201131112968—2977ActaEcologicaSinicahttp//.ecologica.cn、-042010-12-162011-04-26*Correspondingauthor.E-mailcyano.shi@yahoo.com.cn“”1223*45525211.1000482.3004573.1000934.2300615.4300722007、、、。80a10。“”1。。。2、。4、。3。、pH。4。pH。FormationofcyanobacterialbloomsinLakeChaohuandthephotosynthesisofdominantspecieshypothesisJIAXiaohui12SHIDingji23*SHIMianhong4LIRenhui5SONGLirong5FANGHao2YUGongliang5LIXuan2DUGuisen11CollegeofLifeSciencesCapitalNormalUniversityBeijing100048China2CollegeofMarineSources&EngineeringTianjinUniversityofSciences&TechnologyTianjin300457China3InstituteofBotanyChineseAcademyofSciencesBeijing100093China4AnhuiCenterofEnvironmentDetectionHefei230061China5InstituteofHydrobiologyChineseAcademyofSciencesWuhan430072ChinaAbstractElucidationofthecausesofcyanobacterialharmfulalgalbloomsCHABsmaybeapreconditionfortheircontrol.WehaveinvestigatedLakeChaohusince2007identifyingphytoplanktonspeciesobservingseasonalvariationindominantspeciesmeasuringprimaryproductivitydetectingchangesinlimnologicalcharacteristicsidentifying“leadingfactors”andthenassayingtheecophysiologyofphotosynthesisinthedominantcyanobacteria.WealsoanalyzedthehistoricaleventsrelatingtoCHABsinthislake.Ourstudiesshowedthatphytoplanktondiversityvariedseasonallyanddominantcyanobacteriarepresentedmorethan74%ofthetotalphytoplanktoncells.Dominantspeciesin2008to2009includedMicrocystisviridisinAprilMayJuneOctoberNovemberandDecemberM.wesenbergiiinJulyandAugustM.aeruginosainSeptemberandAnabaenaflos-aquaeinJanuaryFebruaryandMarch.Bloomswererecordedover100yearsagointhislakeandnoappropriateexplanationshavebeenadvancedfortheircauses.Sincethehttp//.ecologica.cn1930sresearchershavepresentedthefollowingtenhypothesesonbloomformationAtheTN/TPhypothesisBtheinorganicnitrogenhypothesisCthebuoyancyhypothesisDthestoragestrategyhypothesisEthelowlighthypothesisFthehighpH/lowCO2hypothesisGtheelevatedwatertemperaturehypothesisHthetraceelementhypothesisIthezooplanktongrazinghypothesisandJtheevolutionaryadaptationhypothesis.AlthoughthesehypothesesexplainwhycyanobacteriasuccessfullycompeteovereukaryoticalgaeinmostlakesandreservoirstheycannotclarifywhydifferentdominantcyanobacterialspeciesappearinseasonalsuccessioninLakeChaohu.Anewhypothesisisneeded.Basedonourunderstandingwehaveconstructed“thephotosynthesisofdominantspecieshypothesis”asfollows1Bloomsincludevariousspeciesofcyanobacteriaandalgae.Bloominitiationisrelatedtocelldensityandalsotoprimaryproductivity.WecollectedandmeasuredphytoplanktonmonthlyindifferentwaterdepthsatsixpointsinthewesternpartofLakeChaohu.In2008to2009collectedphytoplanktonconsistedof85speciesin5phyla.Bothcelldensityandprimaryproductivitywerehighestduringthesummerandlowestduringwinter.2Duringbloomsdominantspeciesgrewmorequicklyandhadthegreatestbiomassofthephytoplankton.Therewerefourdominantspeciesandtheseconstitutedover74%ofthetotalphytoplanktoncellsindifferentseasons.3Thegrowthofdominantspecieswasaffectedbyenvironmentalfactorswetermedsome“leadingfactors”asthesehadthegreatesteffects.WhenLakeChaohubecameeutrophiclighttemperatureandpHweretheleadingfactors.4Althoughleadingfactorsaffectthegrowthofdominantspeciesphotosynthesisisthemostessentialvariable.Thestudyoftheecophysiologyofphotosynthesismayrevealtherelationshipbetweenleadingfactorsanddominantcyanobacteriaandalsoclarifywhyafewspeciesofcyanobacteriaareabletobedominantduringparticularseasons.WhentemperatureandpHincreasedbetweenspringandsummerthephotosyntheticrateofM.wesenbergiiwasgreaterthanthatofM.viridis.WhentemperatureandpHdecreasedbetweensummerandautumnthiswasfavorabletoM.aeruginosaphotosynthesis.SimilarchangesoccurredbetweenautumnandwinterandM.viridisreplacedM.aeruginosa.AlthoughA.flos-aquaewasabletogrowathighertemperaturesandpHthanM.viridisthisfilamentouscyanobacteriumwasnotabletoadapttohigherlightintensity.Lightintensityappearstobecrucialforthesecyanobacteria.Ourhypothesisisformulatedfromcommonunderstandingwithinthenaturalsciencesquestionsarisingatahigherlevelofintegrationsuchasecologyoragronomyoftenrequiremechanisticansweringatalowerintegrativelevelsuchastheecophysiologyofphotosynthesis.KeyWordscyanobacterialbloomsdominantspeciesecophysiologyofphotosynthesisthephotosynthesisofdominantspecieshypothesisLakeChaohu。、、1。。2。。、。。。80a101/3243546576pH/CO2879810911101。、、、、、。1210a。1064。1969211“”http//.ecologica.cn。。10013。。。“”123414。。、、。15。。。2007。3a、。“”。11Fig.1ThemapofsamplinginWesternAreaofLakeChaohu1.1GPS611N31°39'15.93″E117°18'3.43″、2N31°42'15.25″E117°20'18.98″、3N31°42'28.08″E117°21'44.96″、4N31°41'29.09″E117°23'50.68″、5N31°39'33.35″E117°21'40.85″6N31°35'39.03″E117°20'11.62″。2008420093。1.21.2.116-17。1000—1400。1、3、4、562。250mL00.5m1m1.5m2m1、2。。、、pH、TN、TP。“”18。1.2.2161925#64μm“∞”100mL。《———、》2021。1L1L15mL。24h30mL。。1.2.322-23YY=ni/N×finiiNfii。Y0.02。1.2.424-25BG-11CT25±1℃、80μmol·m-2·s-1。。079231http//.ecologica.cn1.2.526ClarkHansatechLtd.U.K.。2mLDC21015。ORT1。1.2.6a27a。3mL4℃6—14h4000r/min10minA665。Chlaμg/mL=13.9×A665a。1.3ExcelOriginVersion7.5OriginLabSPSS11.5。220084—20093Fig.2Monthlychangesofprimaryproductivity