APLab#12:DissolvedOxygenandPrimaryProductivityPaulaZdanowski,IvyZhou,KylieOHara,SaraKuramitsu

April13,2015Gold1

Mr.Hilvert

AbstractTheobjectiveofthislabwastocalculatedissolvedoxygenconcentrationanddetermine

theprimaryproductivityofanaquaticecosystem.Toaccomplishthis,thedissolvedoxygeninwateratdifferenttemperaturesfirstwasdeterminedthroughtitration.Then,tomeasuretheproductivityofanaquaticenvironment,differentbottleswithvaryingdegreesoflightwereleftunderalightfor24hours,andtitratedagaintodeterminethedissolvedoxygenconcentration.Theresultsofthislabdemonstratednostrongcorrelationbetweentheintensityofthelightandthenetproductivity,sosomethingotherthanlightmusthavebeeninfluencingtheproductivityintheaquaticenvironment.

Introduction

Oxygenisanecessarypartinaquaticaswellasterrestrialenvironments.Becauseitisneededinvirtuallyallmetabolicprocesses,dissolvedoxygenisagreatindicatorofwaterquality(Robson).Becausewaterisnotasefficientatholdingoxygenasairis,itisimperativethatoxygenisconstantlyreplenishedfromtheatmosphereandsurroundingbiologicalactivity.Thisdissolvedoxygenisabyproductofphotosynthesis.Therearevariousfactorsthatimpactthedissolvedoxygencontentofabodyofwater,includingtemperature,wind,turbulence,andthetrophicstate(HargreavesandTucker).Ameasureoftheproductionofoxygenoveraperiodoftimeisfoundbycalculatingtheamountofcarbonthathasbeenfoundonorganiccompoundsovertime(Sanchez).Theobjectivesofthisexperimentweretodemonstrateimportanceofcarbonandoxygencyclesinanecosystem,theeffectoflightandnutrientsonphotosynthesis,andtoidentifythefactorsthataffectthesolubilityofdissolvedgassesinaquaticenvironments..Wehypothesizedthatthetemperatureofthewaterwouldimpacttheamountofdissolvedoxygen,andthatthebottleswithlowerlightwouldbelessproductive.Procedure/Materials/Methods

Theobjectiveofthislabistomeasurethedissolvedoxygenconcentration,calculateproductivityandrespirationrate,anddemonstratethisknowledgeincorrespondencewiththeecosystem.Inthisfirstpartofthislab,wemeasuredtheamountofdissolvedoxygen.Todoso,wefirstpreparedasamplingwaterbottle.Wefilledabottlewith20Cwatertothetop.Wedidnotallowanyairbubblestobetrappedinsideandthencappeditbottle.Thenweplacedthebottleinawhiteshallowpanandaddedeightdropsofmanganoussulfateandeightdropsofalkalineiodide.Thesolutionwasanorangecolor.Whenwedidthis,aprecipitateformed

immediately.Nextwemixedtheingredientsbyinvertingitseveraltimes.Welettheprecipitatesettleandthenaddedonescoopofacidintothebottleandalsomixeditbyinvertingthebottle.

Whenweaddedtheacid,theprecipitatedissolvedandthesolutionturnadarkyellow.Wethenmeasured20mLofthesampleandplaceditintoatitrationvial.Apieceofwhitepaperwasplacedunderthevialtoseethecolorbetter.Next,weaddedeightdropsofstarchindicatortothesamplewhichcausedthecolortochangetoapurple.Atitrationsyringewasfilledwithsodiumthiosulfateandwasusedtotitratethesampleuntilthecolorchangedfrompurpletopaleyellow/clear.Wethenmeasuredtheamountofdissolvedoxygenbymeasuringtheamountoftitrantused.Wealsogatheredclassdata.

Inthesecondpartofthelabwemeasuredproductivity.Firstwefilledsevensamplingbottlesbysubmergingtheminthedirtygreenfishtankonthesideoftheroom.Weplacedeachbottleinsideuntilalltheairbubblescameoutandthenwecappedthebottleunderwater.Thenwelabeledeachbottlewith17.Afterwards,wewrappedthebottleswiththeappropriateamountofscreenforthelightintensities.Thiscanbeseeninthetableonpage11.(Bottle2hadfoilaroundit,bottle3had1screen,etc...)Weliedbottles27downontheirsidesunderalightovernight.Next,wepreparedawetmountofthewatersampleinbottle1andobserveditunderamicroscope.Weidentifiedtheorganismswefoundanddrewthem.Wealsopreparedbottle1thesameasthesamplebottleinthepreviousexperimentandtitratedthesolution.Onthenextdaywepreparedtheotherbottlesaccordingtothesamestepsasbeforeinthepreviouslabandbottle#1.Afterwards,wemeasureddissolvedoxygenineachbottleandtitratedeachsample.Usingspecificformulaswecalculatedtheproductivityandrespirationratesofthesamples.Classdatawasalsoobtained.Inthelastpartofthelab,wegraphedthedatagiventomeasuretheproductivityofabodyofwater.DataTable1:DissolvedOxygenConcentration,LabGroupSample

Temperature DissolvedOxygen(mg/L) %Saturation

20C 1mg/L 10%

Table2:DissolvedOxygenConcentration,ClassSample

Temperature(Celsius) DissolvedOxygen(mg/L) %Saturation

0(Group1) 0.7 5%

0(Group6) 0.9 8%

20(Group2) 0.97 10%

20(Group5) 0.88 10%

30(Group3) 0.96 12%

30(Group4) 0.75 11%

Astemperatureincreases,thedissolvedoxygenandthe%saturationalsogenerallyincreases.Table3:GrossandNetProductivity/RespirationRate,ClassSample

PercentLight DissolvedOxygen(mg/L)

NetProductivity GrossProductivity(mlO2/L)

GrossProductivity(mgC/m^3)

Initial 0.83

Dark 0.80

100% 0.79 0.04 0.01 5.36

65% 0.83 0 0.03 16.08

25% 0.78 0.05 0.02 10.72

10% 0.91 0.08 0.11 58.96

2% 0.69 0.14 0.11 58.96

Respiration=InitialBottleDarkBottleNetPrimaryProduction=LightBottleInitialBottleGrossProduction=LightBottleDarkBottleThereisnotastrongcorrelationbetweenthepercentlightexposedandthedissolvedoxygen.Thecurveincreasesanddecreasesoftensothatapatternisdifficulttoidentify.Thereisalsonospecificcorrelationbetweenlightpercentageandnetproductivityaswellaslightpercentageandgrossproductivity.

Discussion/ConclusionForPartA,ourfindingsshowthatthetemperatureofthewaterdidimpactthedissolved

oxygencontent.Theoveralltrendshowsthatthelowerthetemperature,thehigherthedissolvedoxygencontentinthewater.Thisishoworganismsinaquaticenvironmentssurviveincoldweatherwhenthewaterfreezes.Becauseofthehighoxygencontentinthewater,theyareabletoslowdowntheirmetabolisms,whilestillmaintainingahighenoughoxygenintaketosurvive.

ForpartB,ourfindingsshowthatlighthaslittleeffectontheproductivityofaquaticenvironments,whichdisprovesourhypothesis.Thereasonforthisisbecauselightcannotpenetratewaterverywell,whichmeansthatorganismslivingdeepinwaterarelimitednotbylight,butbynutrients.Thevaryingdissolvedoxygencontentsforeachbottledemonstratesthattheamountoflightdidnotreallylimittheproductivity.WorksCitedHargreaves,JohnA.,andCraigS.Tucker."MeasuringDissolvedOxygenConcentrationin

Aquaculture."TheFishSite.5mPublishing,09Jan.2006.Web.20Apr.2015.Robson,MarkG."DissolvedOxygen."Encyclopedia.com.HighBeamResearch,01Jan.2003.Web.20

Apr.2015.Sanchez,Enrique."UseoftheWaterQualityIndexandDissolvedOxygenDeficitasSimpleIndicators

ofWatershedsPollution."UseoftheWaterQualityIndexandDissolvedOxygenDeficitasSimpleIndicatorsofWatershedsPollution.ElsevierLtd.,21Nov.2005.Web.20Apr.2015.

Questions

1) Howdoestemperatureaffectthesolubilityofoxygeninwater?Thelowerthetemperature,themoresolubleoxygenisinwater.

2)Howdoessalinityaffectthesolubilityofoxygeninwater?Thehigherthesalinity,thelowerdissolvedoxygenthereisinwater.

3)Wouldyouexpecttofindhigherdissolvedoxygencontentinabodyofwaterinwinteror summer?

Iwouldexpecttheretobeahigherdissolvedoxygencontentinabodyofwaterinthewinterbecausethewateriscolder.4)Discusshoweachofthefollowingfactorscouldinfluencethedissolvedoxygen concentrationinabodyofwater:

Wind:Windwouldincreasethedissolvedoxygenconcentrationbecauseitmovesairacrossthesurfaceofthewaterallowingmoreoxygentobeintroduced.Temperature:Thehigherthetemperature,thelowertheamountofdissolvedoxygenin

water.Altitude:Asaltitudeincreases,thedissolvedoxygencontentwoulddecreasebecauseofthedropinpressure.

5)Doyouthinkitwouldbewisetostockapondwithgamefishifithadadissolvedoxygencontentof3ppm?Whyorwhynot?Itwouldnotbewisebecausemostfishneedadissolvedoxygencontentofatleast5or6ppm.

6)Ichosetolabelthelowdissolvedoxygencontentassummer,andthehighdissolvedoxygencontentaswinterbecausetemperatureisindirectlyrelatedtothelevelofdissolvedoxygeninwater.

7)InpartB,wereanyofthesampleslightlimited?Why?

Itdoesntappearthatanyofthesampleswerelightlimited,becausetherewasnotrendindissolvedoxygencontentforvaryingdegreesoflight.Thisisbecausemostaquaticenvironmentsaremorelimitedbytheirnutrientssincelightcannotpenetratedeeplyintowater.

8)BasedonyouranalysisofthelakespresentedinpartCofthelab,whichlakeismoreproductive?Lake2appearstobemoreproductivebecauselightcanpenetratedeeperintothewaterthaninlake1.

9)Whatisusedasthebasisformeasuringprimaryproductivity?DissolvedoxygencontentisusedasthebasisformeasuringprimaryproductivitybecauseitcandemonstratetheamountofO2usedinrespiration.

10)

11)a.additionofmanganoussulfate:producesmanganoushydroxidewhenaddedwithwater

b.additionofalkalineiodide:oxidizesmanganoushydroxidetomanganichydroxidec.additionofsulfamicacid:convertsmanganichydroxidetomanganicsulfated.additionofstarchindicator:makestitrationendpointmorevisiblee.titrationwithsodiumthiosulfate:freeiodinecombinesintosodiumiodide