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Submergedmacrophytecommunitiesandthecontrollingfactorsinlarge,shallowLakeTaihu(China):SedimentdistributionandwaterdepthBaiLiDong,BoQiangQin⁎,GuangGao,XianLeiCaiTaihuLaboratoryforLakeEcosystemResearch,StateKeyLaboratoryofLakeScienceandEnvironment,NanjingInstituteofGeographyandLimnology,ChineseAcademyofSciences,Nanjing210008,ChinaabstractarticleinfoArticlehistory:Received20May2013Accepted3March2014Availableonline15May2014CommunicatedbyAnettTrebitzIndexwords:DepthShallowlakeSedimentconsistencyLakeTaihuEutrophicationLakeTaihu,thethirdlargestlakeinChina,issubjectedtosevereeutrophicationandcyanobacterialbloomsasaresultofdevelopmentandurbanization.Inordertorestorethedegradedlakeecosystem,itisimportanttoidentifywhichenvironmentalfactorscontrolthesubmergedmacrophyteswhichdeclinedduringeutrophication.Tocharacterizecommunitystructureofsubmergedmacrophytesandtoassesstheplant–environmentalrelationshipsinLakeTaihu,amonthlyinvestigationwasconductedfromMaytoOctoberin2010.Atotalofsixspecieswererecorded,dominatedbyPotamogetonmalaianusandVallisnerianatans.Multivariateanalysisshowedthatwaterdepth,depthofsoftsedimentsandnutrientvariables(orthophosphateofwater,organicmatterofsediment,totalnitrogenandtotalphosphorusofsediment)werethemajorfactorsdetermininggrowthandcommunitycompositionofsubmergedmacrophytesinthelake.Astrongpredictiveassociationofsoft-sedimentdepthandplantbiomassindicatedpreferenceofsubmergedmacrophytesforfirmbottomsalongtheeasternshoreandapproximately0.2mcouldberegardedasanoptimumdepthforthegrowthofplants.Thebiomassofplantsrespondedproportionatelytowaterdepth,andapproximately1.8mcouldberegardedastheoptimumdepthforthegrowthofsubmergedmacrophyteinLakeTaihu.Ourresultsindicatedthatimprovementofhabitatandtheselectionofappropriatesubmergedmacrophytesspeciesareveryimportantforecologicalrestorationinlargeeutrophiclakes.Thisstudycouldprovideusefulinformationformanagersandpolicymakerstoevaluateandmodifyrestorationpracticesinlarge,shallowlakes.©2014InternationalAssociationforGreatLakesResearch.PublishedbyElsevierB.V.Allrightsreserved.IntroductionOverthelasttwocenturies,shallowlakeshavebeensubjecttoanthropogenicalteration,eutrophicationbyincreasednutrientandsedimentloadsandalteredhydrology.Theabundanceandrichnessofaquaticmacrophytecommunitieshavedeclinedduetothesechangesinnutrientlevelsandphysicalconditions(Alahuhtaetal.,2012;BornetteandPuijalon,2011;Sondergaardetal.,2013).Theimportantrolesubmergedmacrophytesplayinthestructureandfunctioningofaquaticecosystemshasbeendocumentedinawiderangeofstudies(i.e.,Alahuhtaetal.,2013;Alexanderetal.,2008;Becketal.,2010;Chambers,1987),andalterationstomacrophytecommunitystructurewillhavecumulativeeffectsontheentirelakeecosystem(Alexanderetal.,2008;Cremonaetal.,2008).However,avoidingthelossofsubmergedvegetationinshalloweutrophiclakesandreintroducingvegetationafteritislostaredifficultchallengestomanagementpoliciesforrestorationofaquaticsystemsbecausetheseprocessesareaffectedbymanyfactors,bothbioticandabiotic(Mariaetal.,2013).Recentinvestigationshaveemphasizedtheimportanceofsedimentcomposition,trophicstatus,andinorganiccarbonavailabilityforthegrowth,distributionandspeciescompositionofsubmergedmacrophytecommunities(Cristinaetal.,2012;Kristinaetal.,2008;McElarneyetal.,2010).Severalobservationshavealsoshownthemajorroleofsedimenttextureinthegrowthanddistributionofsubmergedmacrophytes.Sedimenttextureaffectsnearlyallchemicalandbiologicalpropertiesandfunctionsofthesedimentandsoaffectsthegrowthofrootedsubmergedmacrophytes(Barkoetal.,1991;Dexter,2004;HandleyandDavy,2002).Sedimenttextureisrelatedtotherootingdepthofspeciesgiventhedifferentabilitiesofplantstophysicallypenetratesediments(Denny,1980),anditmayalsoinflu-encerootingsuccessinparticularconditionsofwaterflow(HandleyandDavy,2002;Haslam,1978).Thethicknessofthesoftsedimentlayer(hereafterreferredtoassoftsedimentdepth)reflectsthecombinedeffectsofconsistency,texture,andpenetrationresistancewhichmayinfluencethespeciescompositionofaquaticmacrophytecommunities(BornetteandPuijalon,2011;Shenetal.,2011).However,JournalofGreatLakesResearch40(2014)646–655⁎Correspondingauthorat:StateKeyLaboratoryofLakeScienceandEnvironment,NanjingInstituteofGeographyandLimnology,ChineseAcademyofSciences,73EastBeijingRoad,Nanjing210008,PRChina.Tel.:[phone].E-mailaddresses:[e-mail](B.Dong),[e-mail](B.Qin),[e-mail](G.Gao),[e-mail](X.Cai).©2014InternationalAssociationforGreatLakesResearch.PublishedbyElsevierB.V.Allrightsreserved.ContentslistsavailableatScienceDirectJournalofGreatLakesResearchjournalhomepage:fluenceofsoftsedimentdepthonplantgrowthanddistributionisnotwellunderstoodeventhoughseveralstudieshaveemphasizedtheimportanceofrapidestablishmentofsuitablesedimentforplantre-growthandsuccessioninlarge-scalerestorationofeutrophiclakes(HandleyandDavy,2002;IrfanullahandMoss,2004;Shafferetal.,1990;Yeetal.,2009).Differentspeciesofsubmergedmacrophytevaryinth