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PHOSPHORUSCYCLINGINAPERIPHYTON-DOMINATED FRESHWATERWETLAND By LEONARDJOSEPHSCINTO ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOF DOCTOROFPHILOSOPHY UNIVERSITYOFFLORIDA 1997 Copyright1997 by LeonardJosephScinto IdedicatethisdissertationtotheMendicinoandScintofamilies. ACKNOWLEDGMENTS SinceregratitudegoestomyadvisorDr.K.R.Reddyandtothemembersofmy committee;Drs.W.G.Harris,G.R.Best,E.J.Phlips,andP.S.CRao.Thisworkwas partiallysupported,bothfinanciallyandwithfieldassistance,bytheSouthFloridaWater ManagementDistrict.Dr.P.V.McCormickofSFWMDdeservesspecialconsideration.I wouldalsoliketothankmyfriendsintheSoilandWaterScienceDepartmentofthe UniversityofFlorida,especiallyMs.Y.WangandMr.M.M.Fisher,fortheirsupport. Iamdeeplyindebtedtomybride,theformerMs.KirstenDeneSchneider,forher affection,support,faith,andmostlypatience.' 1 TABLEOFCONTENTS ACKNOWLEDGMENTS iv ABSTRACT viii CHAPTERS 1 INTRODUCTION 1 Periphyton 4 NeedforResearch 6 SiteDescription 7 Objectives 9 2 PHYSICOCHEMICALPROPERTIESOFPERIPHYTON,SOIL, WATER.ANDVEGETATION '. 1 Introduction 11 MaterialsandMethods 15 SiteDescription 15 WaterSamplingandAnalysis 17 PeriphytonandMacrophyteSamplingandAnalysis 18 SoilSamplingandAnalysis 19 FractionationofSoilsandBenthicPeriphyton 20 PeatAccretionRates 23 StatisticalAnalysis 24 ResultsandDiscussion 24 Water 24 Periphyton 27 J^f^t~—PLShoaonwsggp-rhtaosersrumsPeFaotrmasndinNuStoriilesntanAdccBreenttihoincRPaetreisphyton 433220 '-^-Conclusions 45 3 PHOSPHORUSUPTAKEANDPARTITIONINGBYPERIPHYTON 46 Introduction 46 MaterialsandMethods 4g StudySite 4g CharacterizationofPeriphyton 49 DevelopmentofExtractionProcedures 51 PhosphorusUptakebyPeriphyton:LaboratoryConditions 53 PhosphorusUptakebyPeriphyton:FieldConditions 55 CalculationofUptakeRates 56 TracerStudiesofPhosphorusPartitioninginPeriphyton 58 Results 59 CharacterizationofPeriphyton 59 ExtractionProcedure 59 PhosphorusUptakebyPeriphyton:LaboratoryConditions 61 PhosphorusUptakebyPeriphyton:FieldConditions 70 InorganicPuptake 70 OrganicPuptake 74 PhosphorusPartitioninginPeriphyton 74 Discussion 78 CharacterizationofPeriphyton 78 InorganicPUptake 80 OrganicPUptake 84 --^Partitioningof"Phosphorus 86 Conclusions 90 4 PHOSPHORUSFLUXBETWEENSOILANDWATERCOLUMN 92 Introduction 92 MaterialsandMethods 93 SiteDescription .-. 93 FieldExperiments 94 Dissolvedionsinporewater 94 In-situphosphorusuptake 95 GreenhouseandLaboratoryExperiments 96 DielambientDRPflux 96 FateofwatercolumnP 97 StatisticalMethods 99 Results 100 PhysicochemicalPropertiesoftheWaterColumn 100 GradientsinDissolvedPandotherIons 107 PhosphorusRemovalfromtheWaterColumn 116 Insituexperiment 116 Greenhouseexperiment 116 FateofPhosphorusUnderLightandDarkConditions 121 Disscussion 123 Conclusions 13q 5 TABHIEOWTIACTTERRACNOSLFOURMMNATIONSOFINORGANICPHOSPHORUSIN 132 Introduction 132 MaterialsandMethods 135 ^_PSihtoespDehsocrruisptPiroencipitation:PhysicochemicalConditions 113356 Laboratoryreactors 136 ChemicalCharacteristicsofWater,BPInterstitialWater,andSoil Porewater 138 Porewaterequilibrators 138 OxygenandpHProfilesofSoilColumnswithandwithoutBP 140 AnalyticalMethods 140 MineralEquilibriaCalculations 141 X-rayDiffractionofBPandSurficialSoils 142 _Re—suPClhhtoessmapinhcdoarlDuiCsshcaSurosalscutibeoirlniisttyiacssIonffWlauteenrc,edBbPyIFnltuercsttuiattiailngWaptHera,nadnCd0So2il 114422 Porewater 152 OxygenandpHProfilesofSoilColumnswithandwithoutBP 154 MineralEquilibria 154 Laboratoryexperiments 154 Insitusoilporewaterchemistry 162 X-rayDiffractionofBPandSurficialSoils 165 Conclusions 165 6 SUMMARY 167 LITERATURECITED 175 BIOGRAPHICALSKETCH 187 AbstractofDissertationPresentedtotheGraduateSchool oftheUniversityofFloridainPartialFulfillmentofthe RequirementsfortheDegreeofDoctorofPhilosophy PHOSPHORUSCYCLINGINAPERIPHYTON-DOMINATED FRESHWATERWETLAND By LeonardJosephScinto May,1997 Chairman:Dr.K.R.Reddy MajorDepartment:SoilandWaterScience Periphyton,thecommunityofmicroorganismsgrowingonsubmergedsubstrates, isaconspicuousfeatureofshallow,interiorEvergladessloughhabitats.Thisresearch wasconductedtoidentifymajorpathwaysandstoragesinvolvedinPcycling. Specifically,thisworkcenteredonmechanismsfunctioninginunimpacted,periphyton dominatedareasofthenorthernEverglades(WaterConservationArea2A).Thefieldsite wasdominatedbycalcareousblue-greenalgae(cyanobacteria). TotalPcontentwasintheorderofbenthic(BP)>epiphytic(EP)=floating(FP) periphyton,andwasintherangeof130-390mgkg"1.Calciumcarbonatecontent accountedfor20-50%ofperiphytondryweight.TotalPinBPwasapproximately equaltothatinthesurficialsoil.InorganicP(P,),associatedwithCa,washighestinthe surface0-2cmofsoilandwasdirectlyrelatedtoofincreasedCaC03depositiondueto calcificationbyBP.ThepresenceofBPonthesoilsurfacewasshowntomaintainhigher soilporewaterconcentrationsofdissolvedreactiveP(DRP)andCa2+thanwhentheBP wasremoved. Phosphorusuptakerates,measuredinthelaboratory,were0.04-0.62umolPg-' min-1(dryweightperiphyton)forEPand0.02-0.2umolPg-'min"1forBP.Uptake parametersforEPwere;V,,,^=0.85umolPg-'min-1,K^=9.9\iM,andforBPwere; vmax=°-10^mo1pg"1min-1,Km=2.5\iM.Inorganic(P;)andorganicP(P)uptake ratesbyperiphytonwashigherunderfieldconditionsthanunderlaboratorycultures. BothbioticandabioticprocesseswereshowntoregulatePuptakebyperiphyton,with CaC03asabarrierbetweenlivingperiphytonandadjacentwatercolumn.Abioticuptake accountedfor10-30%of32Pactivityinonehourand3-8%after12hours,suggestingthat PinitiallyassociatedwithCaC03surfacesisbioticallyincorporatedwithtime. InsituPuptakewasgreaterincoreswithintactBPlayers(+BP)thanincores withoutBP(-BP).Undergreenhouseconditions-BPuptakeofPwasinitiallyasrapidas +BPcores.WithcontinuedPloading-BPcoreslosttheabilitytoeffectivelyremove watercolumnP.Thissuggestsadsorptiontosoilmineralsurfaces,oruptakebysoil microbescanrapidlyassimilatePbuthavelimitedcapacityforPremoval.Partitioning 32Pinintactcores(+BP)resultedin14%abioticuptakevs.86%bioticallyincorporated. LaboratorystudieswereconductedtodetermineconditionsnecessaryforCaC03 precipitationandsubsequentPcoprecipitation.Phosphoruswasremovedfromsolution whenpH>8.6forprolongedperiods.Phosphorusreductionwasnotobservedwhen solutionpHvariedbetween7.0-8.8on12hcycles.Mineralequilibriamodeling,using SOILCHEM,generallypredictedhydroxyapatiteasthestablemineralPforminfieldand reactorsolutions.X-raydiffractionanalysisofdriedBP,andpeatsoilfrom0-2cmand2- 5cmdepthsshowedthepresenceofcalcitebutnotofmineralCa-P. Periphytonactivitycontrolsshort-termPretentionviabioticuptakeandcreates conditions,byinfluencingCa2+activity,thatincreaseslong-term,stable,abioticP retention.LossofcalcareousperiphytoncommunitieswoulddecreasetheEverglades systemcapacitytomaintainlowPconcentrations.