珊瑚生态系统coralreefecosystem资料.docx

珊瑚生态系统coralreefecosystem资料.docx

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珊瑚生态系统coralreefecosystem资料

TheEffectofOceanAcidificationonCoralReefEcosystem

yapuwang

999619961

EcosystemandEnvironmentChange

November26,2014

Abstract

Oceanacidificationhasbecomethemostseriousenvironmentalissue,whichismainlycausedbyincreasingCO2.Thehealthoftheworld’scoralreefecosystemhasbeeninjeopardysinceindustryrevolution,astheseawaterPHlevelshavebeendestroyedandthecarbonateequilibriumhaschanged.TheIntergovernmentalPanelonClimateonClimateChange（IPCC）outlinedthatCO2levelsintheatmosphericshouldkeepataround800μL/L,asafelevelthatcouldensurethehealthofcoralreefecosystems.However,scientistspredictthatnotonlymaycoralsbemorepronetobleachingfromoceanacidificationinthefuture,butthisalsocouldinfluencethelivesofcoralreefecosystem.Scientificevidenceindicatesthattherootcauseofoceanacidificationisincreasingpressurefromglobalwarmingandhumanactivities;otherfactorsareemerging,suchassedimentationandeutrophication.

Inordertoreducethedegreetowhichoceanacidificationinfluencesseaecosystems,along-termandsystematicmonitoringsystem,includinglaboratorytestingandseaexperiments,shouldbeestablished.Atthesametime,usingphysiologyandmolecularbiologytechniques,combinedwithecologyresearchtoolstostudycoralreefecosystemsonanindividual,community,orevenawholeecosystemlevel,couldbeused.Inaddition,improvingtheadaptivecapabilityofmarineorganismsisalsoimportantinordertobepreparedtoaddresstheoceanacidificationsituationinthefuture.

Keywords:

CO2,globalwarming,oceanacidification,coralreefecosystem,calcificationrates,coralbleaching.

1.Introduction

CO2concentrationintheatmosphereplaysakeyroleonregulatingtheglobalclimatesystemanditsvariousecosystems（CrowleyandBerner,2001）.NationalOceanicandAtmosphericAdministration（NOAA）indicatedthatthefigures（Astable1shows）atMaunaLoaObservation（2011）:

beforetheindustrialrevolution,theCO2concentrationintheatmospherewasaround180-300μL/L.Sincetheindustrialrevolution,ithasincreasedto40%,aresultofclimatechange,globalwarmingandoceanacidification,whichhaveoccurredmostlyinrecentdecades.CO2intheatmospheredissolvedintheoceanbyairandwaterbeingexchangedinordertoachieveabalance,however,increasingCO2concentrationlevelsintheatmospherehavechangedtheocean’schemistry.Thishasimpactedtheoceanbybreakingtheoriginalcarbonateequilibriumsystem,reducingthePHlevelsofseawater,carbonateionconcentration,andcalciumcarbonatesaturationlevel,resultinginoceanacidification.（Kleypas,Feely&Fabry,2005）.

Sincethe1950s,increasingCO2concentrationsintheatmosphereandoceanacidificationhascausedaglobalconcern.JointGlobalOceanFluxStudy（2001）demonstratedtheoccurrenceofCO2intheatmospherediffusiontooceanandoceanacidificationdiffusionphenomenon.Oceanacidificationdirectlyaffectsthestructureandhealthofmarineecosystems.Forcoralreefs,oceanacidificationhasbecomeakeyfactor,whichdeterminesthelikelihoodofacoralreef’ssurvival,butmoreover,continuedacidificationmaytriggerthesixthmassextinction（Inversetal.,2002;Goriranetal.,1996）.ImpactoncoralreefecosystemscausedbyrisingCO2concentrationsintheatmosphereismultifaceted.Thispaperanalyzesthecurrentstudiesofeffectofoceanacidificationoncoralreefecosystemandsummarizestheminordertoprovideareferenceforfutureresearchandstudy.

2.EffectsofOceanAcidificationonCoralReefEcosystems

2.1ImpactonScleractinianCorals

Ontheonehand,scleractiniancoralsaremainbuildersofcoralreefs;ontheotherhand,itisatypicalrepresentativeofthemarinecalcifyingorganisms.Currentresearchontheeffectsoftheoceanacidificationonscleractiniancoralhavemostlyconcentratedintheareaofcalcification,ratherthanaboutotherphysiologicalprocessesofscleractiniancoralandtheimpactstheyhaveonotherbiomesincoralreefs,whicharepoorlyunderstood.ResearchshowsthatwhentheCO2concentrationinatmosphereisdouble（560μL/L）,thePHleveloftheseawater,itwillbe0.14lowerthanitisnow;calcificationrateofAcroporapalmate,Poritescoralreef,andothertypesofscleractiniancoralwilldeclineby3%to60%,andcoralreefphotosynthesisefficiencyareunlikelytochangesignificantly（Leclercq,Gattuso,Jaubert,2002）.

2.1.1TheDecreaseinTheCalcificationRateofScleractinianCoral

Therewasasimulationexperimentshowedthat,comparedwiththeglacialperiod,thecalcificationrateofscleractiniancoralwilldrop30%in2100;whencomparedwiththecurrentsituation,thecalcificationrateofscleractiniancoralwillfallby11%（Marubinietal.,2003）.Inshort,researchandexperimentsindicatethatwhenoceanacidificationintensifies,thecalcificationrateofcoralreefswilldecrease.Table2showsthatthevariationofcalcificationinPoritescoralsovertime.Calcificationwasregardedasacombinationofextension（centimetersperyear）anddensity（gramspercubiccentimeter）.Thesedataarebasedon1900–2005dataforallcolonies.（modifiedfromDe’athetal,Science,2008）.

2.1.2TheSymbiosisofCoralandTheDestructionofZooxanthellae

Inordertoprovidemorethan95%nutrientsandenergyforcoralmetabolism,symbioticalgaeabsorblightenergyandnutrientstocarryoutphotosynthesis（Muscatine,1990）.Anthony（2009）said:

“becauseofthesupplythatcomefromsymbioticalgae,coralcalcificationratecanmaintainatahighrate.”Anthony’sresearchdocumentedthatoceanacidificationcouldleadtothebleachingofcoralreefsandthedestructionofthesymbiosisofcoralandzooxanthellae.However,thecurrentsituationofoceanacidification,iscomplicatedduetotherelationshipbetweencoralreefcalcificationandphotosynthesisactivitystillbeingquitecomplicated,thus,sciencerequiresmoretimetostudytheimpactonsymbiosisbetweencoralandzooxanthellae.

2.1.3LarvaeSupplementandCommunityRecoveryWillBeMoreDifficult

Corallinealgaeplayanimportantroleforattachmentoflarvaetothescleratiniacoral.However,itisquitesensitivetooceanacidification,andresearcherspredictthatmostofcorallinealgaewilldisappearinthenexttwoorthreedecades（Heyward,Negri,1999）.Therefore,oceanacidificationwillsignificantlyimpactthecoralsexualreproductionprocess.Inaddition,undertheinfluenceofglobalclimatechangeandhumanactivities,alargenumberofcoralreefshavediedwhichhaveleftalargespacefortheinvasionalgae.Largealgaeconstraincoralreproductionandgrowth,sincealgaecompetewithcoralsforlightandlivingspace.

2.2OceanAcidificationPromotesTheDissolutionPhenomenonofTheCoralReefSystem

Oceanacidificationcannotonlyleadtoalowercalcificationrateofcoralreefsystems,butalsopromotethedissolutionphenomenonofcoralreefsystems.Someresearchesshowthateveninhealthycoralreefareas,dissolutioncontinuestooccursimultaneouslywithcalcification.Withtheincreasingofoceanacidification,thedissolutionrateofcoralreefhasrisenrapidly,sowhenthedissolutionratereachesorexceedsitscalcificationrate,somecoralreefmayexperiencenegativegrowth.Suchaphenomenonhasbeenfoundinsomedegradedmarginalcoralreefareas.Forexample,Gattuso（1997）foundthattheMooreacoralreefhaschangedtoAlgae-dominatedreefs,duetoglobalclimatechange（globalwarming）andhumanactivities（oilspill,overfertilizationandsoon）.Meanwhile,hepointedoutthattheentirecoralreefisdissolvingatarateof0.8mmolm^-2d^-1.Atthesametime,WalterandBurton（1990）performedsimilarexperimentsatacoralintertidalzoneandtheyfoundthatthiscoralreefisdissolvingatarateof13.7mmolm^-2d^-1.Dissolutionofcoralreefsisgenerallyweak,however,nearcoastalzone,dissolutionismoresevere（Kleypas,Langdon,2000）.Therefore,someunhealthycoralreefswilldissolvefirstwhenoceanacidificationbecomesmoreintense.Ontheotherhand,somehealthyreefscanoffsetthedissolvedquantitytosomeextentandpostponethearrivaltimeofthenetdissolvedstate.Buttherearealargenumberofthesimulationexperiment’sresultswhichshowthatwhentheCO2concentrationinatmospherereaches560μL/L,theseawateraragonitesaturationinthemajorityoftheworld’scoralreefareawilldropto3.0Ωargorless.Bythistime,evenhealthycoralreefswouldhaveadissolutionrateandcalcificationrateroughlyequal.Thus,mostoftheworld’scoralreefwillfaceatransitionfromanetincreaseratetoanetlossrate（Silvermanetal.,2009）.

2.3ImpactonTheOtherKeyFeaturesofBiologyinCoralReefAreas

Inrecentyears,asresearchcontinues,therearesomereportsontheimpactofoceanacidificationonotherbiologicalpopulationsintheareasofcoralreefs,asthetable3indicatesthatthemajorbiologicalpopulationsincluded:

corallinealgae,benthiccommunities,andfish.

Corallinealgaeisoneofthemostimportantmembersofcoralreefsystem,itactsas“glue”,whichhelpsacoralreefmaintainitsstabilityanditisthemostimportantfoodresourceforseaurchins,parrotfishandsomemollusks（Crowley,Berner,2001）.Meanwhile,encrustingcorallinealgaealsoprovideanimportantrigidattachmenttothebottomofcorallarvae（Crowley,Berner,2001）.However,resentstudiesshowthatoceanacidificationwillleadtoasignificantreductionofthecalcificationofcorallinealgaeandmaycausefatalconsequencesforcorallinealgae.

Benthicmollusks,bryozoansandechinoderm