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EcologicalEngineering35(2009)1569–1573ContentslistsavailableatScienceDirectEcologicalEngineeringjournalhomepage::ControlcountermeasuresandrecyclingexploitationarticleinfoKeywords:EutrophicationEcologicalengineeringMacrophyterestorationAlgalbloomcontrolRecyclingexploitationabstractEutrophicationisaworld-wideenvironmentalissue.LakeTaihuisatypicallarge,shallow,eutrophiclakelocatedindeltaofRiverChangjiang(YangtzeRiver).Alarge-scaleecologicalengineeringexperimenttargetedatwaterqualityimprovementwasimplementedinMeiliangBay,LakeTaihu.Inthisspecialissue,therearesixpapersrelatedtowaterpurificationandalgalbloomcontroltechniquesappliedinthisexperiment.Fourpapersaddressthevalidityandefficiencyofwaterqualityimprovementofthisecologicalengineeringandonepaperpresentsasimilarbutsmall-sizeecologicalengineering.Theothersfocusonmacrophyterestoration,aquaticplantmanagementandrecyclingexploitation.Theeditorialpaperhighlightsthemainresultsandconclusionsfromthesepapers.©2009ElsevierB.V.Allrightsreserved.Eutrophicationoflakesandreservoirsisadegradationprocessoriginatingfromtheintroductionofnutrientsfromagriculturalrun-offanduntreatedindustrialandurbandischarges.Acceleratedeutrophicationoflakesandreservoirsexperiencingduringlastcen-turyinmostpartsoftheworldrepresentsaseriousdegradationofwaterquality,notonlyinthedevelopingcountries(Teixeraetal.,1993;VanGinkel,2001;Albayetal.,2003;PyoandJin,2007),butalsoindevelopedcountries(Hawkinsetal.,1985;Kouzminovetal.,1996;Sakeretal.,1999;Geoffreyetal.,1999;Murphyetal.,2000;Alonso-Andicoberryetal.,2002).Impairmentofwaterqualityduetoeutrophicationcanleadtoaseriesofproblemsandresultinlossesofecologicalintegrity,sustainabilityandsafeuseofaquaticecosystems(NationalResearchCouncil,2000).Itischaracterizedbyfrequentlyrecurringalgalbloomswhichmaybeinedibleortoxictoconsumerspecies,causingfoodwebalterations,withpotentiallydetrimentaleffectsonbiodiversityandfisheries(Paerletal.,2001).InChina,thereare2759lakes,withatotalareaof91,019km2or0.95%oftheterritorialarea(WangandDou,1998).Aboutone-thirdoftheselakesarefreshwaterlakesmainlydistributedinthemiddleandlowerreachesofChangjiang(YangtzeRiver);allareshallowlakesandmosthavebeeneutrophicorareeutrophy-ing(Qin,2002).LakeTaihuisatypicallarge,shallow,eutrophiclakeinthisarea.Becauseofeutrophication,thenuisanceblue-greenalgalbloomcomesforthfrequentlyinthislake(Chenetal.,2003;Qinetal.,2007).Frequentlyoccurringalgalbloomsaccu-mulatingaroundtheintakeofwaterfactoriescausedcloggingandblockingofthefiltrationsystemandresultedinmillionsofpeo-plewithoutadrinkingwatersupplyattheendofMay2007(Guo,2007).InChina,macrophyterestoration,especiallysubmergedmacro-phyterestoration,wasthoughttobeaneffectiveapproachtoreducingthenutrientloadingandrestrictingalgalbloomrecur-ringinfreshwaterlakesorponds(Qiuetal.,1997;Li,1998;SunandSheng,2001;Puetal.,2001;Chengetal.,2006).Manyattemptsatsubmergedmacrophyterestorationandbioremediationhavebeenmadesincethe1980s.However,fewfreshwaterlakesweresuc-cessfullyrestoredatthelakescale.Duringexperimentalperiods,submergedvegetationinexperimentalzones(theexperimentalzonenormallyisisolatedintheopenlakebyasoftcurtain)wassuc-cessfullyrestoredandwaterqualityandclarityimprovedmarkedly.However,withtheterminationoftheexperiments,particularlythedismantlingofsoftcurtainsseparatingthetreatedenclosuresfromtheopenwater,thenewlyestablishedfragileecosystemwithflourishingaquaticplantsimmediatelycollapsed.Analysisofthesefailuresinmacrophyterestorationsuggestedthatchangesinenvironmentalconditionswhichaffectthemacrophyterestorationwereneglected.Theseenvironmentalconditionsincludehydrody-namicfactorssuchaswaves(Madsenetal.,2001;Havensetal.,2001),waterdepth(CoopsandHosper,2002;Havensetal.,2001),sedimentproperties(Scheffer,1998),nutrientloadingandperiphy-ton(IrfanullahandMoss,2004;GonzalesSagrarioetal.,2005;Qinetal.,2006a),andfishcommunities(Moss,1990;Jeppesenetal.,1990).Basedontheseunderstandings,aprincipleforsubmergedmacrophyterestorationwassuggested,i.e.,first,makingadiag-nosisofthelakeecosystemsecond,findingtheconditionswhichpreventusingmacrophytesforrestorationandthird,restoringthemacrophytes(Qinetal.,2006b).1.EnvironmentalimprovementsbasedecologicalrestorationexperimentInordertoapplytheaboveprincipletomacrophyterestora-tionineutrophiclakes,alargerscaleofsubmergedmacrophyterestorationexperimentwasconductedinMeiliangBay,LakeTaihu.TheexperimentalenclosureislocatedatthewaterintakeoftheQianlongkouwaterworksontheeasternsideofMeil-iangBay,LakeTaihu,withanareaof7km2.Inthisexperiment,environmentalconditionimprovementtechniquessuchaswave-0925-8574/$–seefrontmatter©2009ElsevierB.V.Allrightsreserved.doi:10.1016/j.ecoleng.2009.04.0031570Editorial/EcologicalEngineering35(2009)1569–1573Fig.1.AnnotatedphotographofexperimentalenclosureinMeiliangBay,LakeTaihu,China,showingmonitoringsitesS1,S2,...,S13;BAdenotestheenclosurebetweentwosoftcurtain,IDAdenotesinnerenclosure;Ydenotethesubmergedmacrophyterestorationsites.actionattenuation,algalbloomblo