AcidOceansThreateningMarineFoodChain,ExpertsWarnTheworld'soceansareturningacidicduetothebuildupofcarbondioxide(CO2)intheatmosphere,andscientistssaytheeffectsonmarinelifewillbecatastrophic.Inthenext50to100yearscorrosive（腐蚀性的）seawaterwilldissolvetheshellsoftinymarinesnailsandreducecoralreefstorubble,theresearcherssay.FourleadingmarineexpertsdeliveredthisgrimprognosisyesterdayattheannualmeetingoftheAmericanAssociationfortheAdvancementofScienceinSanFrancisco,California.ThescientistsstressedthatincreasedoceanacidityisoneofthegravestdangersposedbythebuildupofatmosphericCO2."Oceanchemistryischangingtoastatethathasnotoccurredforhundredsofthousandsofyears,"saidRichardFeelyofSeattle'sPacificMarineEnvironmentalLaboratory."Shell-buildingbymarineorganismswillslowdownorstop.Reef-buildingwilldecreaseorreverse."Already,Feelysaid,oceanacidityhasincreasedabout30percentsinceindustrializationbeganspurringharmfulcarbonemissionscenturiesago.Unlessemissionsarereducedfromcurrentlevels,anincreaseof150percentispredictedby2100.Suchanincreasewouldmaketheoceansmoreacidicthanthey'vebeenatanytimeinthelast20millionyears,headded.SeaCreatures'UncertainFateTheorganismsmostdirectlyaffectedarethosethatbuildhardshellsorothermineralstructuresofcalciumcarbonate.Theseincludenumerousspeciesofcorals,marinesnails,andcrust-buildingalgae.AsoceansabsorbCO2fromtheair,thegasreactswithwatertoproducecarbonicacid.Theacidinturnconsumesthecarbonatethatseacreaturesneedtobuildtheirshells."Thisisaproblemthatnolivingcoralshaveencounteredintheirpastevolutionaryhistory,"saidCharlieVeron,oftheAustralianInstituteofMarineScience.Overtime,coralreefshavebeenabletoadjusttochangesinoceantemperatureandsealevel,Veronsaid.Butacidificationappearstobeaproblemthattheancestorsoftoday'scoralswereunabletosolve.Massextinctionsofmarinelifeinthedistantpast,hesaid,wereprobablycausedbychemicalchangessimilartothosehappeningtoday."Ittookcoralreefsaboutfourtotenmillionyearstorecovereachtime,"headded.Inshallowwaterswheremostcoralspresentlygrow,carbonateisnotinshortsupply.Butatgreaterdepthscarbonateconcentrationdecreasesuntilitreachesapointbeyondwhichshell-andreef-productionisnolongerpossible.Thatcriticalthresholdisrisingclosertothesurfaceasoceansgrowincreasinglyacidic,limitingthedepthsatwhichcoralsandotherorganismscanlive.Feelysaidthatthislimithasalreadyrisenseveralhundredmeters,particularlyintheIndianandPacificoceans.RecentmeasurementsintheGulfofAlaskafoundthatcarbonatewasinshortsupplylessthan325feet(100meters)belowthesurface.用心爱心专心125号编辑1JamesOrr,oftheInternationalAtomicEnergyAgency'sMarineEnvironmentalLaboratoryinMonaco,saidthatbytheendofthiscentury,shell-andreef-buildingseacreatureswillbeunabletoliveatanydepthacrossahugeareaoftheworld'soceans."Two-thirdsofcold-watercoralswillbeexposedtocorrosivewatersby2100,"Orrsaid.Far-ReachingEffectsInitialconcernsaboutoceanacidificationhavefocusedoncorals,whicharealreadyexperiencingdie-offs(相继死去)and"bleaching"duetowarmerwatertemperatures.Unfortunately,Veronsaid,"theverycoralsthatwillescapemassbleachingarethosemostpronetotheeffectsofoceanacidification."Scientistsnowrecognizethatthedangerextendstootherorganismsaswell.RobertBuddemeier,oftheKansasGeologicalSurvey,saidmineral-producing"coralline"algaeareespeciallyvulnerable.Thealgaes'cementlikesecretions（植物或动物的分泌物）arethe"glue"thathelpsholdcoralreefstogether,Buddemeiersaid,andalsohelpstabilizecoastlinesinnonreefareas.Perhapsevenmorealarmingisthethreattomarinesnailscalledpteropods.Populationsofthesetinycreaturescanreachuptotenthousandindividualspercubicmeter(35cubicfeet)intheSouthernOcean.Theirloss,Orrsaid,wouldhavefar-reachingeffects."They'reanintegralcomponentofmarinefoodwebs,ahugefoodsourceformanymarinepredators,"hesaid.Thesnails'calciumcarbonateshellsaresothintheyarevirtuallytransparent,Orradded,whichmakesthemparticularlyvulnerable."Pteropodshellscanstarttodissolvein24hours,"hesaid,"under[theseawater]conditionsweexpectfor2100."（fromNationalGeographic）Answeringthefollowingquestionsaccordingtothearticle.1.Whatdoestheunderlinedword“grim”mean?2.Listsomechangeresultedbytheoceanchemistry?3.What’sthefunctionofthealgaes'cementlikesecretions?用心爱心专心125号编辑2
