2014Effectofremovaloffreefloatingmacrophytes

KnowledgeandManagementofAquaticEcosystems(2014)414,11ONEMA,2014DOI:10.1051/kmae/2014023Effectofremovaloffree-floatingmacrophytesonzooplanktonhabitatinshallowwetlandJong-YunChoi(1),Kwang-SeukJeong(1),(2),Geung-HwanLa(3),Gea-JaeJoo(1),ReceivedFebruary18,2014RevisedJune23,2014AcceptedJune24,2014ABSTRACTKey-words:submergedmacrophyte,macrophytehabitat,zooplankton,speciesdiversity,shallowwetlandSubmergedmacrophytesimprovethestructuralheterogeneityofmi-crohabitatsinaquaticecosystems,oftenprovidinganimportanthabi-tatforzooplankton.However,excessivedevelopmentoffree-floatingmacrophytesonthewatersurfacecanreducethebiomassofsub-mergedmacrophytesandresultinarelativelysimplehabitatstructure.Wehypothesizedthatcontrollingthedevelopmentoffree-floatingmacro-phyteswouldresultinamorecomplexhabitatstructurebypromotingthedevelopmentofsubmergedmacrophytes.Afterapplyingthreeex-perimentaltreatments(NR,noremoval;IR,intermediateremoval;CR,completeremovaloffree-floatingmacrophytes),wefoundthatCRoffree-floatingmacrophytesimprovedthegrowthanddevelopmentofsub-mergedmacrophytesandsupportedalargezooplanktonassemblage.However,thelargestzooplanktonassemblage(intermsofabundanceanddiversity)wasrecordedaftertheIRtreatment.AlthoughsubmergedmacrophyteswereabundantintheCRtreatment,thenumber,abundance,anddensityofzooplanktonspeciesweremuchlowerthanthoseintheIRtreatment.Preferentialselectionofdifferentmacrophytetypesbyzoo-planktonpresumablyledtovariationinplantutilizationofniches,andthesimultaneouspresenceofdifferentmacrophytelifeformscreatedacomplexmicrohabitatstructurethatinducedhighspeciesdiversityandzooplanktondensity.RÉSUMÉEffetduretraitdesmacrophytesflottantssurl’habitatduzooplanctondansleszoneshumidespeuprofondesMots-clés:macrophytessubmergés,habitatdesmacrophytes,Lesmacrophytessubmergésaméliorentl’hétérogénéitéstructurelledesmicro-habitatsdanslesécosystèmesaquatiques,offrantsouventunhabitatimportantpourlezooplancton.Cependant,ledéveloppementexcessifdesmacrophytesflottantsàlasurfacedel’eaupeutréduirelabiomassedesmacrophytessubmer-gésetaboutiràunestructuredel’habitatrelativementsimple.Nousavonssup-poséquelecontrôledudéveloppementdesmacrophytesflottantssetraduiraitparunestructuredel’habitatpluscomplexeenfavorisantledéveloppementdes(1)DepartmentofBiologicalSciences,PusanNationalUniversity,Busan609-735,RepublicofKorea(2)InstituteofEnvironmentalScience&Technology,PusanNationalUniversity,Busan609-735,RepublicofKorea(3)DepartmentofEnvironmentalEducation,SunchonNationalUniversity,Suncheon,Jeonnam540-742,Repub-licofKoreaCorrespondingauthor:[e-mail]SciencesJong-YunChoietal.:Knowl.Managt.AquaticEcosyst.(2014)414,11zooplancton,diversitédesespèces,zoneshumidespeuprofondesmacrophytessubmergés.Aprèsl’applicationdetroistraitementsexpérimentaux(pasdesuppression,suppressionintermédiaire,etlasuppressioncomplètedesmacrophytesflottants),nousavonsconstatéquel’éliminationcomplètedesma-crophytesflottantsaméliorelacroissanceetledéveloppementdesmacrophytessubmergésetfavoriseunimportantassemblagedezooplancton.Cependant,laplusgrandecommunautédezooplancton(entermesd’abondanceetdediver-sité)aétéconstatéeaprèsletraitementdesuppressionintermédiaire.Bienquelesmacrophytessubmergéssoientabondantsdansletraitementdesuppressioncomplète,lenombre,l’abondanceetladensitédesespècesdezooplanctonontétébeaucoupplusfaiblesquedansletraitementdesuppressionintermédiaire.Unesélectionpréférentielledesdifférentstypesdemacrophytesparlezooplanc-tonconduitprobablementàlavariationdel’utilisationdesnichesvégétales,etlaprésencesimultanéededifférentesformesdeviedemacrophytesacrééunestructuredemicro-habitatcomplexequiinduitunegrandediversitéd’espècesetladensitéduzooplancton.INTRODUCTIONAquaticmacrophytesarethedeterminingfactorintheoverallstructureoffreshwaterecosys-tems.Macrophytescanhavedramaticeffectsonthephysicalstructureofaquatichabitats(O’Hareetal.,2006;SmokorowskiandPratt,2007)andcreateaheterogeneousmosaicatdifferentscales.Somestudieshavesuggestedthatstructuralheterogeneityofmacro-phytesmediatestrophicinteractionsamongvariousbiota(Jeppesenetal.,1997;PeliciceandAgostinho,2006)andsignificantlyinfluencesthebiodiversityofthezooplanktoncommunity(Tolonenetal.,2005).Amonganimalsthatuseaquaticmacrophytesinfreshwaterecosys-tems,zooplanktonarelocatedatanintermediatelevelofthefoodwebandplayakeyroleintransferringenergyandmaterialswithinthefoodweb(WetzelandLikens,2000).Thus,there-lationshipbetweenhabitatcharacteristics(i.e.,macrophytes)andzooplanktonhasgraduallybecomecentraltolimnologicalresearch.Amongthevariousmacrophytelifeforms,submergedmacrophytesgenerallyincreasethephysicalcomplexityofaquaticenvironmentsandprovideasuitablehabitatforcolonizationbyzooplankton.However,free-floatingmacrophytesalsoplayafundamentalstructuralrole(Meerhoffetal.,2003).Consequently,weexpectthatthedevelopmentofdiversetypesofmacrophytes(submergedandfree-floating)willcreatemorephysicallycomplexhabitatsinaquaticecosystemsandsupporthighzooplanktonbiodiversity.Incontrast,extensivecoverbyfre