Table Of ContentPHOSPHORUSCYCLINGINAPERIPHYTON-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.