoexhibitaparaboliceffecttooceanacidification,whereshellgrowthfirstincreasesandthendropsdramatically.

Oceanacidificationcanbedescribedas“osteoporosisofthesea”.Justashumansneedcalciumtobuildtheirbones,seaanimalssuchassnailsneedcarbonatetobuildstrongshells.Thiscancausetheirshellstobecomethinnerormorebrittle.Whenshelledorganismsareatrisk,theentirefoodwebmayalsobeatrisk.Forexample,oysterlarvaeneedcarbonatetostartbuildingtheirhardshell.OysterfarmersonboththeEastandWestCoastoftheUnitedStateshavealreadyexperiencedoysterdie-offswhenlarvaeareunabletostartbuildingtheirshell.Thismulti-million-dollarindustryisexpectedtoseemoreimpactsasthepHoftheoceancontinuestolower.

Questions

Marine Science Center

1. Usingthediagramabove,giveanexampleofamarineplantoranimalthatinresponseto

oceanacidificationhas:anegativeimpactonshellgrowth,aparabolicimpactonshellgrowth,andapositiveimpactonshellgrowth.

2. ResearchersattheMarineScienceCentercanalterthelevelofcarbondioxideincontrolled

tankstoobservetheeffectofhighCO2levelsonmarinespeciessuchassnails.ThisspeciesofsnailusesitsridgestodiginthesandtoUsethediagrambelowtodescribedifferencesyouobserveinshellmorphologyandshellgrowthinhigh-CO2conditions.

3. Oceanacidificationcanhaveahugeimpactonmarinefoodwebsandfisheries.TheCO2thatweputintheatmospherecanenduphurtingmarineanimalsthatwelovetoeatandthatsupportoureconomy.Whatisonethingthatyoucandotohelpreduceyourcarbonfootprint?

MarineScienceCenterResearchersStudyingOceanAcidification

Dr.JustinRies

Dr.JustinRiesisamarinebiogeochemistintheDepartmentofMarineandEnvironmentalSciencesatNortheasternUniversity.Hisresearchprograminvestigatesawiderangeofsubjectsinthemarineandgeologicalsciences,includingglobalclimatechangeandoceanacidification.ThecommonthreadthroughoutDr.Ries'workisoceanicchange,whichheinvestigatesoverbroadtemporalscales.Bycombiningfieldstudieswithcomplementarylaboratoryexperiments,Dr.Riesisabletodirectlyexplorethebiogeochemicalprocessesthathavechangedthestateofouroceansthroughoutthegeologicpast,aswellasthosethatwilldrivechangesinthefuture.